Popular Science Monthly/Volume 15/June 1879/Popular Miscellany
The National Academy of Sciences.—Professor O. C. Marsh, who, after the death of Professor Joseph Henry, became acting President of the National Academy of Sciences, in his address at the annual meeting of that body, held in Washington, April 15th, presented a detailed statement of the action of the Academy with regard to the reorganization of the survey of the Territories. He also submitted a report of the progress which has been made in putting into execution Professor Newcomb's plan for determining the distance of the sun by measuring the velocity of light. Professor Marsh justly congratulates the Academy upon the unanimity with which the members adopted the scheme for reorganizing the surveys, and on its embodiment without change in a law of Congress. The Academy, in all its deliberations upon this important matter, was strictly unpartisan, and acted without respect of persons. Whether the scheme which now goes into execution will lead to better results than the old plan of many independent surveys, Professor Marsh leaves to the historian to decide. For the purpose of carrying out Professor Newcomb's plan of determining the sun's distance, the sum of five thousand dollars has been appropriated by Congress; and the work of constructing the necessary apparatus will be commenced as soon as the appropriation is available. It is hoped by those who proposed this plan that the experiments will lead to a more accurate determination of the distance of the sun than can be reached by any other method known to astronomers.
The Growth of a Continent.—The history of the growth of the European Continent, as recounted by Professor Geikie, gives an instructive illustration of the relations of geology to geography. The earliest European land, he says, appears to have existed in the north and northwest, comprising Scandinavia, Finland, and the northwest of the British area, and to have extended thence through boreal and arctic latitudes into North America. Of the height and mass of this primeval land some idea may be formed by considering the enormous bulk of the material derived from its disintegration. In the Silurian formations of the British Islands alone there is a mass of rock, worn from the land, which would form a mountain chain extending from Marseilles to the North Cape (1,800 miles), with a mean breadth of over thirty-three miles and an average height of 16,000 feet. The Silurian sea which spread across most of central Europe into Asia suffered great disturbance in some regions toward the close of the Silurian period. It was ridged up into land inclosing vast inland basins, the areas of some of which are still traceable across the British Islands to Scandinavia and the west of Russia. An interesting series of geographical changes can be traced, during which the lakes of the Old Red Sandstone were effaced, the sea that gradually overspread most of Europe was finally silted up, and the lagoons and marshes came to be densely crowded with the vegetation to which we owe our coal-seams. Later terrestrial movements led to the formation of a series of bitter lakes across the heart of Europe, like those now existing in the southeast of Russia. Successive depressions and elevations brought the open sea again and again across the continent, and gave rise to the accumulation of the rocks of which most of the present surface consists. In these movements the growth of the Alps and other dominant lines of elevation can be more or less distinctly traced. It was at the close of the Eocene period, however, that the great disturbances took place to which the European mountains chiefly owe their present dimensions. In the Alps we see how these movements led to the crumpling up and inversion of vast piles of solid rock, not older in geological position than the soft clay which underlies London. Considerable additional upheaval in Miocene times affected the Alpine ridges, while, in still later ages, the Italian Peninsula was broadened by the uprise of its sub-Apennine ranges. The proofs of successive periods of volcanic activity during this long series of geographical revolutions are many and varied. So, too, is the evidence for the appearance and disappearance of successive floras and faunas, each no doubt seeming at the time of its existence to possess the same aspect of antiquity and prospect of endurance which we naturally associate with those of our own time. The law of progress has been dominant among plants and animals, and not less upon the surface of the planet which they inhabit. It is the province of the biologist to trace the one series of changes, of the geologist to investigate the other. The geographer gathers from both the data which enable him to connect the present aspects of nature with those out of which they have arisen.
Storms and Neuralgia.—At the April meeting of the National Academy of Sciences, Dr. S. Weir Mitchell read a paper on "The Relation of Neuralgic Pain to Storms and the Earth's Magnetism." The interesting observations here recorded were made by Dr. Mitchell in conjunction with Captain Catlin, of the United States Army, who lost a leg during the war, and who, since that time, has suffered from traumatic neuralgia, sometimes in the heel, but more frequently in the toes, of the lost foot. The hourly observations cover a period of five years. For the first quarters of these five years there were 2,471 hours of pain; for the second quarters, 2,102 hours; for the third quarters, 2,056 hours; and for the last quarters, 2,221 hours. The greatest number of hours of pain is in January, February, and March; and the least in the third quarters, July, August, and September. During these five years, while the sun was south of the equator, there were 4,692 hours of pain, against 4,158 hours while it was north of the equator; and the greatest amount of pain was in the quarters beginning with the winter solstice, and the least was in those beginning with the summer solstice. The average duration of the attacks for the first quarters was 22 hours, and for the third quarters only 17·9 hours. By taking the four years ending January 1, 1879, it is found that, of the 537 storms charted by the Signal Bureau, 298 belong to the two winter quarters, against 289 for the summer quarters. Hence we have the ratio of the number of storms of the winter quarters and summer quarters corresponding to the ratio of the amounts of neuralgia for these respective periods, and the ratio of average duration of each attack for the same time corresponds closely with the ratio of the respective total amounts of neuralgia for the same periods. The average distance of the storm-center at the beginning of the neuralgia attacks was 680 miles. Storms coming from the Pacific coast are felt farthest off, while storms along the Atlantic coast are associated with milder forms of neuralgia, and are not felt until the storm-center is nearer. Rain is not essential in the production of neuralgia. It was found that the severest neuralgic attacks of the year were those accompanying the first snows of November and December. Every storm, as it sweeps across the continent, consists of a vast rain area, at the center of which is a moving space of greatest barometric depression, known as the storm-center, along which the storm moves like a bead on a thread. The rain usually precedes this by 550 to 600 miles; but before and around the rain lies a belt which may be called the neuralgic margin of the storm, and which precedes the rain about 150 miles. This fact is very deceptive, because the sufferer may be on the far edge of the storm-basin of barometric depression, and see nothing of the rain, yet have pain due to the storm.
Physiological Action of Aconite.—From certain experimental inquiries into the physiological action of aconite and its alkaloid, aconitia. Dr. G. H. Mackenzie concludes that these drugs act primarily on the respiration by their influence on the respiratory center and peripheral sensory branches of the vagus nerve. They have no direct action on the heart, and only affect that organ secondarily through the medium of the lungs. Their action on the nervous system consists in firstly irritating and secondly paralyzing the peripheral sensory nerves and posterior roots of the spinal nerves. They have no direct action on the brain or the vaso-motor nerves. They increase the irritability of the peripheral motor nerves, and of the motor columns of the cord. They do not induce muscular paralysis, but, on the contrary, increase the irritability of voluntary muscle. They induce convulsions mainly through their augmenting the irritability of the anterior column of the cord, the motor nerves, and muscles. They firstly increase and secondly diminish temperature. Death ensues from asphyxia and respiratory collapse.
Curiosities of Nervousness.—An interesting book might be made out of the curiosities of nervousness from a contemporary standpoint. The elder Disraeli has somewhere a chapter on the subject; but, if our memory serves us correctly, his instances trench rather upon the hysterical conditions, the monomanias, the wild fanciful delusions of the disordered imagination, than upon the prosaic features of the distemper. He instances men who could not bear the sight of old women, and fainted dead away if a grandmother showed herself; others who, if they heard a rat in the wall, took it for a ghost and got up and prayed fervently; and such things. The present age furnishes more rational imaginings, born of the daily papers, emphasized by indigestion, and riveted by the surprising eloquence of the diurnal quidnuncs. For instance, there are plenty of people living at this moment who would warmly refuse to get into bed before looking under it to make sure that no man lay there. There are others who pass the night in constant fear of fire; who, before they withdraw to their bedchambers, carefully rake out every fireplace in the house, turn off the gas, inspect every room, knock on the servants' doors and inquire through the key-holes if their candles are out; and after all this bother go to bed and lie awake until the dawn with their bedroom doors ajar, sniffing at imaginary fumes of burning, and ready to spring out and go raving mad should anything like a cry be raised—for these people never make any serious provision against fire should fire come. There are others, again, who will lie night after night in expectation of burglars. A distant footfall will court them to the window, where, cautiously pulling aside the blind by the breadth of a nose (giving scope to one eye), they will peer into the gloom and mistake some shadow for the figure of a man (wrapped in an overcoat and with a horse-pistol in every pocket), intent upon the particular window whence he is being watched. Others will be kept awake by the song of the wind about the casement, or in the empty rooms around, confounding these natural sounds with the murmur of human voices in the pantry, or on the landing just outside.
These are some of the hundred night fears beyond an ordinary imagination to express. But there are daylight fears as numerous, if not always so agonizing. What words can convey the horror felt by a certain kind of nervous people who, making a journey on a railway, are suddenly brought to a stand in a tunnel? Nothing can comfort them. Their heads shoot through the windows, their cries lacerate the gloom, and the reassuring shouts of the guard only aggravate their fright and provoke fresh yells for immediate release. Or take the mental condition of another kind of nervous persons at sea. Every roll of the vessel means imminent death. The carrying away of a water-cask, the momentary stoppage of the engines, the cry of a man on the lookout, the escape of a sail from the gaskets that confine it to the yard, and its consequent bellowing upon the gale, the abrupt shipping of a sea, nay, the tumbling of a steward down a ladder, or the fall and smash of a few plates from the leaning saloon table, will strike an indescribable horror, and lead to no end of convulsive clingings and mumblings of prayer. Indeed, it would be possible to fill every page in this journal with a catalogue of the imaginative afflictions under which nervous people labor. Old Doctor Johnson, going back to touch an omitted post, typifies a host of numerous disorders which need not be mistaken for superstitions, and which assume a vast number of shapes among us in these days. Take a pavement full of people with a ladder across it from the house-top to the curbstone. How many of the passengers will wade into the mud of the road to save themselves from passing under that ladder? The proportion of the nervous people in the world will be happily indicated by such an example. Of every hundred persons, we question if ten would, without hesitation, pass under that ladder. When a man refuses to make his will, because he fears that by doing so he will be hastening his death, are we not to attribute his cowardice to the nerves? It is a mere convenient apology to call such misgivings superstitions. No one would hope to cure a priest's faith in a winking Madonna by a course of quinine; and superstitions of the real sort are assuredly not to be corrected by medical treatment. But our latter-day nerves are to be dealt with, and a good many uncomfortable horrors taken out of our minds, by the judicious doctor.—"Mayfair."
A Botanical Usurper.—One of the most curious instances on record of the invasion of a country by a plant of foreign origin, and the extermination by it of indigenous species, is seen in the history of the mango tree in the island of Jamaica, as recounted by Sir Joseph Hooker. It reminds us of the accounts of captured tribes which after being carried into their conquerors' country have so increased and multiplied as eventually to dispossess and supplant their captors. In 1782 Admiral Rodney captured a French ship bound for San Domingo from Bourbon, with living plants of the cinnamon, jackfruit, and mango, sent to the Botanic Garden of the former island by that of the latter. The prizes were presented by the Admiral to the Jamaica Botanic Garden. There the cinnamon was carefully fostered, but proved to be difficult of culture in the island; while the mango, which was neglected, became in eleven years as common as the orange, spreading over lowlands and mountains from the sea-level to 5,000 feet above it. On the abolition of slavery immense tracts of land, especially coffee plantations, relapsed to a state of nature, and, the mango being a favorite fruit with the blacks, its stones were flung about everywhere, giving rise to groves along the roadsides and around the settlements; and the fruit of these again, rolling down hill, gave rise to forests in the valleys. The effect of this spread of the mango, Sir Joseph Hooker adds, has been to cover hundreds of thousands of acres, and to ameliorate the climate of what were dry and barren districts by producing moisture and shade, and by retaining the rainfalls that had previously evaporated; all this, besides affording food for several months of the year to both negroes and horses.
Explorations in Central Africa.—Two French travelers, M. Savargnan de Brazza and Dr. Ballay, have returned to Paris after a three years' exploration of the Ogowé (or Ogobai) River. In August, 1875, the travelers left Lambarene, the extreme limit of the European factories, and, escorted by twelve Laptots, or native African soldiers of the French colony of Senegal, explored the river to its sources. One result of the expedition is to prove that the Ogowé does not rise in an interior lake. The river may be divided into three nearly equal parts—the upper, the middle, and the lower. The middle follows an almost straight east and west course just south of the equator; the two others incline about a degree and a half toward the south. The first halt was made at Lopé, a large village on the upper Ogowé. M. de Brazza penetrated into the country of those noble cannibals, the Fans, with whom he entered into friendly relations, and succeeded in reaching Dumé, a position considerably advanced on the upper river. He suffered seriously in this journey, and on his return had to let his companions advance to Dumé without him; he was only able to rejoin them in April, 1877. Through great hardships and dangers they made their way to the Pubara Fall, above which the Ogowé becomes an inconsiderable stream.
After a few days' rest here, the explorers left the basin of the Ogowé in March, 1878, to penetrate still farther into the interior. They traversed successively the territories of the Ondumbo, the Umbeté, and the Bateké, suffering greatly on the way from both hunger and thirst, for the country was devastated by famine. A stream running east, the N'Gambo, led the explorers to an important river, the Alima, 500 feet wide and sixteen feet deep, apparently an affluent of the Congo. In attempting to descend the Alima they had to run the gantlet between banks lined with hostile savages. They quitted the river and marched northward, crossing many watercourses flowing eastward. They suffered so much from hunger that the expedition had to be divided, Dr. Ballay and one of the attendants being sent back to the Ogowé. M. de Brazza went some distance farther northward, when hunger and suffering compelled him also to retreat, and he rejoined his comrade in September. On November 30th the whole party reached the French settlement at the Gaboon.
From Corisco Bay, on the west coast of Africa, and a little north of the mouth of the Gaboon, comes intelligence of certain important explorations made by Hugo de Koppenfels, who reports that he ascended the Muni, the Noya, the Balinji, and the Tambuni to the first falls. In the Crystal Mountains he fell in with tribes absolutely unknown up to the present, or who at least had not been seen by whites with rare exceptions—the Etemo, the Manga, the Otonto, and the Toko. These people are described as very inoffensive; they regarded their white visitor as a curious animal, and had a certain fear of him. When he asked them to accompany him into the interior they agreed readily. They are frightfully poor, being obliged to give up planting on account of the ravages of elephants and gorillas, which are very numerous and daring. Not a single night passed, the traveler states, that he did not hear those animals ravaging around the villages, which are mostly very large. As soon as the animals are known to be near, the whole village is on foot endeavoring to frighten them away by shouting. In these nocturnal expeditions, in which the explorer took part, he noticed that the head man of the village addressed a speech to the elephants, and that in this speech his own name was pronounced. He was told that the elephants were threatened to be handed over to him, and that, if they did not fly at once, they would be visited on the morrow, and the white man would kill them. If the elephant seizes a plant with its trunk, the people immediately raise a dreadful, plaintive howling, and the principal orator addresses, in a lamentable voice, supplications to the enormous brute.
The Animal "Outing."—That the change of scene and air secured by an annual "outing" is beneficial to health can not be doubted. The relief afforded counts for much, the opening up of new sources of energy counts for more, in the sum of advantages gained. Meanwhile, not only will the profit be small, but the result questionable, unless the relief and the sense of freshness are shared by mind and body alike. In a word, perfect absence of worry is essential to the full enjoyment and restorative action of the holiday. This is just what the majority of persons, particularly the heads of families, forget, for themselves and those around them. A jaded mind needs rest quite as much as a weary body, and neither the one nor the other can obtain the sort of rest which is essential to a complete renewal of strength without the awakening of new interests. The simple cessation of work may in some few instances give relief, but much more than this is necessary for the recovery of health and renewal of energy when mind and body are exhausted by long-continued or monotonous toil, or domestic duty. It follows that, in the choice of a locality and in the manner of conducting the trip, the inclination should be consulted not less than general convenience. It is too much the practice to make a toil of a pleasure, and create occasions of annoyance in the course of the annual holiday. Everything should be planned to leave the mind free as regards the obligations of home duty, and enable it to share the advantages of the change bestowed on the body. There is plenty of thought for the physical part of man's nature; it may not be unreasonable to put in a plea for the consideration of his needs as a being endowed with a mental part, which is apt to be overmuch burdened with responsibility and harassed by many cares. The annual outing will be incomparably more enjoyable, and productive of lasting benefit, if these needs of the mind are considered, instead of being systematically overlooked. People go away anxious, and return to mourn over the smallness of the benefit they have received. They took their worries with them, and might almost as well have staid at home.—Lancet.
What is a Poison?—Under the fanciful title of "The Keys of Death," we find in the "Monthly Journal of Science" a very interesting article on the subject of poisons. The author asks, in the first place, what is a poison, but science, he holds, is not yet qualified to give an answer. Certain physiologists have concluded that whatever is poisonous in large doses must also be poisonous in the minutest. But it is easy to give instances where, if the reagents employed are less in proportion, or weaker than the required standard, we obtain, not a smaller quantity of the product sought for, but a substance totally different. Oxygen is a case in point: diluted, it sustains life; pure, it destroys it. So with sulphuric acid. Mixed largely with water, it is a refreshing, tonic beverage; in the concentrated state it destroys all parts of the system which it touches. Again, a definition of poisons has been based on the fact that while certain articles of food undergo decomposition in the stomach, poisons do not. Then water is a poison, for it does not suffer decomposition in the system.
But, turning aside from these definitions, we find included under the general name of "poisons" two very different classes of bodies, viz., "germs" which, when absorbed by an animal, bring on such diseases as rabies, small-pox, cholera, etc.—in short, the zymotic diseases; and, in the second place, the true poisons, such as arsenic, strychnine, aconitine, etc. These latter substances are well-defined chemical individuals. When introduced into the system they set up morbid action almost immediately, and if the dose be sufficient the symptoms go on increasing in violence till death ensues. A characteristic feature is that their noxious power may be decreased or even extinguished by dilution.
The other class, however, the ferments, are not definite chemical principles, capable of being isolated, of entering into combination with other bodies, and of being separated again; they are, so far as we know, living organisms of low type.
The immunity of certain animals from the action of poisons which are fatal to others is remarkable. This difference of susceptibility often exists between individuals of the same species, being developed in some cases by natural selection, in others by habituation. The author of the paper in the "Journal of Science" gives the following list of caterpillars which feed on poisonous plants: Gonopteriyx rhamni, on Rhamnus catharticus; Thats polyxena, on species of Aristolochia; Danais archippus and chrysippus, upon various Asclepiads; Deihphila galii, Nicea, and Euphorbiæ, on species of Euphorbia; Chærocampa nerii, on the oleander; Sphinx polia cappa, on staves-acre; Heliothisa armigera, on tobacco; and Chrysoptera moneta, on monk's-hood.
A New Electric Pen.—In the "Monde de la Science" is a description of an improved electric pen, much cheaper than Edison's, and not so fatiguing to the operator; the inventor would appear to be an Englishman, Wentworth L. Scott. The pen consists of an open glass tube drawn out to a point at one end, where there is a minute orifice. Within the tube is a copper wire, to which a fine platinum point is soldered toward the lower end of the pen. This copper wire is held in the middle of the tube by means of a cork stopper at the larger end (the upper end of the pen). The point of platinum should just reach the tip of the pen. To work the instrument the copper wire is connected with one of the poles of a Ruhmkorff coil. The other pole is connected with a zinc plate, on which the paper is to be laid. The circuit is now closed, and so soon as the current flows it causes the interrupter of the Ruhmkorff coil to vibrate. The pen is then made to move over the paper, as in writing, care being taken only to touch the glass tube, for fear of electric shocks, and electric sparks are seen to pass with great rapidity between the point of the pen and the paper. On holding up the paper between the eye and the light, the track of the pen is seen to consist of minute perforations, like those produced by Edison's electric pen. The instrument is as light as a common pen. The cost of the whole apparatus is trifling, about eighteen francs.
Alum as an Adulterant of Baking-Powders.—Dr. Henry A. Mott, Jr., employed as chemist for the Indian Department, having made analyses of different baking-powders, publishes in the "Scientific American" as the result of his investigations the statement that at least fifty per cent, of the many baking-powders examined by him were grossly adulterated. Dr. Mott found that the injurious powders are composed of alum and bicarbonate of soda, oftentimes containing also terra alba, insoluble phosphate of lime, etc. The best powders are composed of bitartrate of potash (cream of tartar), tartaric acid, carbonate of ammonia, and bicarbonate of soda, held together by a little starch to prevent decomposition. The injurious effects of alum on the digestive organs have been pointed out by eminent chemists and physicians: it produces dyspepsia, constipation, vomiting, griping; it is a powerful astringent, acting chemically on the tissues. Says Dumas, the French chemist: "It is to be feared that this salt (alum) exerts a deadly action by its daily introduction into the stomach, especially in persons of weak constitution." Liebig condemns the use of alum in bread-making on this ground among others, that it combines with the soluble phosphates, forming insoluble salts, and thus the phosphorus of the grain is lost to the system. Dr. Mott's paper exhibits as follows the results of the analysis of four brands of baking-powder:
DOOLEY'S STANDARD BAKING-POWDER.
| Burnt alum | 26·45 | per cent. |
| Bicarbonate of soda | 24·17 | "" |
| Sesquicarbonate of ammonia | 2·31 | "" |
| Cream of tartar | None | |
| Starch | 47·07 | "" |
| 100·00 |
PATAPSCO BAKING-POWDER.
| Burnt alum | 20·03 | percent. |
| Bicarbonate of soda | 22·80 | "" |
| Cream of tartar | None | |
| Starch | 57·17 | "" |
| 100·00 |
CHARM BAKING-POWDER.
| Burnt alum | 30·06 | per cent. |
| Bicarbonate of soda | 31·82 | "" |
| Cream of tartar | None | |
| Starch | 38·12 | "" |
| 100·00 |
BAKING-POWDER MANUFACTURED BY C. E. ANDREWS & CO., MILWAUKEE, WIS.
| Burnt alum | 22·53 | per cent. |
| Bicarbonate of soda | 21·79 | "" |
| Cream of tartar | None | |
| Starch | 55·68 | "" |
| 100·00 |
Adulteration of Food and Drugs.—Some astounding facts with regard to the adulteration of articles of food and medicine are brought together by the "Medical and Surgical Reporter,"' being taken from various medical and pharmaceutical periodicals. Thus we are told that in New England several mills are engaged in grinding white stone into powder for purposes of adulteration, three grades of powder being ground at some of the mills, viz., a soda grade, a sugar grade, and a flour grade. A Boston chemist has found seventy-five per cent, of terra alba in a sample of cream-tartar; and most of our confectionery contains thirty-three per cent, or more of this substance. These and many other adulterations of materials used in the preparation of food have been pointed out in "The Sanitarian." The adulteration of drugs is practiced to such an extent that "in some localities a conscientious pharmacist is hardly able to earn a livelihood, owing to the mean and dishonest competition which surrounds him." "Salieine," writes a physician in a Louisville medical journal, "is heavily adulterated by mixing it with cinchonidia sulphate." Again, the editor of "The Pharmacist" sought in vain among the druggists of Chicago for black sulphuret of antimony. He obtained what purported to be that substance at seven wholesale drug-houses; but not a trace of antimony was to be found in any of the samples! Analysis showed it to be in most cases simply marble-dust blackened with soot.
Pinto's Trip across Southern Africa.—A telegram received at Lisbon, on March 11th, announced the arrival of Major Serpa Pinto on the eastern coast of Africa, after having traversed the continent from Benguela on the west coast. We take from "Das Ausland" the following account of Major Pinto's memorable journey: On November 12, 1877, he set out from Benguela, in Lower Guinea (about latitude 13° south), and on March 8, 1878, entered the negro kingdom of Bihé, where he had his first fight with the natives. He devoted himself particularly to the exploration of the upper and middle Zambesi, that grand stream which, lying some ten degrees of latitude south of the Congo, like that river traverses almost the entire breadth of the African Continent. If it is the purpose of Portugal to found in equatorial Africa another Brazil, the most accurate knowledge of the course of the Zambesi must be of the utmost importance to her. Portugal controls the coast on both sides, the western and the eastern, in equatorial South Africa, and, if she succeeds in establishing communication between these two coasts by means of the Zambesi, the new colonial empire would be a fact. This project is favored by the wealth of gold found in the lower Zambesi regions, and it is surely no mere accident that latterly the Government has been making large concessions to English and Portuguese companies. Incidentally Major Pinto appears to have revealed the mystery of the Cubango, a stream whose sources are not very distant from those of the Zambesi, but which soon takes a north and south direction. Only the upper course of this stream was hitherto known to Europeans. It was supposed that farther down it turned to the west and flowed into the Atlantic as the Owambo or Cunene. Pinto has now probably made the discovery that the Cubango is a tributary of the Zambesi. However this may be, our knowledge of the interior of Africa has been considerably enlarged by Pinto's journey.
On reaching the Transvaal Territory the explorer sent the following dispatch to the King of Portugal: "I am now six days' journey from the Indian Ocean, and on the point of completing my march across Africa from the west coast. I have struggled against hunger and thirst, wild beasts, savages, floods, and drought, and have happily surmounted all these obstacles. My records are safe, and consist of twenty geographical charts, three volumes of important coördinates, meteorological notes, three volumes of sketches, and a voluminous journal. I have lost several men. Complete study of the upper Zambesi, sixty-two cataracts and rapids. Plan of the cataracts. The natives fierce; unceasing wars. The secret of the Cubango.Serpa Pinto."
Strength of Hard and Soft Steel.—It has hitherto been supposed that a soft bar of steel can longer resist the disintegrating action of strains and shocks than a hard one, but experiments made by W. Metcalf, of Pittsburg, appear to prove the contrary to be the fact. His attention was first called to this matter by the constant breaking of steam-hammer piston-rods. Made of ordinary steel, they lasted but six months, an iron rod lasting but half as long. Then lower and lower steels were tried, and broke in about five months. In an emergency, a rod of comparatively high steel was employed, and this, which it was supposed could not serve for more than a week or two, held out for more than two years. This result led Mr. Metcalf to investigate the whole subject systematically, and a lot of small steel connecting-rods were tested in a special machine. The test required was, that a machine should run 412 hours at a rate of 1,200 revolutions per minute, unloaded, before the connecting-rod broke. These rods were unforged in the middle, and consisted of a piece of round bar with a head welded on each end. "The mode of rupture was," says Mr. Metcalf, "as a rule, the same in all cases; the rod heated at the middle, where the vibrations met, as they were imparted by rotary motion at one end, and by reciprocating motion at the other, and by alternating strains of compression and extension. In some cases the rod became slightly red-hot at the middle before rupture. After heating, the next thing observed was the raising or loosening of the surface scale of the middle. Soon after this, rupture began, first at the surface and gradually extending to the center. The breaking was gradual in every case, no piece breaking suddenly, even of the highest steel. The first trial was with ·53 carbon steel: mean time of six trials, 2 hours 918 minutes. Second trial, ·65 carbon steel: mean time of six trials, 2 hours 5712 minutes. Third trial, ·85 carbon steel: mean time of three trials, 9 hours 45 minutes, and the trials were stopped." A set of twelve connecting-rods, made from special ingots, was then prepared. These were tested with the following results:
The ·30 C ran 1 hour 21 minutes, heated and bent before breaking.
The ·49 ran 1 hour 28 minutes.
The ·53 ran 4 hours 57 minutes, broke without heating.
The ·65 ran 3 hours 50 minutes, broke at weld where imperfect.
The ·80 ran 5 hours 40 minutes.
The ·84 ran 18 hours.
·87 C broke in weld near the end.
·96 C ran 4 hours 55 minutes, and the machine broke down.
The whole twelve were not tested, because the machine was needed for other works, and, when Mr. Metcalf returned to complete the experiment, it was discovered that the foreman of the shop had picked up the unbroken specimens, put them into machines, and sent them off. Enough was done, however, to show that the maximum of strength to resist vibration was not found among the ductile steels. Mr. Metcalf gives some other data concerning the performance of steel suspension-rods in a bridge that corroborate his views, which are practically novel.