Popular Science Monthly/Volume 14/April 1879/Popular Miscellany

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The History of Map-making.—The President of the American Geographical Society, Judge Daly, in an address on the history of map-making previous to the time of Mercator, expressed his belief that the cartographic art is as old as, or even older than, the invention of the alphabet. The earliest map or topographical design extant, so far as we know, is the ground-plan of the town of Susa (in the Bible Shushan). This is assumed to date from the seventh century before our era. According to Strabo, Anaximander (born 612 b. c.) first represented the world in a map. The earth at that time was held to be a flat, circular plain entirely surrounded by the ocean-river. Greece was in the center of the plain. The great central sea of the inhabited region was the Mediterranean. The farthest point known on the west was the Pillars of Hercules (strait of Gibraltar). Parmenides (born 513 b. c.) is said by Diogenes Laertius to have been the first to assert the sphericity of the earth, and that it is situate in the center of the universe. Strabo credits Parmenides also with having been the first to divide the globe into five zones, or climates as they were called. Passing lightly over the twelve centuries between Ptolemy and the awakening of maritime enterprise which led to the discovery of America, Judge Daly spoke of the large map of the world constructed in Venice in 1457 by Fra Mauro. This map was painted on the wall of a convent in Venice, and it is remarkable not only for the extent of the geographical information it embodies, but for the artistic skill with which it is executed. But even the maps constructed after the time of Columbus and Magelhaens in their delineation of the outline of countries were very defective, and especially in respect to the American Continent. The accessories to geographical knowledge had become so vast, that the work of giving the whole surface of the earth as far as known, in all its details, with any approximation to correctness, was not accomplished till Mercator produced his great map of the world in 1569. In this map he introduced what has ever since been known as Mercator's projection, which not only gives the world in one view, but by a very curious and simple contrivance showed the most effectual way for a vessel to sail on a straight line over a curved surface, and thereby solved what was before one of the most difficult problems in navigation.

Fiords of Glacial Origin on Long Island.—In a paper by Mr. E. Lewis, Jr., read before the Natural History Section of the Long Island Historical Society, some account is given of the fiords which occur on the north side of Long Island, bordering Long Island Sound. In a distance of fifty miles eight of large size occur, penetrating the island to near its center. There are several small ones, remains evidently of large valleys that have been shortened by wearing away of the banks at the sound-shore. The waters of the sound extend into the large valleys from two to six miles, forming safe and beautiful harbors. Fiords, common on rocky coasts, like those of Maine or Greenland, are not frequent in the drift, but those described are singularly perfect in form. They are simply long, deep valleys, from half a mile to a mile broad, their source being in the hill region of the central part of the island. The depth of water in the deep portions of the fiords is from ten to thirty feet, but in a few places where the tidal currents are rapid depths of forty and even fifty feet are found. It is quite certain that sediment is slowly accumulating in the harbors, and is already of considerable thickness. Piles have been driven in one instance through forty feet of soft ooze, and meadows now occupy the upper portions of the valleys. The banks vary in elevation. The general elevation of the country throughout the region may be 150 feet above tide, but it is very undulating, being traversed by a great number of small lateral valleys, which open into the great fiords, chiefly on their easterly side. On the west side of Hempstead Harbor (Roslyn) the bank is 250 feet high, and at one point known as "Beacon Hill" attains an elevation of 307 feet. If to this height we add the depth of water and of sediment in the harbor, it will show that the extreme depth of the valley was not less than 350 feet when its bottom was swept by a glacial stream. There is reason to believe that in several instances these fiord valleys were once continuous southward to the ocean, and the site of glacial rivers flowing in that direction. They probably became filled with débris from the melting glacier, as it finally yielded to a change of climate. From that time the discharge of glacial water was northward through what is now Long Island Sound. The conclusion is, that nearly all the fiords in question are not eroded valleys, but are what remains of river valleys, maintained as such, while the deposit of drift went on. The lateral, or small valleys, referred to were mainly produced by erosion, but why they occur so largely on the easterly side of the great fiords is not explained.

Rainfall and Sun-spots.—The relation between rainfall and sun-spots is a subject which has been discussed with no little heat for a few years past. Of speculation and theory there is more than enough, and it is time to collect and note the facts. Here is a table showing the readings of the Nilometer for thirteen years, from which it is clear that the river Nile, during that time at least, does not confirm the rule, "Maximum spots, maximum rainfall":

Years. Depth of the Nile.
1866 28¼ feet minimum spots.
1867 24½ "minimum spots.
1868 19 "
1869 29¼ "
1870 25½ "
1871 23¼ "
1872 25½ "maximum spots.
1873 20 "
1874 29 "
1875 24 "
1876 25 "
1877 18 "minimum spots.
1878 30 "

The Vertebral Articulations in Birds.—Professor Marsh, in the "American Journal of Science and Arts" for April, essays an explanation of the peculiar saddle-shaped articulation seen in the vertebræ of birds. Between Ichthyornis and Hesperornis, two birds with teeth from the Cretaceous, there is the widest conceivable difference as regards this part of the skeleton, in Hesperornis the ends of the centrum being saddle-shaped, as in ordinary birds, while in Ichthyornis the articulation of the centrum is cup-shaped. But in the third cervical vertebra of Ichthyornis, Professor Marsh catches nature in the act, as it were, of forming a new type, by modifying one form of vertebra into another. Following this hint, the connection between these widely divergent types of structure soon becomes apparent, and the development of the modern form of avian vertebra from the fish-like biconcave form finds a solution. In the anterior articulation of this vertebra of Ichthyornis the surface looks downward and forward, being inclined at an angle of nearly 60° with the axis of the centrum. In vertical section it is moderately convex, while transversely it is strongly concave, thus presenting a near approach to the saddle-like articulation. None of the other vertebræ of Ichthyornis possesses this character. "This highly specialized feature," remarks Professor Marsh, "occurs at the first bend of the neck, and greatly facilitates motion in a vertical plane. If, now, we consider for a moment that the dominant motion in the neck of a modern bird is in a vertical plane, we see at once that anything that tends to facilitate this motion would be an advantage, and that the motion itself would tend directly to produce this modification. With biconcave vertebræ, the flexure in any direction is dependent on the elasticity of the fibrous tissue that connects them, as the edges of the cup do not slide over each other. An increasing movement in the neck of Ichthyornis in a vertical plane would tend to deflect the upper and lower margins of the circular cup, and to produce a vertical constriction, and at the same time to leave the lateral margins projecting; and this is precisely what we have in the third vertebra. This modification of the vertebræ would naturally appear first where the neck had most motion, viz., in the anterior cervicals, and gradually would be extended down the neck; and, on to the sacrum, if the same flexure were continued. Behind the axis, or where the vertical motion prevails, we find in modern birds no exception to the saddle articulation in the whole cervical series. In the dorsal vertebræ, this cause would be less efficient, since the ribs and neural spines tend to restrict vertical motion, and hence to arrest this modification. This region, then, as might be expected, offers strong confirmatory evidence of the correctness of the above explanation; for here occur, among modern birds, the only true exceptions known in the presacral series to the characteristic saddle-shaped articulation."

Professor Tyndall on Sound.—Professor Tyndall is this season giving a course of lectures on sound at the London Royal Institution. In the first lecture he illustrated by many experiments the action of sound-waves, and explained the mechanism of the ear. In treating of the velocity of sound, he said that at the temperature of 32° Fahr. air conveys sound-waves 1,090 feet per second, but that this rate varies with every variation of the temperature. It is well known that, when a mechanically striking bell is placed under a receiver exhausted of air, no sound is heard. Professor Tyndall showed by experiments that when a little air, about one fourth, is admitted into the receiver, the sound is feeble only; but on introducing a little hydrogen, the sound was again stilled. This fact was known to Sir John Herschel, and he gave the explanation that hydrogen breaks the continuity of the medium. But this is not the true explanation. Professor Stokes, paying attention to the fact that when a tuning-fork is struck and held in air it gives out but little sound, investigated the subject, and arrived at the conclusion that air is so mobile that it runs around the tuning-fork without being thrown into waves. Check this "running round" by holding a card at one side of the fork, and the sound is augmented. Now, hydrogen is more mobile still than air, and hence the probable explanation of the bell not sounding in it is, that the hydrogen "runs round" so readily that it is not thrown into waves. Alluding to Newton's attempt to reconcile his theoretical calculation of 916 feet per second with the experimental results of 1,090 feet per second as the velocity of sound. Professor Tyndall said that the philosopher had forgotten to take into account the heat developed by the sound-wave in its own path. By the aid of the thermopile and galvanometer arrangement, the lecturer showed that a very gentle and small compression of air does produce heat. Several experiments to show the passage of sound through wood, water, and other bodies were made in the concluding part of the lecture. In one of these experiments music played in the cellars of the Institution was made audible by a connecting wooden rod rising into the lecture-hall, a common wooden tray being alternately held on the top of the rod and removed again. The rod itself had not surface enough to give vibrations which can be heard, but the larger surface of the tray gave the "magic music."

An ingenious and very simple method of measuring the velocity of sound in air and other gases is described by M. Bichat, in the "Journal de Physique." A tube about ten metres long, made of tin plate, is bent so that its extremities A and B are near together. The end A is closed by an India-rubber membrane; the end B carries a cork with a glass tube through it, which communicates, by means of an India-rubber tube, with a Marey's manometric capsule. These capsules are arranged in front of a blackened cylinder, so that the extremities of their levers rest upon the same generating line. Close by these a tuning-fork, making one hundred vibrations per second, is placed, and inscribes its vibrations side by side with those of the manometric capsules. The experiment being so arranged, a slight shock is given by the hand to the membrane A, the blackened cylinder meantime being turned. The capsules register the point of departure and the point of arrival, while the tuning-fork gives the time. In this way the velocity of sound in air was found by M. Bichat to be 333.3 metres per second. By means of two tin tubes, placed one above the other, we may in a single experiment demonstrate the difference of velocities of sound in air and in hydrogen; but it is difficult, in consequence of diffusion through the India-rubber, to keep the tube full of pure hydrogen.

Recent Exploration of Wyandotte Cave.—Wyandotte Cave, in Crawford County, Indiana, has a total length of twenty-three miles, including all the avenues; it includes many fine halls and domed chambers, the largest of which has a circumference of one thousand feet, and is said to be two hundred and five feet high. The Rev. H. C. Hovey mentions, in "The American Journal of Science," an important discovery made in this cave last April by a party of students from Wabash College. Forcing their way through a low, narrow passage from the locality known as Rugged Pass, the party entered a realm of chaos. "Pits, miry banks, huge rocks, are overhung by galleries of creamy stalactite, vermicular tubes intertwined, frozen cataracts, and all, in short, that Nature could do in her wildest and most fantastic mood." One of the curiosities of this place is a row of stalactites on which a musical chord can be struck or a melody played. What is known as the "Old Cave" was worked by saltpeter miners in 1812, and sundry acts of vandalism have been charged on them which more probably were done by the aborigines. The finest stalacto-stalagmitic column probably in the world is the Pillar of the Constitution in this "Old Cave." It is forty feet high, twenty-five feet in diameter, and it rests on a base three hundred feet in circumference. The weight of this immense mass of alabaster caused the underlying rocks to settle, and this in turn cracked the base, causing great crevices. At some former time a large segment was cut from the base of this column. Starting from one of these crevices, an excavation was made, cutting a mass from the base having an arc of thirty feet, and making a cavity in the pillar itself ten feet wide, seven feet high, and five feet deep. This excavation has hitherto been regarded as a deliberate attempt of the miners to fell the column, but Mr. Hovey thinks the work must have been done a thousand years ago.

Commercial Products of New Caledonia.—M. Jules Gamier, who has spent three years in New Caledonia investigating its mineral resources, states that all the principal vegetable productions of the tropics grow well on that island, though, with the exception of coffee and tobacco, they are subject to periodical destruction by invasions of grasshoppers. Cotton, moreover, is liable to damage during the rainy season, which, coinciding with the gathering of the crop, destroys the produce. There are several native oil-yielding plants, and the culture of the mulberry and silkworm have been introduced with success. The forests contain many useful timber-trees; but the most active industry is the raising of cattle, in which an active export trade is carried on with Australia. Of other animal products there is nothing of commercial value except the fish, which are abundant and of great variety. The chief source of wealth in the island is, however, its metallic products. It is rich in gold, copper, and nickel, the latter presenting itself in the form of a magnesian hydro-silicate, called by Professor Dana Garnierite. The native inhabitants number thirty-five thousand, and the whites seventeen thousand. The recent insurrection will not interfere with the progress of the colony.

Professor A. Agassiz's Zoological Laboratory.—Professor Alexander Agassiz's zoological laboratory at Newport is admirably contrived to accommodate a small number of workers. It is forty-five by twenty-five feet. The whole of the northern side of the floor, upon which the work-tables and microscope-stands are placed, is supported on brick piers and arches independent of the brick walls of the building. The rest of the floor is supported entirely on the outside walls and on columns on the north side. This gives to the microscopic work the great advantage of complete isolation from all disturbance caused by persons walking over the floor. The material for the laboratory procurable at Newport is abundant. The dredging is fair and not difficult, as the depth in the immediate neighborhood does not exceed twenty to thirty fathoms. The pelagic fauna, however, is the most abundant. During the course of each summer, by the use of the dip-net, representatives of all the more interesting marine forms can be found. The laboratory stands on a point at the entrance of Newport Harbor, past which sweeps the body of water brought by each tide into Narragansett Bay, and carrying with it everything which the prevailing southwesterly wind drives before it. Newport Island and the neighboring shores form the only rocky district in the long stretch of sandy beaches extending southward from Cape Cod—an oasis, as it were, for the abundant development of marine life along its shores.

Making Sound-Vibrations visible.—A very ingenious method of recording articulate vibrations by means of photography has just been invented. The apparatus (says "Galignani's Messenger") consists of a steel mirror capable of oscillations on a diametral axis, to the back of which is attached a lever connecting it with the center of a telephone-disk arranged with an ordinary mouthpiece. Whenever the disk is made to vibrate, the mirror oscillates with it, and a beam of sunlight thrown on the reflector from a heliostat describes lines of light on a suitably prepared screen. If the latter be movable at right angles to those lines of light, and carries a collodion film, the oscillation of the light is recorded on the prepared surface as a more or less complex curve having the peculiarity of the sound-wave which caused each particular motion. Another and simpler phoneidoscope is suggested by a writer in "Nature": it may be made without the aid of any apparatus whatever, by bending the forefinger and thumb of one hand so as to form a circle, and then with the other hand drawing over the aperture a film of soapsuds. By turning the wrist, the angle made with the direction of the light may be readily adjusted; a motion of the elbow alters the distance from the mouth, and the tension of the film can be exactly regulated by moving the thumb and finger. On singing or speaking to the film when in proper tension, beautiful figures appear, which may be reflected direct from the film on a screen. The experiment is extremely curious and interesting.

George Bidder, the "Calculating Boy."—There died lately in England a man of prodigious arithmetical power, whose mental faculties would afford matter for profound research to the psychologist. George Bidder made his mark in early life as a "calculating boy"; but in him one overgrown faculty did not eclipse all the other mental powers, for throughout life (he died aged seventy-two years) he evinced first-rate business ability, and in fact accumulated a large fortune by his own exertions. Nor did his mathematical faculty decline as his other powers matured; to the last he was capable of the same astonishing feats of calculation which made him remarkable as a boy. Instances of his extraordinary powers are given in a letter written by James Elliot, Professor of Mathematics in Queen's College, Liverpool, who was Bidder's fellow student in Edinburgh. Of these we quote two: A person might read to Bidder two series of fifteen figures each, and, without seeing or writing down a single figure, he could multiply the one by the other without error. Once, while he was giving evidence before a Parliamentary committee, counsel on the opposite side interrupted him with, "You might as well profess to tell us how many gallons of water flow through Westminster Bridge in an hour." "I can tell you that too," was the reply, and he gave the number instantaneously.

Certain interesting facts are mentioned with regard to the possession of the same or similar powers by members of Bidder's family. His eldest son, who is a successful barrister, can play two games of chess simultaneously without seeing the board. Like his father, he can multiply fifteen figures by fifteen without seeing them, but by a peculiar process. One of the grandsons showed a very marked degree of mechanical ingenuity. Even the granddaughters possess extraordinary powers of calculation. George Bidder's elder brother, a Unitarian minister, was not remarkable as an arithmetician, but had an extraordinary memory for Bible texts, and could quote almost any text in the Bible, and give chapter and verse. Another brother was an excellent mathematician, and was actuary of a great life-insurance company.

Peruvian Antiquities.—In an article on Peruvian antiquities, published in the "Kansas City Review of Science and Industry," Dr. E. R. Heath gives an interesting account of the vast wealth of ruins with which the land of the Incas is overstrewed. Go where you will in Peru, and relics of the past meet your eye either in ruined walls, watercourses, terraces, or extensive areas covered with broken pottery. Dr. Heath takes as an illustrative instance the Jequetepeque Valley. Here the bottom-lands of the river are from two to three miles in width, with a southern sloping bank, and the northern a perpendicular one nearly eighty feet high. Beside the southern bank, near the point where the river empties into the sea, is an elevated platform, one quarter of a mile square and forty feet high, all of adobe. A wall, fifty feet wide, connects it with another distant a few hundred yards, which is 150 feet high, 200 feet across the top, and 500 feet at the base, and nearly square. This latter structure was built in sections or rooms ten feet square at the base, six feet at the top, and about eight feet high. These rooms were afterward filled with adobes, then plastered on the outside with mud and washed in colors. All the Peruvian mounds of this class have on the north side an incline as a means of access. On the north side of the river, on the top of the bluff, are the ruins of a walled city two miles wide by six miles long. In following the river to the mountains you pass ruin after ruin, one artificial mound (huaca) after another. At Tolon, a town at the base of the mountains, the valley is crossed by walls of bowlders and cobble-stones, ten, eight, and six feet high, one foot to eighteen inches wide at the top and two to three feet at the base, inclosing the ruins of a town one quarter of a mile wide and more than a mile long. At this point the railroad enters the Jequetepeque Valley. For eight miles it crosses a barren sand-plain of more than fifteen miles in length, covered with ruined walls, water-courses, dead algaroba and espino trees, with fragments of pottery and sea-shells, even to nine feet in depth, mixed with the sand. The bases of the mountains have, in a good state of preservation, many thousand feet of an old watercourse, while their sides to the perpendicular parts are lined with terraces. This watercourse, now dry, can be traced for the distance of forty-five miles.

Important Discovery in Entomology.—Mr. Gray, of Albany, has been engaged in the study of our diurnal Lepidoptera for many years. He has made the discovery, as published in the "Canadian Entomologist," that our Eastern species of Liminitis, four in number, are not distinct. They belong to a single plastic genetic group, of which arthemis is the most northern, proserpina intermediate between arthemis and ursula, and the red disippus the most southern. He has collected them in vertical altitudes on hills in the Middle States and New England, and has intermediary specimens half bluish and red between the two most strikingly contrasted species of the group ursula and disippus. This discovery is the most remarkable in the group announced since the recognition of the female form of diana by Mr. W. H. Edwards. In general interest it far surpasses that discovery, and we expect will be more generally noticed.

California Climates and Consumption.—The conditions requisite in a health resort for consumptive patients are relative dryness of atmosphere and an agreeable and equable temperature throughout the year. There are in the State of California a number of localities in which these conditions are happily combined, and which afford to the consumptive opportunity for living out-of-doors at all seasons. In the "Alta California Almanac" is published a table setting forth the mean relative humidity, and mean temperature, summer and winter, of the most noted sanitaria in the State, from which we make a few selections. The places which have the least humidity are Atlas Peak and Blakes, the former 1,500 feet above sea-level, and the latter 2,100, and both situated in a mountain-ridge east of Napa Valley. This ridge is thirty miles from the sea, is seldom covered by fog, is beyond the reach of the cold sea-breezes, and is warmer in winter and cooler in summer than the valleys on each side. At Atlas Peak the relative humidity is in summer 39°, in winter 51°—"summer" standing for the "dry season" from May to October, and "winter" for the "wet season" from November to April, inclusive. The mean temperature for January at Atlas Peak is 50° Fahr., and for July 74°. At Blakes the relative humidity for summer is 39°, and for winter 60°; and the mean temperature for January is 45°, for July 73° Fahr. These two localities are only a few miles distant from one another, and are within five or six hours' travel from San Francisco, Other localities are represented in the table as follows:

Summer. Winter. January. July.
Camp Apache. 57° 56° 38° 84°
Visalia. 42 72 45 80
Anaheim 64 60 50 68
Fort Yuma. 58 68 56 97
Los Angeles. 66 64 52 75
Santa Barbara. 71 67 53 68
San Diego. 75 69 51 72
San Rafael. 65 83 48 67

Resurvey of Yellowstone Park.—A good summary of the work done by Hayden's Survey of the Territories during the season of 1878 is published in the "Naturalist," from which we learn that the personnel of the Survey was divided into four parties: one for the extension of the primary triangulation northward, two for topographical and geological work, and one for photography and special work in geology. All the parties left the Union Pacific Railroad at Point of Rocks and Green River stations about July 25th, and proceeded northward toward the Yellowstone National Park. To the second division was assigned the duty of making an exhaustive survey of the park and its surroundings, and to the third the exploration of the Wind River range and the Snake River country. The primary triangulation was extended over about 12,000 square miles. Materials were collected for a topographical map of the Yellowstone Park, on the scale of one mile to an inch. Its geology was studied minutely. A peak of the Wind River range, named Fremont's Peak, was found to be over 14,000 feet in height above the sea; no trace could be seen of the presence of man on its summit at any time. Three glaciers were discovered on the east side of the Wind River Mountains. The object of again surveying the Yellowstone Park was to bring it under the system of triangulation, which has been very successfully employed in Colorado, and to make the entire work uniform. All the old hot-spring basins were resurveyed and mapped, soundings and temperatures of several thousand hot springs were made, and the action of the geysers carefully studied. Over fifty fine photographic views were obtained of the bowls and other curious ornamental details of the Hot Springs.

The Personal Equation.—One of the principal defects of "our primary mathematical instrument," the human mind itself with its organic apparatus, is very clearly pointed out by W. Mattieu Williams. This defect makes itself apparent in certain astronomical observations, when the observer has to note the moment at which a star appears to touch the wire or wires stretched across the field of a telescope. The old way of doing this was to look at a clock as the star approaches the wire, count the beats of the clock, and then note at which beat or fraction of the beat the transit of the wire occurs. Despite the apparent simplicity of this operation there is no human being whose eye, ear, and internal nervous apparatus of perception and volition are sufficiently perfect to perform it accurately. None of us either sees, hears, or feels instantaneously. The sensation has to be transmitted from the external organ of sense to the nervous center, and the response has to be transmitted outward. These operations involve time. Nor is that all: they require a different length of time for different persons, different constitutions. Thus in the same observatory there may be three assistants. A, B, and C, and they are tested by making a number of corresponding observations. In every case it will be found that A is say a quarter of a second ahead of B, and B half a second ahead of C. What is to be done? If all erred alike—if all observers required just half a second to collect their sensations of sight and hearing, and to bring them to bear upon the same perception, then by setting the clock half a second ahead of the true time, the needed correction would be made. But, failing this, some personal standard of comparison must be taken, and the observers' rated to this standard like chronometers. This is done in observatories, and the result is called the "personal equation" of the individual observer. And not only has the personal equation of each observer to be determined on his entrance upon his duties, but it demands periodical revision, for it varies with age and constitutional conditions.

Use of the Balloon in Arctic Exploration.—In a paper read before the London Aeronautical Society, Mr. Brearey, its secretary, advocated the employment of balloons in polar exploration. Referrringto the last English polar expedition, Mr. Brearey said that, instead of a seventy days' journey to accomplish about seventy miles, at a fearful cost of life and suffering, consequent on having to drag over ice hummocks sleds containing provisions, the whole of the stores could have been conveyed over the heads of the explorers, and the men holding the ropes of this floating observatory would have been assisted by the upward tendency of the balloon. The question is, Would the daily consumption of stores compensate the leakage of gas? and its answer is found in Beaumont's history of the balloon as employed in the United States war of the rebellion. He writes that "the balloon when inflated can, unless in very windy weather, be very readily carried. Twenty-five or thirty men lay hold of cords attached to the ring and march along, allowing the machine to rise only sufficiently to clear any obstacle." He had frequently seen it carried thus without the least difficulty. As for the leakage of gas, by the use of proper varnish it might be so checked that at the end of a fortnight the balloon could make an ascent without being replenished. Remarks by various members of the Society followed the reading of the paper; they are briefly stated in the "Monthly Journal of Science," and are, on the whole, favorable to Mr. Brearey's views. Mr. Glaisher saw no reason why the balloon should not be made available in arctic exploration, and he hoped that, if there were another expedition, the balloon would be tried and the question settled. It would certainly, if used in connection with a sled, enable the explorers to travel much more rapidly than they can at present. Touching on the use of the balloon as an observatory, he said that, when he was only half a mile over London, he could see Margate and Brighton. This showed how much may be seen from a comparatively small elevation.

A Blood-sucking Squirrel.—Dr. Richard E. Kunze gives in "Science News" an entertaining account of a pair (male and female) of pet gray squirrels, one of which, the male, he detected in the act of sucking the other's blood. Having noticed that the female looked emaciated, and that in moving about she dragged a hind leg, Dr. Kunze made an examination, which resulted in the discovery of a circular hole in this leg directly over the hamstring muscles, extending through the entire thickness of the skin. The edges of this opening, or sore, which was of the diameter of a lead-pencil, looked smooth and blanched. Now, it could not be the result of a puncture or any other wound, because there was present neither inflammation nor discharge. It had the appearance of an artificial issue, was sensitive but not painful. For a time he was puzzled to account for the hole, but at last he caught her companion in the act of sucking her blood. The "vampire" was seen to bury his snout deeply in the fur in the direction of the sore. Soon the female squirrel, which had before been asleep, gave a sharp cry. "My suspicions," writes Dr. Kunze, "were soon confirmed, that he was actually sucking out the very life-substance of his mate. For several days a number of medical friends kept a sharp lookout on Foxie's unnatural conduct. At first we simply drove him away from his mate whenever he was intentionally too near the coveted spot. We now had to beat him off. In proportion as we resorted to such severe measures, Foxie became more cunning, and with an Argus-eye would watch his chance to act unobserved. Finally, he became much bolder in his onslaughts. He would seize the leg whenever he could get hold of it. I have seen him time and again place both hands on each side of the 'sore,' apparently gently pressing down the edges, just as a little kitten in nursing would keep up a pressure on the milk-ducts, and simultaneously suck with all his might."

Blindness and its Causes.—According to the last census returns there were, in the United Kingdom of Great Britain and Ireland, 31,159 blind persons, or one in 1,015 of the population. The proportions in different parts of the kingdom vary greatly, from one in 635 in Cornwall to one in 1,367 in Durham; the proportion being higher in agricultural than in urban districts. It is gratifying to learn that though the actual number of the blind increases, their proportion to the seeing population diminishes—a change which is probably due partly to the improvements in ophthalmic surgery, partly to the greater attention paid to the laws of hygiene. But that there is still room for much improvement in the latter respect is only too apparent from the imperfect returns of the causes of blindness made by the directors of a few schools for the blind. Thus the report of the York School shows that out of 82 pupils 36 lost their sight from purulent ophthalmia. And similar results are observed in countries on the European Continent. For instance, according to Marjolin, out of 208 pupils in the Paris Institution for the Blind, 80 became blind from this disease, and 18 from small-pox; so that one half lost their sight from preventable causes. In the institutions of Germany the loss of sight from purulent ophthalmia is stated to be about 30 per cent.

The impairment of eyesight by habitual protracted reading has been made a special subject of study by M. Javel, a French physician, who also proposes a method of reducing to a minimum the damage so caused. In the first place, reading requires an absolutely permanent application of eyesight, resulting in a permanent tension of the organ. Secondly, books are printed in black on a white ground; the eye is thus in presence of the most absolute contrast which can be imagined. The third peculiarity lies in the arrangement of the characters in horizontal lines, over which we run our eyes. If, during reading, we maintain a perfect immobility of the book and the head, the printed lines are applied successively to the same part of the retina, while the interspaces, more bright, also affect certain regions of the retina, always the same: the result is fatigue. Last and most important of all, in M. Javel's estimation, is the continual variation of the distance of the eye from the book. The accommodation of the eye to the page undergoes a distinct variation in proportion as the eye passes from the beginning to the end of each line; and this variation is all the greater in proportion to the nearness of the book to the eye, and the length of the line. In order to avoid these injurious effects, M. Javel advises frequent intermissions during reading. To reduce the contrast between the white of the paper and the black of the characters, M. Javel recommends the adoption of a slightly yellow tint of paper. His third suggestion is to give preference to small volumes which can be held in the hand, which obviates the necessity of the book being kept fixed in one place, and lessens the fatigue resulting from accidental images. Lastly, M. Javel advises the avoidance of too long lines, and therefore he prefers small volumes, and for the same reason those journals which are printed in narrow columns. Of course, every one knows that it is exceedingly injurious to read with insufficient light, or to use too small print.

An Insect Ragman.—A correspondent of "Hardwicke's Science Gossip" tells of a very curious discovery he made last summer at Bellosguardo near Florence, viz., a veritable insect ragman. Having noticed what he at first took to be a little nest of spiders' eggs blown along a window-sill, he was led to examine it more closely, and found it to be a rather untidy, fluffy ball, about the size of a large pea; further, that it was moving along of its own accord, stopping now and then for a second, and again resuming its journey. It was soon discovered that the ball of fluff was borne on the back of a little insect somewhat resembling the larva of the dermestes, and that the mass was composed of cobweb held on the creature's back by being twisted about in and out among the long hairs on the upper surface of the body. The insect was about one quarter of an inch in length, and bore on its head a pair of forceps about the size of those borne by the common earwig, but its purpose was very different, "for to my amazement," says the author, "I noticed that, each time the creature paused, it was to pick up, with these forceps, some dead ant or portion of a dead insect; and these fragments were picked up so deftly, and in so droll a way did the creature turn its head round and carefully arrange his treasure on his pack, that I was forcibly reminded of the chiffonniers in France and Italy, with their hook and their basket, and of the 'ole clo'' and his pack in England. . . . For more than two days I kept it in a small glass-lidded box, supplied it with 'ole clo,' and watched it constantly collecting and packing; but I never saw it feed, and one morning I found that a large ant I had supposed to be dead had attacked and eaten the creature, scattering the fluffy pack and its contents all over the box." Some weeks after this the author received a note from a friend at Vevey, who from the description recognized the "chiffonnier," two of which, she says, "came toward me, on the table in the garden where I was seated reading, collecting and packing as you have described." From a friend at Bellosguardo he also, on his return to England, received an account of one she had found, and of which she thus writes: "I had half a mind to send you one of those scavenger or 'ole clo'' insects; but could not arrange anything that would insure its arriving alive. The pack on his back is much less choice than the others, consisting of parts of the bodies of dead flies, spiders' cobwebs, etc., while he himself is much smaller. I feel quite sure it is his food he collects, because the first night I put him under a tumbler he ate the wings of his fly, the only ornamental article in his collection. He is exceedingly fond of sugar—has eaten, I am sure, twice his weight—and has just added two small dead ants to his load, under which he staggers visibly. His pack is held on by long, projecting hairs, and likewise secured and strengthened by cobwebs."