Popular Science Monthly/Volume 31/July 1887/Popular Miscellany

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Popular Science Monthly Volume 31 July 1887  (1887) 
Popular Miscellany
 

POPULAR MISCELLANY.

The Glacial Lake and Island of Cincinnati. — The city of Cincinnati occupies, as Professor Joseph F. James remarks, one of the most interesting geological positions on the North American Continent. The strata of its hills are almost wholly composed of Lower Silurian fossils, in nearly perfect preservation, packed as closely as they can be stowed together. Besides this, it furnishes most interesting marks of the conditions which prevailed in the region in glacial and pre-glacial times. After the close of the glacial period, in the presence of the debris left by the ice-sheet, blocking up in places the beds of the former streams, new channels had to be sought by the water. Many streams were compelled to form entirely new channels, but others had to carve + 2 4

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��new courses only in places here and there. The Ohio River seems to have been in the latter category, for in many places its valley is too wide and too deep to have been exca- vated by the volume of water now flowing at ordinary stages. In fact, there seems little doubt that tho Ohio flows in a channel which was cut long previous to the glacial period. This old channel has been largely filled up, and the river now flows from thirty-five to forty feet above its ancient bed. This seems to be proved by the dis- covery, at that depth below the present sur- face of the ground, of an extensive bed of carbonaceous material consisting of stumps of trees, leaves, seeds, and other vegetable remains. Several facts seem to point to the conclusion that on and near the site of the city was once spread out a sheet of water that assumed almost the aspect of a lake. The outlet of this sheet was not like the present course of the river, past the mouth of Mill Creek, but up what is now Mill Creek Val- ley on one side, and up the Little Miami Valley and an ancient channel between Red Bank and Plainville on the other side, of what then formed an island now occupied by a part of the hill suburbs of Cincinnati. These ancient channels extended northward on the east and west of the island, and united near where Ludlow Grove now is, and thence together held their way north- ward to Ilamilton; there they turned to the west and south, and reached the Ohio River Valley as it is now, somewhere near Law- renceburg, Indiana, by following the course now used by the Big Miami. In those days a barrier of land stretched from Price Hill across to the Kentucky side. It is supposed that during the glacial period the end of an immense glacier extended south as far as the Ohio River, and at Cincinnati so com- pletely blocked the channel as to compel the river to seek another course. But at the close of the ice age, and when the glacier had melted, the river attempted to return to its former channels. Finding, however, its old bed filled with sand and gravel, the debris of the retired ice-field, and finding, perhaps, that the former im- passable barrier had lost some of its height, it beat against it, gradually wore it away, and cut for itself a new channel from the mouth of Mill Creek to Lawrenceburg.

��Natural Gas at Pittsburg. From &

lecture delivered at the Franklin Institute, December 18, 1886, by Mr. Charles A. Ash- burner, Geologist in charge of the State Geo- logical Survey, it appears that there are now six natural gas companies in Pittsburg, managing 107 wells, and supplying the gas through more than 500 miles of pipe, of which 232 miles arc in the city proper. The total area of pipe leading into Pitts- burg is given as 1,346,608 square inches, and the total capacity of the mines is esti- mated at more than 250,000,000 cubic feet of gas per day. One company supplies more than 400 manufactories and 7,000 dwellings with all the fuel consumed in them. The composition of the gas varies greatly, but it may be generally described as a mixture of hydrogen, nitrogen, and marsh gas, with occasionally higher carbon compounds. A thousand cubic feet of gas is calculated to equal in heating capacity fifty-five pounds of coal. The use of gas for domestic pur- poses has been facilitated by the inventions of Mr. Westinghouse, among which are a device for preventing leaks and a pressure- regulator. The gas is furnished to the con- sumer on a yearly contract with a company for supply at certain rates and costs, to heat and light a house containing twelve rooms for from $70 to $90 a year. With it, every room may be kept at a temperature not varying two degrees, regardless of the condition of the outside temperature, or of pressure on the mains. While the lecturer admitted that the source of natural gas is capable of exhaustion, he did not think there was any imminent danger of such a calamity.

Origin of the " Second Growth " in Woods. The origin of the second growth that springs up after a forest has been cleared away, which is usually different in kind from the previous growth, has given rise to one of the problems that have never been solved. Perhaps the most frequently suggested explanation is that it springs up from seeds that have lain dormant in the ground for centuries ; but aside from its being hard to conceive of seeds preserving their vitality for so long a time under the conditions to which they must be exposed, this supposition does not account for the

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��origin of the seeds. Dr. Clevenger, of Chi- cago, thinks that the soil has been substan- tially exhausted of the constituents favor- able to the growth of the original timber, and has become more suitable for the sup- port of other or complementary sorts ; but as against this, evidence of the supposed exhaustion seldom exists, and the origin of the seeds is still unaccounted for. Mr. John T. Campbell, of Rockville, Indiana, a practical woodsman, supposes that while most forest-seeds are not ready to grow in the leaf-fall of the parent tree, other seeds and nuts are transported for long distances and in great numbers by crows, woodpeckers, 6quirrels, etc., and that these are the seeds from which the new growth arises. This theory must depend largely upon whether nuts are actually transported in such num- bers as it requires, by the agencies men- tioned. Mr. Campbell adduces an incident that occurred under his own observations, in which, if not the identical thing, some- thing very like it was done.

Work and Play in Instruction. School Superintendent B. A. Hinsdale, of Cleve- land, Ohio, remarks, upon a precept laid down by President Eliot in one of his ad- dresses that " a subject is good for a child precisely in proportion to his liking for it, or, in other words, to his taste and capacity for it," that a capital distinction should be made between work and play. The object of education is to learn to do work. This fact should not be lost sight of, even though the road to the end be made to lead, at times, a little way through play. " The child has a spontaneous nature that should be harnessed to studies and to the whole work of life. Automatic attention is that state of the mind in which its energy is given to a thing from some native affinity or attraction ; volitional attention, that state in which its energy is given by act of choice. The development of volitional attention is one of the highest results of discipline. Now, in training the child the spontaneous attention must be rallied to the support of the volitional, which is weak or does not at first exist at all, but as time goes on the volitional attention should grow and become more and more independent of the sponta- neous. Humor has been likened to the

��lever, by means of which we raise great weights with a small force. Love and en- thusiasm are also powerful motives. There is a large suggestion for the teacher in the fact that a little boy who has complained bitterly of the wearisomeness of walking will, when put astride of his grandfather's cane, and told that it is a horse, scamper away all forgetful of his previous com- plaints. But somewhat of life consists of walking when one is weary, and no boy is fitted for life who can not walk. The child should indeed be led to the hard by the way of the easy, but the man has no real train- ing or character who can not, on due occa- sion, collect his powers to do a multitude of things that he considers hard and disagree- able. The spontaneous powers keep us alive in infancy, and death comes when they wholly fail us, but the highest end of edu- cation is the fullest development of the judgment, the moral sense, and the will. Hitch the spontaneous forces to your wagon by all means, but, if you have no other horses, you should not be surprised to find that you drive a balky team. ... It is not true that nothing is good for training that is not hard, but it is true that no training is complete that does not involve much severe and vigorous labor. It is not true that men- tal exercise is useful only when it is repul- sive and distasteful, needing a dead-lift of the will, but it is true that a good many of such ' lifts ' have to be made, and the child must be got ready for the lifting. ... In a word, my whole contention is that the child must be brought, progressively, of course, to measure his full powers with the labors and. difficulties of life."

How the Structure of Rocks is deter- mined. Mr. George F. Becker, in a paper pertinent to some differences of opinion between himself and Messrs. Hague and Iddings, of the United States Geological Survey, concerning the rocks of the Washoe district, remarks that, given the chemical constitution of an eruptive magma, the min- eralogical results are dependent solely on the physical conditions to which it is sub- jected. It is not a question, therefore, whether, if similar magmas are subjected at different times to similar temperatures and pressures, similar mineralogical results

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��will ensue, but whether at different geo- logical eras the physical conditions attend- ing the cooling of eruptive masses have been substantially identical. That this has sometimes been the case will scarcely be denied. The problem with which geologists have to deal, however, is not precisely that just stated, for, since the earlier formations have been deeply eroded, while the degrada- tion of comparatively recent rocks is, as a rule, correspondingly small, upper portions of more recent eruptions have to be com- pared with lower portions of more ancient eruptions. The lithological problem is, therefore, greatly complicated. The main purpose of lithology being, as the author believes, to trace the physical conditions through which a mass of readily ascertain- able chemical composition has passed, in the present state of ignorance concerning the effects of temperatures and pressures, the most rational method is to study and record every peculiarity of every occur- rence and every perceptible difference be- tween rocks. . . . Rocks can, of course, never be classified with the sharpness of minerals. Rocks are essentially mixtures, and therefore pass into one another insensi- bly. The wonder is, that rocks not only conform in some degree to a system, but that certain lithological types exhibit such an extraordinary persistence, being met with at the most remote quarters in typiwd development. "While the very nature of things thus excludes a rigid classification of rocks, observation clearly indicates the possibility of reducing them to a natural system.

rnfonnded Fears. Something is occa- sionally said about the expediency of avoid- ing heavy work in very warm weather. The "Lancet" evidently thinks there has been too much talk of the kind, and expresses views of its own on the matter. It says : " After it has been proved to demonstration that nothing whatever should be done, in schools, particularly, during hot weather, we shall be quite prepared to make common cause with the school-children in the en- deavor to demonstrate that it is undesirable to do anything in cold weather either. In short, let us give up eating, drinking, work- ing, playing, sleeping, and living, in the last

��issue, lest some harm should befall. It is rank nonsense to write and speak, as too many who ought to be better informed are writing and speaking just now, as though every act of existence were beset with peril. It would be better for all of us and the world at large if less ingenuity were spent on the invention of scares, and in the pitiful task of working on the fears of the public."

Caries of the Teeth. Caries of the teeth has been but little investigated scientifical- ly, according to Professor Busch, of Berlin, because in studying it the external hurtful processes have been alone considered, where- as the second important factor, the resist- ing power of the teeth, has been overlooked. It appears to be peculiar to man, having been observed in no animal ; but not to be characteristic of civilized man alone, for it has been observed in large collections of skulls, including those of prehistoric time. Some races are more disposed to it than others. Certain families are particularly predisposed to it. General habit of body has a pronounced influence upon its devel- opment, as well as certain peculiarities and crises of physical condition and disease. Disposition to caries shows itself even in the developing tooth in the composition of its enamel, which is undulating, whereas teeth with quite smooth enamel have much greater power of resistance. The enamel appears to be the only tissue in the body which is subject to no metabolism, and which remains quite unchanged. Every al- teration in it which is caused by external influences, and every defect of the enamel, remains during the whole of life, and can never be repaired. Dentine also shows dif- ferences in structure as regards its dispo- sition to caries. The dentine tubes cither run regularly closely side by side, when the teeth have greater power of resistance ; or they branch and surround cellular bodies, or even small air-vesicles, when the teeth fall an easy prey to caries. If dentine has been decalcified at any place by the action of acids, it undergoes putrefaction under the influence of bacteria which do not seem to belong to any particular species. Den- tine is sensitive, though nerve-filaments have not as yet been traced into it. Actual toothache does not occur in the course of

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��caries until it has reached the pulp. The inflammation of the pulp is particularly violent and painful, because the tissue is so richly provided with blood-vessels and nerve- filaments. As the products of inflamma- tion can not escape, they collect and work their way downward, where they produce the most painful inflammation of the roots and the periosteum. The chief object of the rational treatment of caries of the teeth consists in the removal of every particle of carious substance out of the diseased tooth and the protection of the sound dentine that has been exposed against external in- jurious influences by covering it with a fine substance which is not attacked by acids gutta-percha, cement, or gold. Although the dentine is not as unchangeable as en- amel, but manifests, by becoming firmer or softer, that it is not quite uninfluenced by tissue-changes, yet its caries is not an irrita- tive process that the dentine takes an active part in, but a passive process, and conse- quently the removal of all diseased portions and the protection of the non-carious part of the tooth suffices to stay the morbid pro cess completely.

Cooking by Steam. Professor Behrend, of Hohenheim, has described his experi- ments on the changes produced in the albu- minoid matter of various seeds and of pota- toes by steaming under high pressure. In a preliminary experiment, the author found that the albuminoids of lupine-seeds under- went considerable decomposition by heating with water under pressure, and that the de- composition was greater as the duration of the heating and the temperature increased. Ee, therefore, set to work to investigate whether the albumen was dissolved as well as decomposed, and, if so, what the quan- titative relations of these changes were in various seeds, and more especially in the raw starch material for the manufacture of alcohol. Yellow lupines, peas, Hungarian maize, dari (Sorghum tartaricum), and pota- toes in separate lots, nine months dug and just dug, were experimented upon. When the determinations were made, the contents of the flasks, especially when they were very starchy, became viscid and tenacious, like glue, at from 70 to 100 C, and at 130 C. they were almost clear, limpid

��liquids, with just a few flecks floating about, while, as the heating was continued, the masses became continually darker, the brownness being more or less intense, ac- cording as the substance was richer or poor- er in nitrogen. It is hence inferred that the brown coloration is the result of the decomposition of nitrogenous substances. In all cases an increase of the soluble nitro- gen was observed, especially with lupines and peas. The nitrogenous matter of maize seems less soluble, and not so easily at- tacked as that of lupines and peas. From the fact that the chief difference observed, after six hours of heating, was in the amounts of the albuminoid dissolved, it was inferred that the solution of albumi- noids precedes decomposition, and this was confirmed by subsequent experiment.

Geographical Conditions and Civiliza- tion. Mr. H. J. Mackinder shows, in a pa- per on " The Scope and Methods of Geogra- phy," how the distribution of men, their so- cial and political relations, and the elements of their civilization, are determined by fac- tors of physical geography and of geology back of it. " Each successive chapter post- ulates what has gone before. The sequence of argument is unbroken. From the posi- tion of the obstacles and the course of the winds may be deduced the distribution of rain. From the form and distribution of the wrinkle slopes and from the distribution of the rainfall follows the distribution of the drainage system. The distribution of soils is mainly dependent on the rock-struct- ure, and on a consideration of soil and cli- mate follows the division of the world into natural regions based on vegetation." Cer- tain conditions of climate and soil are needed for the aggregation of dense populations. A certain density of population seems ne- cessary to the development of civilization. Again, comparatively undisturbed strata usually underlie wide plains, and wide plains seem specially favorable to the development of homogeneous races, like the Russians and the Chinese. Yet, again, the distribution of animal, vegetable, and mineral products has done much to determine the local character- istics of civilization. An interesting chap- ter of geography deals with the reaction of man on nature. Man alters his environ-

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��ment, and the action of that environment on his posterity is changed in consequence. The relative importance of physical feat- ures varies from age to age according to the state of knowledge and of material civiliza- tion. The improvement of artificial light- ing has rendered possible the existence of a great community at St. Petersburg. The discovery of the Cape route to India and of the New World led to the fall of Venice. The invention of the steam-engine and the electric telegraph has rendered possible the great size of modern states. It must, however, be always borne in mind that the course of history at a given moment, wheth- er in politics, society, or any other sphere of human activity, is the product not only of environment but also of the momentum acquired, in the past ; and, for that reason, changes from what is established are not made so rapidly as they would otherwise be made.

Education and Work. Many persons believe that under the present systems of education, young people are acquiring a dis- taste for manual labor, and that there is, consequently, danger that the trade and ag- ricultural occupations will be deserted by all but the most inefficient classes of work- men. Much of the experience of English and American society is in favor of this view, and the tendencies in France appear to be in the same direction. As an offset to what may be said in favor of it, the Lon- don "Spectator" directs attention to the fact that no dislike of work, even of the roughest character, has appeared among two of the best -educated races. The Scotch, who have been taught for two hundred years, and are now far more thoroughly trained than English national school boys, show no disposition to avoid labor, but are remarka- ble for persistent and fairly contented in- dustry. The Prussian peasants, " who are as educated as the English will be twenty years hence, work exceedingly hard, and in the country, where their holdings arc their own, show none of the resentment at their fate which is manifested in the towns in the form of socialist aspirations. Gardeners, who all over Great Britain are the best in- structed of manual laborers, work, more es- pecially when working for themselves, with

��unusual diligence ; and it is matter of con- stant observation that a laborer who hap- pens by any accident to be a ' bit of a schol- ar,' can be depended upon when work press- es and every man is required. The people of Rome, who can read and write, are far more diligent than the Neapolitans, who can not ; and the best workmen in Italy are those who have passed through the army, and so obtained what is practically an edu- cation. There seems to be no a priori rea- son why it should be otherwise."

Anomalies in Hnman Teeth. Professor Busch has described before the Physiologi- cal Society of Berlin various anomalies in human teeth. Among them are anomalies in situation, as in case of the horizontal position of a wisdom-tooth, which, pressing against the third molar, produced inflam- mation in it ; the projection of teeth through the alveolar wall of the maxilla on the ante- rior or posterior side ; exchanges of situa- tion between certain teeth; and irregular- ities in the number of teeth. Among anom- alies in structure are enamel pearls, that is, drops of enamel adhering to the roots, and having no connection with the crown. Anomalies of size are rare ; enlargements affect the root more frequently than the crown. Anomalies of the root are some- times seen in curves, but more frequently as variations in the number of roots. Such anomalies are not frequent ; for, out of eleven thousand teeth examined, only about one hundred specimens had been found to present them. Swellings of the teeth are still more rare ; and no osseous coalescence of the teeth had ever been observed.

Intelligence of Fish. Mr. W. August Carter has been observing the habits and methods of fishes, and has thereby been led to assert that " the more we learn about them the more they shine out as an intelli- gent, crafty, and ingenious race " ; and he is convinced that some fish, at any rate, are capable of understanding and being un- derstood by one another. He has seen a shoal of carp approached while resting by an individual from another part of the pond ; when, on its arrival, the entire body of fish, following the lead of the solitary carp, migrated to the other side of the

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��pond whence the visitor came. He has observed fresh-water perch behaving in a similar manner. A further proof of the communicative capabilities of fish is afford- ed by the manner in which they oftentimes avoid the snares spread for them by men. They not only possess a keen sense of dan- ger, but must have the power of warning one another. Mr. Carter feels confident, from the result of his observations, that coarse fish are able to influence one anoth- er, and if this is the case with them, why not with others ? " It can not be credited," he says, "that Nature has denied to fish what she has freely bestowed upon all other animals, and therefore I think the further we go into the subject the more we shall realize that the gift of communication has been implanted in the nature of every creat- ure to a greater or less degree."

A Link between Invertebrates and Vcr- tcbrateSt Mr. W. Baldwin Spencer, of the University Museum, Oxford, in studying the anatomy and histology of the lizard-like reptile Hatteria punctata, found on the pi- neal body and under the parietal foramen, a rounded mass, provided with a well-marked nerve, which is evidently an eye. A de- pression of the skin of the head occurs im- mediately above the parietal foramen, but does not lead down to this structure, which is filled up with a plug of connective tissue that is specially dense around the capsule that envelops the eye. The capsule is also filled up behind with connective tissue, in which a blood-vessel, entering with the nerve, divides and ramifies. "It becomes extremely difficult," says the Rev. W. H. Dallinger, remarking on this discovery, " to conjecture what can be the use of so curi- ously placed, and at the same time so highly complex, an organ ; an eye so buried in its capsule and surrounding tissue, and so cov- ered with the skin of the head as to make it almost inconceivable that it can be af- fected by even the most intense light ; an eye placed, moreover, in a position that sug- gests no advantage to the present organ- ism." It is also placed in the head of ani- mals well endowed with the normal pair of vertebrate eyes ; and on examining it in different lizards it is found in different stages of uselessness, in some being quite

��isolated from the brain, and in others, as in this Hatteria, having a distinct nerve-con- nection with the hinder part of the pineal body. "The inference, therefore, appears inevitable that it is an atrophied organ ; an organ which the evolutional modifications of the original animal possessing this single eye have rendered in the course of ages de- void of function and needless ; but at the same time, and by this very means, it is in- dicative of the ancestry of the organism in which it lingers." Its structure is that of the invertebrate eye, being marked by the peculiar feature in which this eye is differ- ent from, or opposite in the arrangement of the parts to, that of the vertebrate eye. Its presence suggests an ancient connection be- tween the vertebrates and the tunicates, and their origin in one common stock ; and sup- plies a new and most direct evidence in favor of the doctrine of the evolution of animal life.

Specimens of Paleolithic Art. The riv- er Tardoire in La Charente, France, is fa- mous for the caves along its banks, out of which numerous evidences of occupation by prehistoric man have been collected from time to time. Among the objects which M. Eugene Paignon has recently found in one of the caves is a piece of reindeer-horn, perforated, of the form known as staff of command, which is covered with accurate and spirited engravings, and marked by work of such fineness that it can be seen best with a lens. On one of the faces of the staff is a representation of two seals, one of which is seen entire with its four limbs, the hinder limbs being faithfully rendered, and having five digits on each flap. The size of the tail is exaggerated. The body is covered with very evident hairs. The head is delicately executed, and the snout with its mustaches, the mouth, the eye, and the ear-orifice indicate genuine skill. The other seal is not entirely seen. It is larger and shows the marks of long hair on the neck. In front of the larger seal is a fish which may be a salmon or trout, for it is spotted like those fish, and its ventral fins are attached to the abdomen. Three plant-stems are seen near the fish. The opposite side of the horn is nearly cov- ered with two long and slender animals, one

�� � showing its head and the other one the end of its tail. They are probably intended to be seals. On the same side of the horn arc three figures of identical form, the meaning of which is not clear, and a figure that may be a hemipterous insect. 11. Gaudry has no doubt of the authenticity of this speci- men, for he is assured by M. Paignon, who is a lawyer and publicist of repute, and in- terested in prehistoric studies, that it was found in his presence by his own workmen while digging out the bone-earth from the bottom of the cave.

" Educating up." Dr. Andrew Wilson suggests that we might with advantage dis- miss some of the less useful topics from the curriculum of the common schools, and supplant them by other topics of vital inter- est to every class of the community. Boys and girls, for instance, are frequently kept working at modern languages, drawing, classics, and other branches, when the teach- ing of physiology, health, and domestic economy would be of infinitely greater ad- vantage to them in afterlife. Some people would think this to be educating down, but Dr. Wilson asks : " Is it certain that by limiting the ' extras ' or what are undoubt- edly often useless topics in education in so far as the social life of many of the pu- pils is concerned we should be educating down at all ? In all likelihood we should rather be practicing the reverse procedure. By imparting a knowledge of the laws of health and economy, we should be enabling the teacher to discharge his duties in a fuller and truer sense than before. . . . Individu- al culture of such subjects lies at the root of all national advance in health and pros- perity. As several writers have shown, the remedy for much of the misery and poverty now existent lies in the better use of the hours spent at school."

An Endnlatory Theory of Odors. M.

P. Leclerc has propounded a theory that odor is, like light and sound, a phenomenon of undulation. He cites in support of his view that many substances, like sulphur and copper, do not emit odors until they are rubbed, and it is more reasonable to suppose that the rubbings cause undula- tions than that under that condition the

��substances emit matter which can not be detected except as a smell. Again, arseni- ous acid when thrown upon a burning coal, gives out thick gray fumes and an odor of garlic. In the solid state it has no smell, and no more in the vaporous state if no chemical change takes place in volatilizing it. But, when it is thrown upon the hot coal, a reduction takes place to arsenic, that is volatilized and then reoxidized on com- ing in contact with the air, and we have a smell accompanying the chemical action the same as in many other cases we have light or heat in connection with it. M. Leclerc, continuing his experiments with a rather imperfect instrument, claims to have pro- duced interference of odors analogous with the interference phenomena of light.

Some British Weeds. British farms and gardens are troubled by about a hundred and thirty species of weeds, annuals and perennials, with about a dozen biennials. Among the most troublesome and mischiev- ous of them are the bind-weeds and the couch-grass, which will start to grow from so small a piece of root that it is almost impossible to get rid of them. The couch- grass is nearly in place in Italy, where the white, underground stems, which contain a considerable quantity of starch, are gath- ered and taken to market, to be sold as food for cattle and horses. A variety of this grass, called matt-grass, also finds a place in Holland, where it is put to use for binding together the sandy dunes and flat3 by the sea. Some weeds have a marvelous power of increase. The history of the ox- eye daisy in this country illustrates this property. Some seeds of the plant found their way in packages to the Island of Co- lonsay, in the west of Scotland; in the course of a few years the ox-eye had taken possession of the whole island. The com- mon yellow toad-flax was introduced as a garden-flower by a Mr. Ranstead, and i3 known as the Ranstead weed. Chickweed is said to have been introduced as a bird-seed. The Scotch thistle arrived in a bed-tick filled with its down. The down, having been replaced with feathers, was thrown away, and soon found a congenial home. Some American plants, particularly the wa- ter-weed (Anacharsis ahinasfrum), have naturalized themselves in Europe, and are becoming troublesome. All weeds are capable of being made useful as manure by plowing them in while they are green and before they have seeded.