Kitabı oku: «Appletons' Popular Science Monthly, April 1899», sayfa 14

Fragments of Science

The Nernst Electric Lamp.– Prof. Walter Nernst, of the University of Göttingen, has recently devised an electric lamp which promises to be an important addition to our present methods of lighting. The part of the lamp which emits the light consists of a small rod of highly refractory material, said to be chiefly thoria, which is supported between two platinum electrodes. The rod is practically a nonconductor when cold, but by heating it (in the smaller sizes a match is sufficient) its conductivity is so raised that a current will pass through it; after the current is once started the heat produced by the resistance of the rod is sufficient to keep up its conductivity, and the latter is raised to a state of intense incandescence, and gives out a brilliant white light. As the preliminary heating by means of a match or other flame would in some cases be an inconvenience, Professor Nernst has devised a lamp which, by means of a platinum resistance attachment, can be started by simply turning a switch. The life of the rods is about five hundred hours. The lamps are said to work equally well with either alternating or direct currents, and there is no vacuum necessary. If this lamp proves a success as a commercial apparatus, it will be but another example of how slight a matter may make all the difference between success and failure. There have been numerous experimenters trying for the last ten years, and in fact ever since the appearance of the arc lamp, to utilize in an electric lamp the great light-giving power of the refractory earths in a state of incandescence; but, owing to their high resistance at ordinary temperatures, no results were obtained until Professor Nernst thought of heating his thoria rod, and this simple procedure seems to have solved the whole difficulty. It is claimed that the Nernst lamp is a much more economical transformer of electricity into light than the present incandescent electric lamps. An apparatus called a kaolin candle, which has been suggested as an anticipation of Professor Nernst's lamp, was constructed by Paul Jablochkoff in 1877 or 1878. It consisted of a strip of kaolin, along which ran a "match" of some conducting material. The current was passed through this "match" until the kaolin strip became heated sufficiently to become a conductor itself. The lamp did not, however, prove a commercial success.

Laws of Climatic Evolution.– The problem of the laws of climatic evolution was characterized by Dr. Marsden Manson, in a paper read at the British Association, as one of the grandest and most far-reaching problems in geological physics, since it embraces principles and laws applicable to other planets than ours. After presenting a formulation of those laws, the author pointed out that in consequence of their working, a hot spheroid rotating in space and revolving about a central sun, and holding fluids of similar properties to water and air within the sphere of its control, must pass through a series of uniform climates at sea level, gradually decreasing in temperature and terminating in an ice age, and that this age must be succeeded by a series of zonal climates gradually increasing in temperature and extent. The conclusions thus reached were that in the case of the earth zonal distribution of climates was inaugurated at the culmination of the ice age, and is gradually increasing in temperature and extent by the trapping of the solar energy in the lower atmosphere, and that the rise has a moderate limit; that the ice age was unique and due to the physical properties of water and air, and to the difference in specific heat of land and water; and that prior to the ice age local formation of glaciers could occur at any latitude and period. Dr. Manson then observed that Jupiter was apparently in a condition through which the earth has already passed, and Mars was in one toward which the climatic evolution of the earth was tending.

Poisonous Plants.– Statistics in regard to poisonous plants are lacking on account of a general ignorance of the subject, and it is therefore impossible to form even an approximate estimate of the damage done by them. Besides the criminal uses that may be made of them, there are some other problems connected with them that are of general public interest. The common law of England holds those who possess and cultivate such plants responsible for damages accruing from them; and a New York court has awarded damages in a case of injury from poison ivy growing in a cemetery. In order to obtain information on the subject, the botanical division of the Department of Agriculture arranged to receive notices through the clipping bureaus of the cases of poisoning recorded in the newspapers. Thus through the persons named in the articles or through the local postmaster it was put in correspondence with the physician in the case, who furnished the authentic facts. A large number of correct and valuable data were thus secured. It is proved by these facts that all poisonous plants are not equally injurious to all persons nor to all forms of life. Thus poison ivy has no apparent external effect upon animals, and a few of them eat its leaves with impunity; and it acts upon the skin of the majority of persons with varying intensity – on some hardly at all, while others are extremely sensitive to it. A similar variability is found in the effects of poisonous plants taken internally. In some cases often regarded as of that kind, death is attributable not to any poison which the plant contains, but to immoderate or incautious eating, or to mechanical injury such as is produced in horses by the hairs of crimson clover, or to the effect of parasitic growths, such as ergot on rye. Excluding all which operate in these ways, there are, however, a large number of really poisonous plants, the properties of which are comparatively unknown. It is concerning these that information has been sought by the botanical division. Its report contains descriptions of about forty plants, with figures, belonging to seventeen families.

The United States Biological Survey.– The Biological Survey of the United States Department of Agriculture aims to define and map the agricultural belts of the country in order to ascertain what products of the soil can and what can not be grown successfully in each, to guide the farmer in the intelligent introduction of foreign crops, and to point out his friends and his enemies among the native birds and animals. For information on these subjects so important to him the farmer has had to rely on his own experiments or those of his neighbors, often carried on at enormous cost to persons little able to bear it. The Survey and its predecessor, the division of ornithology and mammology, have had small parties in the field traversing the public domain for the purpose of studying the geographic distribution of our native land animals and plants and mapping the boundaries of the areas they inhabit. It was early learned that North America is divisible into seven transcontinental belts or life zones and a much larger number of minor areas or faunas, each characterized by particular associations of animals and plants. The inference was natural and has been verified that these same zones and areas, up to the northern limit of profitable agriculture, are adapted to the needs of particular kinds or varieties of cultivated crops. The Survey is engaged in tracing as precisely as possible the actual boundaries of these belts and areas, and in finding out and designating the varieties of crops best adapted to each. In this undertaking it aims to point out such exotic products as, from their importance in other lands, are likely to prove of value if introduced on fit soils and under proper climatic conditions. The importance of this work will be realized when it is recollected that all the climatic life zones of the world, except the hottest tropical, are represented in our country. The colored maps prepared by the Survey furnish the best guide the farmer can have for judging what crops will be best adapted for his particular region; and in connection with the work of the entomologist, show the belts along which noxious insects are likely to spread. The report of the Survey, prepared under the direction of its chief, C. Hart Merriam, though full of valuable information not before presented consecutively, is preliminary and only touches the edge of a subject which is susceptible of copious elaboration, and is destined to be worked up with immense profit.

A Neolithic Lake Dwelling.– A crannog, or lake dwelling, discovered in the summer of 1898 on the banks of the Clyde, has received much attention from English archæologists because of its unique situation on a tidal stream, and of its being apparently neolithic or far more ancient than any other crannog yet examined, in all others the relics being of the bronze age. Careful excavations have been made in it and are still in progress, and the refuse mound of the former settlement has been sifted, with results that have made it plain that there were design and execution in the building, and that it was occupied and inhabited for a long period. Positive evidence of fire is afforded in the shape of numerous firestones and calcined embers, and indications of the condition of life at the period are given by the implements, ornaments, and tools recovered. The crannog is about sixteen hundred yards east of the Castle Rock of Dumbarton, and about fifty yards from the river at low tide, but is submerged when the tide is in to a depth of from three to twelve feet, and is one hundred and eighty-four feet in circuit. The piles in the outer circle are of oak, which below the mud surface is still quite fresh. The transverse beams and pavement inside are of wood of the consistence of cheese – willow, alder, and oak – while the smaller branches are of fir, birch, and hazel, with bracken, moss, and chips. The stones in the outer circle and along the causeway leading to the dwelling place seem to have been set in a methodical order, most of the bowlders being about a lift for a man. The refuse mound extends for about twelve feet outside for the greater part of the circuit, and here most of the bone and flint implements have been discovered. The largest article found in the site was a very fine canoe, thirty-seven feet long and forty inches beam, dug out of a single oak tree, which lay in what has proved to have been a dock. A curious ladder was also found here, the rungs of which were cut out of the solid wood, and which has somewhat the general appearance of a post of a post-and-rail fence. The exploration of the site is much interfered with by the rising of the tide, which covers the crannog for a considerable time every day. All the relics found – consisting chiefly of objects of bone, staghorn, jet, chert, and cannel coal, with some querns, the canoe, ladder, etc. – have been placed in the museum at Glasgow.

Portland Cement.– The following facts are taken from an address delivered before the Franklin Institute by Mr. Robert W. Lesley: "It was not until the end of the last century that the true principles of hydraulic cement were discovered by Smeaton, who, in the construction of the Eddystone Lighthouse, made a number of experiments with the English limestones, and laid down, as a result, the principle that a limestone yielding from fifteen to twenty-five per cent of residue when dissolved in hydrochloric acid will set under water. These limestones he denominated hydraulic limestones, and from the principle so laid down by him come the two great definitions of what we now know as cement, namely, the natural and artificial cements of commerce. The natural variety, such as the Rosendale, Lehigh, and Cumberland cements, was first made by Joseph Parker in 1796, who discovered what he called 'Roman cement,' based upon the calcination at low temperatures of the nodules found in the septaria geological formation in England. This was practically the first cement of commerce, and gave excellent results. Joseph Aspdin, a bricklayer or plasterer, took out a patent in England in 1824 on a high-grade artificial cement, and, at great personal deprivation, succeeded in manufacturing it on a commercial scale by combining English chalks with clay from the river beds, drying the mixed paste, and after calcining at high heat the material thus produced, grinding it to powder. This cement, which was the first Portland cement in the market, obtained its name from its resemblance when it became stone to the celebrated Portland stone, one of the leading building materials in England. The rocks used in the manufacture of Portland cement are very similar to those from which natural cement is made. The various layers in the natural rock may vary in size or stratification, so that the lime, alumina, and silica may not be in position to combine under heat, or there may be too much of one ingredient, or not enough of the others in close proximity to each other. In making Portland cement, these rocks, properly proportioned, are accordingly ground to an impalpable powder, the natural rock being broken down and the laminæ distributed in many small grains. This powder is then mixed with water, and is made into a new stone in the shape of the brick, or block, in which all the small grains formerly composing the laminæ of the original rock are distributed and brought into a close mechanical juxtaposition to each other. The new rock thus made is put into kilns with layers of coke, and is then calcined at temperatures from 1,600° to 1,800°. The clinker, as it comes from the kiln, is then crushed and ground to an impalpable powder, which is the Portland cement of commerce. Portland cement may be made from other materials, such as chalk and clay, limestone and clay, cement rock and limestone, and marls and clays. In every case the principle is the same, the breaking down and the redistributing of the materials so that the fine particles may be in close mechanical union when subjected to the heat of the kiln."

The French Nontoxic Matches.– It is believed, by Frenchmen at least, that the problem long sought, of finding a composition for a match head in which all the advantages of white phosphorus shall be preserved while its deleterious qualities are eliminated or greatly reduced, has been solved in the new matches which the French Government has placed upon the market. These matches are marked S. C., by the initials of the inventors, MM. Sévène and Cahen, are made in the factories at Trélazé, Begles, and Samtines, and have been well received by the public. In preparing the composition, the chlorate of potash of the old flashing and safety matches has been retained, and the sesquisulphide of phosphorus is used instead of the white or red phosphorus of the old matches. The latter substance, besides the indispensable qualities of fixity and resistance to atmospheric influences, has the two important properties of inflaming at 95 °C., much nearer the igniting point of white phosphorus (60 °C.) than of red (260 °C.), and being therefore easier to light; and of having a low latent or specific heat. With these properties embodied in the inflammable composition of the head, the new match is expected to be comparatively free from accidental explosions during manufacture and export, to take fire by friction, and to burn steadily and regularly. The expectation has so far been fulfilled. The phosphorus compound has a special odor, in which the sulphur characteristic predominates, but, not boiling under 380 °C., does not become offensive in the shops; and the match heads made with it do not emit the phosphorescence which is often exhibited by matches made with white phosphorus. It is only feebly toxic by direct absorption, experiments on guinea pigs indicating that it is only about one tenth as much so as white phosphorus.

Trees as Land Formers.– John Gifford, in a paper presented to the Franklin Institute on Forestry in Relation to Physical Geography and Engineering, mentions as illustrating the way forests counteract certain destructive forces, the mangrove tree as "the great land former which, supplementing the work of the coral polyp, has added to the warm seashore regions of the globe immense areas of land." The trees grow in salt water several feet deep, where their labyrinth of roots and branches collect and hold sediment and flotage. Thus the shore line advances. The seeds, germinating on the plant, the plantlets fall into the water, float away till their roots touch the bottom, and there form the nucleus of new islands and life. The forest constantly improves the soil, provided the latter is not removed or allowed to burn. The roots of trees penetrate to its deeper layers and absorb great quantities of mineral matters, a large percentage of which goes to the leaves, and is ultimately deposited on the surface. "The surface soil is both enriched by these mineral substances and protected by a mulch of humus in varying stages of decomposition. As the lower layers rot, new layers of leaves and twigs are being constantly deposited, so that the forest soil, in the course of time, fairly reeks with nourishing plant food, which seeps out more or less to enrich neighboring soils." The forest is also a soil former. "Even the most tender rootlet, because of its acidity, is able to dissolve its way through certain kinds of rock. This, together with the acids formed in the decomposition of humus, is a potent and speedy agent in the production of soil. The roots of many species of trees have no difficulty whatever in penetrating limestone and in disintegrating rocks of the granitic series. As the rock crumbles, solid inorganic materials are released, which enrich neighboring soils, especially those of the valleys in regions where the forest is relegated to the mountain sides and top, as should be the case in all mountainous regions. In view of the destruction caused by mankind, it is a consoling fact that Nature, although slowly, is gradually improving her waste lands. If not interrupted, the barest rock and the fallowest field, under conditions which may be called unfavorable, will become, in course of time, forest-clad and fertile. The most important function of the forest in relation to the soil, however, is in holding it in place and protecting it from the erosive action of wind and rain."

The Atlantic Slope.– The Atlantic slope of the United States is described in the New Jersey State Geological Survey's report on the Physical Geography of the State as "a fairly distinct geographical province. Its eastern boundary is the sea; its western boundary on the north is the divide between the drainage flowing southeast to the sea and that flowing northeast to the St. Lawrence. Farther south its western limit is the divide between the streams flowing east to the Atlantic and those flowing west to the Ohio and Mississippi Rivers." The line between it and the geographical province next west follows the watershed of the Appalachian system of mountains. It is divided, according to elevations, into several subprovinces, all of which elongate in a direction roughly parallel to the shore. Next to the coast there is usually a belt of lowland, few or many miles wide, called the Coastal Plain. Inland from the Coastal Plain is an intermediate height, between the Coastal Plain to the east and the mountains to the west, known in the South as the Piedmont Plateau. The mountainous part of the slope constitutes the third province, known as the Appalachian Zone. The Atlantic slope may be divided into two sections – a northern and a southern – in which the Coastal Plain is narrow and wide respectively. These two sections meet in New Jersey, where the division runs from the Raritan River, just below New Brunswick, to Trenton. South of this line the Coastal Plain expands, and all considerable elevations recede correspondingly from the shore. These three subprovinces are especially well shown in the southern section of the Atlantic slope. They are less well developed in the northern section, and even where the topography is comparable the underlying rock structure is different. In New Jersey a fourth belt, the Triassic formation, is interposed between the Coastal Plain and the Highlands corresponding to the Piedmont Plateau. North of New Jersey the Coastal Plain has little development, though Long Island and some small areas farther east and northeast are to be looked upon as parts of it.

American Fresh-water Pearls.– The facts cited by Mr. George F. Kunz in his paper, published in the Report of the United States Fish Commission, on the Fresh-water Pearls and Pearl Fisheries of the United States, give considerable importance to this feature of our natural history. The mound explorations attest that fresh-water pearls were gathered and used by the prehistoric peoples of the country "to an extent that is astonishing. On the hearths of some of these mounds in Ohio the pearls have been found, not by hundreds, but by thousands and even by bushels – now, of course, damaged and half decomposed by centuries of burial and by the heat of superficial fires." The narratives of the early Spanish explorers make several mentions of pearls in the possession of the Indians. For a considerable period after the first explorations, however, American pearls attracted but little attention, and "for some two centuries the Unios [or 'fresh-water mussels'] lived and multiplied in the rivers and streams, unmolested by either the native tribes that had used them for food, or by the pioneers of the new race that had not yet learned of their hidden treasures." Within recent years the gathering of Unio pearls has attained such importance as to start economical problems warranting and even demanding careful and detailed inquiry. The first really important discovery of Unio pearls was made near Paterson, N. J., in 1857, in the form of the "queen pearl" of fine luster, weighing ninety-three grains, which was sold to Eugénie, wife of Napoleon III, for twenty-five hundred dollars, and is now worth four times that amount. As a result the Unios at Notch Brook, where it was found, were gathered by the million and destroyed. Within a year fully fifteen thousand dollars' worth of pearls were sent to the New York market. Then the shipments gradually fell off. Some of the best American pearls that were next found were at Waynesville, Ohio, where Mr. Israel H. Harris formed an exceedingly fine collection. It contained more than two thousand specimens, weighing more than as many grains. Among them were one button-shaped on the back and weighing thirty-eight grains, several almost transparent pink ones, and one showing where the pearl had grown almost entirely through the Unio. In 1889 a number of magnificently colored pearls were found at different places in the creeks and rivers of Wisconsin, of which more than ten thousand dollars' worth were sent to New York within three months. These discoveries led to immense activity in pearl hunting through all the streams of the region, and in three or four seasons the shells were nearly exhausted. The pearl fisheries of this State have produced at least two hundred and fifty thousand dollars' worth of pearls since 1889. Another outbreak of the "pearl mania" occurred in Arkansas in 1897, and extended into the Indian Territory, Missouri, Georgia, and other States.

Distribution of Cereals in the United States.– To inquiries made preparatory to drawing up a report on the Distribution of Cereals in North America (Department of Agriculture, Biological Survey), Mr. C. S. Plumb received one thousand and thirty-three answers, eight hundred and ninety-seven of which came from the United States and the rest from the Canadian provinces. These reports showed that in many localities, particularly in the East and South, but little attention is paid to keeping varieties pure, and many farmers use mixed, unknown, or local varieties of ordinary merit for seed. In New England but little grain is grown from sowing, owing to the cheapness of Western grain, and wheat is rarely reported. Oats are now mostly sown from Western seed, and the resulting crop is mown for hay, while most of the corn is cut for green fodder or silage. On certain fine lowlands – as, for example, in the Connecticut Valley – oats, and more especially corn, are often grown for grain. While reports on most of the cereals were rendered from the lower austral zone, or the region south of the Appalachians and the old Missouri Compromise line, this region, except where it merges with the upper austral or the one north of it, is apparently outside the area of profitable cultivation of wheat and oats. In Louisiana and most of the other parts of the lower austral, except in northern Texas and Oklahoma, wheat is almost an unknown crop. The warm, moist climatic conditions here favor the development of fungous diseases to such a degree that the plants are usually ruined or greatly injured at an early stage of growth. In Florida, as a rule, cereals are rarely cultivated except on the uplands at the northern end of the State. In a general way, corn and wheat are most successfully grown in the upper austral zone, or central States, while oats are best and most productive in the transition zone (or northern and Lake States and the Dakotas), or along the border of the upper austral and transition. The gradual acclimation of varieties of cereals, through years of selection and cultivation, has gone so far, however, that some varieties are now much better adapted to one zone than to another.

Spanish Silkworm Gut.– The business of manufacturing silkworm gut in Spain is a considerable industry. The method of preparation is thus described in the Journal of the Society of Arts: After the silkworm grub has eaten enough mulberry leaves, and before it begins to spin, which is during the months of May and June, it is thrown into vinegar for several hours. The insect is killed and the substance which the grub, if alive, would have spun into a cocoon is drawn out from the dead worm into a much thicker and shorter silken thread, in which operation considerable dexterity and experience are required. Two thick threads from each grub are placed for about four hours in clear cold water, after which they are put for ten or fifteen minutes in a solution of some caustic. This loosens a fine outer skin on the threads, which is removed by the hands, the workman holding the threads in his teeth. The silk is then hung up to dry in a shady place, the sun rendering it brittle. In some parts of the country these silk guts are bleached with sulphur vapor, which makes them beautifully glossy and snow-white, while those naturally dried have a yellowish tint. The quality of the gut is decided according to the healthy condition of the worm, round indicating a good quality and flat an inferior one.

The Nests of Burrowing Bees.– Prof. John B. Smith, having explained to his section of the American Association a method which has been successfully applied, of taking casts in plaster of Paris of the homes of burrowing insects, with their branchings, to the depth of six feet, described some of the results of its application. Bees, of the genus Calletes, dig vertically to the depth of eighteen inches or more, then burrow horizontally from two to five inches farther, and construct a thin, parchmentlike cell of saliva, in which the egg is deposited, with pollen and honey for the food of the larva. They then start a new horizontal burrow a little distance from the first, and perhaps a third, but no more. The vertical tubes are then filled up, so that when the bees come to life they must burrow from six to twenty-four inches before they can reach the surface. Another genus makes a twisted burrow; another makes a vertical burrow that may be six feet deep. About a foot below the surface it sends off a lateral branch, and in this it excavates a chamber from one to two and a half inches in diameter. Tubes are sent down from this chamber, as many perhaps as from six to twenty together, and these are lined with clay to make them water-tight. This bee, when it begins its burrow, makes an oblique gallery from four to six inches long before it starts in the vertical direction, and all the dirt is carried through this oblique gallery. Then the insect continues the tube vertically upward to just below the surface, and makes a small concealed opening to it here, taking care to pile no sand near it. This is the regular entrance to the burrow.

MINOR PARAGRAPHS

In a report of an inspection of three French match factories, published as a British Parliamentary paper, Dr. T. Oliver records as his impressions and deductions that while until recently the match makers suffered severely from phosphorus poisoning, there is now apparently a reduction in the severe forms of the illness; that this reduction is attributable to greater care in the selection of the work people, to raising the age of admission into the factory, to medical examination on entrance, subsequent close supervision, and repeated dental examination; to personal cleanliness on the part of the workers; to early suspension on the appearance of symptoms of ill health; and to improved methods of manufacture. The French Government is furthering by all possible means new methods of manufacture in the hope of finding a safer one; and a match free from white phosphorus and still capable of striking anywhere is already manufactured.

A mechanical and engineering section is to be organized in the Franklin Institute, Philadelphia, to be devoted to the consideration of subjects bearing upon the mechanic arts and the engineering problems connected therewith. The growth of the various departments of this institution – which has been fitly termed a "democratic learned society," from the close affiliation in it of the men of the professions and the men of the workshops – by natural accretion, and the steadily growing demands for the extension of its educational work during the past decade, have increased the costs for maintenance and administration and have been the cause of a deficit in nearly every year. A movement is now on foot, approved by the board of managers, and directed by a special committee, to secure for it an endowment, toward which a number of subscriptions ranging from two hundred and fifty to twenty-five hundred dollars have already been received.