Popular Science Monthly/Volume 4/February 1874/Miscellany
New Material for Dental Plates.—Among the novelties exhibited at the American Institute Fair is a new base for artificial teeth, the invention of a New York dentist. It consists mainly of fish-scales, which, dissolved and combined with certain fibrous and adhesive substances, form a compound that is said to be well adapted for use as dental plates. Greater strength, durability, and lightness, and freedom from all taste, are the advantages claimed for it over the materials in common use. It is capable of receiving a fine polish, and may also be readily colored to any desired tint, qualities which adapt it to a great variety of purposes outside of dentistry. It is also said to be an excellent material for waterproofing cloth.
Meteorological.—In his report for 1872, Mr. Daniel Draper, Director of the Meteorological Observatory in Central Park, considers the following points:
1. "Has the summer temperature of the Atlantic States undergone any modifications?
2. "What is the direction in which atmospheric fluctuations cross the United States?
3. "Is it possible to trace the passage of American storms across the Atlantic, and predict the time of their arrival on the European coast?"
By carefully-arranged tables, he shows that no change has taken place in summer temperature, and concludes that "the mean heat of summer and the mean cold of winter are the same now as they were more than a century ago."
These conclusions are from observations made in Boston, New Haven, New York, Philadelphia, and Charleston. It may be added that, in his former reports, it was shown that over the same areas the annual rainfall has neither increased nor diminished.
The movement of atmospheric fluctuations is illustrated by diagrams founded on observations at the Observatory, and the daily maps published at Washington. It appears that these movements are not all cyclonic—many are like waves of the ocean, long and straight, and have a forward motion. This motion over the United States is eastward. The velocity of this motion has been determined in a great number of instances for the years 1869, 1870, 1871, and 1872. During the last year the highest forward velocity was 569 miles in twenty-four hours; the lowest velocity, 82 miles in twenty-four hours. The highest velocity recorded was about 29 miles an hour, or 690 miles in twenty-four hours; this occurred on the 28th of March, 1870. The time required to cross the Atlantic varied from ten to twenty days. It sometimes happens that storms which leave our coast three and four days apart arrive on the coast of Europe together, and, in such cases, the storm is usually severe. The observations made show that, out of eighty-six storms expected to cross the Atlantic, only three seem to have failed. Moreover, it is shown that the direction of the movement is maintained, so that it may be known several days in advance what part of the coast of Europe will be covered by the advancing storm.
The great practical value of these observations and reports will be at once recognized, and the conclusions they suggest and confirm are among the most interesting of the results of modern scientific research.
Sewage Fertilization.—The following, from the report of the committee of the British Association on the "Purification and Utilization of Sewage," effectually disposes of some of the more important objections that have been urged against the use of sewage for fertilizing purposes:
"By properly-conducted sewage irrigation a solution is afforded to the question of sewage utilization. It has already been stated that a precipitation process, or some clarifying process, may be found useful: in all instances it is essential that the land should be well underdrained, and that the sewage should all pass through the soil, and not merely over it; otherwise, as has been shown, it will only occasionally be satisfactorily purified. The catch-water, or, as the committee has termed it, the "supersaturation" principle, is not defensible either on agricultural, chemical, or sanitary principles. An irrigation farm should therefore carry out intermittent downward filtration on a large scale, so that the sewage may be always thoroughly purified, while at the same time the maximum of utilization is obtained.
"It is certain that all kinds of crops may be grown with sewage, so that the farmer can grow such as he can best sell. Nevertheless, the staple crops must be cattle-food, with occasional crops of corn; and it is also certain, from the analysis of the soil, that it has become very much richer, and that the manurial constituents of the sewage accumulate in it. Cattle should be fed on the farm, which leads to a vast increase in the production of meat and milk, the great desiderata of the population producing the sewage. Thus the system of farming must be specialized and capital concentrated, the absence of which conditions has proved a great barrier to the satisfactory practical solution of the sewage question.
"The committee has not been able to trace any ill effects to the health of the persons living around sewage farms, even when badly conducted; nor is there any proof whatever that vegetables grown thereon are in any way inferior to those grown with other manure. On the contrary, there is plenty of evidence that such vegetables are perfectly suited for the food of man and beast, and that the milk given by cows fed on sewaged grass is perfectly wholesome; thus Mr. Dyke, Medical Officer of Health of Merthyr Tydfil, states that, since the abundant supply of milk from the cows fed on irrigated grass, the children's mortality has decreased from 48, 50, and 52 per cent, of the total deaths, to only 39 per cent., and that so far from diarrhoea having been made more prevalent by the use of sewaged cabbages, 'last year the Registrar-General called attention to the fact that diarrhœa was less prevalent in Merthyr than in any place in England and Wales;' and he expressed his belief in 'the perfect salubrity of the vegetable food so grown.'
"With regard to the assumption which has been made that entozoic diseases would be propagated by irrigation, all the evidence that the country has been able to collect, and more especially the positive facts obtained by experiments, are against such an idea; and the committee is of opinion that such disease will certainly not be more readily propagated by sewage irrigation than by the use of human refuse as manure in any other way, and probably less if the precaution be taken of not allowing the animals to graze, but always having the grass cut and carried to them."
Length of Thread of the Silk-worm.—Prof. Riley, of St. Louis, informs us that the calculation, on page 663 of the last volume, as to length of thread and weight of cocoon spun by the mulberry silk-worm, is altogether exaggerated. Instead of the thread being 11 miles in length, it averages not much more than half a mile, and seldom exceeds 1,000 yards; while a single mile, instead of 28 miles of it, would weigh about 151⁄2 grains.
The Constitution of Carboniferous Strata.—At a general meeting of the British Association, Prof. W. C. Williamson delivered an interesting discourse on "Coal and Coal Plants." The speaker said that most men are now agreed as to the vegetable origin of coal, and the drift theory of its accumulation. It was once a vegetable soil, which accumulated under the shade of primeval forests, growing on areas of depression. In time the land sank beneath the sea, and the vegetable elements were buried under layers of sand and mud, accumulations of which again restored the area to the sea-level, when spores of plants once more germinated in a blue mud, and the succession of phenomena which had previously occurred was again renewed. The frequent repetition of these changes, finally, resulted in the accumulation of the thousands of feet composing the vertical series of rocks which are termed the carboniferous strata. Attention had been called by Prof. Huxley to some minute coin-like bodies which are very abundant in some coals, and which had been previously noticed by Witham, Dawson, and others. The larger of these bodies Huxley regarded as spore-cases, and the smaller as spores, while he considered that their disintegration had led in most cases to the formation of the bulk of what we call coal.
Prof. Williamson showed in detail that these were not spore-cases, but two kinds of spores—microspores and macrospores—such as severally occur in the upper and lower portions of the fruits of many living club-mosses. Their sizes and structure demonstrate the truth of this conclusion, which is further sustained by the fact that spore-cases are not deciduous, but spores are; and these objects, having fallen in such vast myriads from gigantic club-mosses, can only have been deciduous organs. The lecturer then gave reasons for concluding that these spores had played a much more limited part in the origin of coal than Huxley had assigned to them. According to Huxley, coal is composed of mineral charcoal and coal proper—the latter term being equivalent to spores altered or unaltered. Prof. Williamson, on the other hand, recognized three such elements: mineral charcoal, that is, fragments of fossil wood retaining its structure; coal proper, that is, mineral charcoal disorganized; and spores in various states.
We now distinguish in coal three groups of fossil plants: 1. Those of which we have the form but not the organization: 2. Those of which we have both form and organization; 3. Those of which we know the structure, but are ignorant of the outward form. What has yet to be done is the correlation of the first and last of these three groups. Brogniart long ago showed that most of the coal-plants were cryptogamic—chiefly calamites (allied to living horse-tails); lepidodendra (represented by the club-mosses); ferns, and plants supposed to represent pines and firs of the group known as gymnospermous exogens.
Leached Ashes as a Fertilizer.—In a report to the Connecticut State Board of Agriculture, Prof. S. W. Johnson gives the results of some analyses made by himself of specimens of leached ashes used for fertilizing purposes. By these analyses leached ashes are found to contain: less than one per cent, of potash; a large proportion of water (not less than 35 per cent.); considerable sand or soil, and unburned coal, amounting to from 6 to 15 per cent., when not intentionally or largely adulterated; about 45 per cent, carbonate of lime, which is the chief fertilizing element in leached ashes; a little more than 1 per cent, of phosphoric acid, and 3 to 4 per cent, of magnesia. They contain no nitrates, but the carbonate of lime in them favors the development of nitrates when they are incorporated with the soil, especially in conjunction with animal manures.
Prof. Johnson states that the price of this material is 35 cents per 100 lbs., or $7.00 per ton. Its fertilizing value lies exclusively in the 20 or 30 lbs. of lime, 31⁄2 of magnesia, 11⁄2 of phosphoric acid, and 1 or 2 lbs. of potash in each 100 lbs. But these materials may be procured in other forms, as follows: 35 lbs. of fresh-burned oyster-shell, or stone-lime, will furnish the lime; 15 lbs. of any good superphosphate will supply the phosphoric acid; the magnesia and potash together may be obtained in 40 lbs. of German potash salts, and there will then be 4 or 5 lbs. of potash and 6 lbs. of sulphuric acid extra.
If the lime be slaked with water in which the superphosphate and potash salts have been soaked and partially dissolved, the resulting mass will contain not only all the fertilizing elements of 100 lbs. of leached ashes and more, but these elements will be in such a state of fine division as to render the mixture in all respects equal to the ashes themselves.
From these data any one can readily calculate the cost in his own locality of a substitute for leached ashes. "It must not be forgotten," adds Prof. Johnson, "that a mixture made of fresh-burned lime should be allowed to become mild by exposure to the air, or its peculiar effects on the soil should be anticipated and provided for."
Age of Metamorphic Rocks.—"The Metamorphism of Rocks" is the title of a paper read at the Association meeting, by Prof. T. Sterry Hunt. The author briefly noticed the changes produced in rocks by the action of water, air, and various gases. While some geologists had supposed that many of these, such as gneiss, greenstone, serpentine, talcose, and chloritic rocks, were igneous products, more or less modified by subsequent chemical action, others maintained that they were the result of aqueous sedimentation, and subsequently crystallized. This was the teaching of Hutton; and when early in the present century the crystalline rocks of the Alps were shown to rest on uncrystalline fossiliferous strata, it was suggested that the overlying crystalline strata were newer rocks which had undergone a metamorphism, to which those just beneath had not been subjected. This view spread until the great crystalline centre of the Alps was considered to be in part of secondary and even of tertiary age.
The author detailed the course of study by which he was led to question this view, and showed that there is no evidence in the Alps to support it; that Sedgwick and Nicoll had discredited the palæozoic age of the crystalline schists regarded by Murchison as Cambrian and Silurian; and, finally, gave the observations by which he had satisfied himself that the crystalline rocks of the Green and White Mountains, and their representatives in Quebec, New Brunswick, and on the Blue Ridge, were more ancient than the oldest Cambrian or primordial fossiliferous strata.
Tests for Glycerine.—The so-called pure glycerine of commerce, according to the Journal of Applied Chemistry, is often contaminated with metallic chlorides. Traces of ammonia are also sometimes present; and it not unfrequently contains oxalic acid or soda. The first-named impurity may be detected by diluting the glycerine with twice its volume of water and adding nitrate of silver. If the glycerine only becomes opalescent, the quantity of chlorides is not great enough to be injurious, but, if a flaky precipitate is produced, it indicates that the glycerine is unfit for medicinal use. To detect ammonia, mix the glycerine with its own volume of caustic potash, and bring a glass rod previously dipped in dilute muriatic acid over the mixture. If ammonia is present in injurious quantity, whitish vapors of chloride of ammonium will be formed. Oxalic acid may be detected, by adding lime-water, acetate of lime, or a mixture of chloride of calcium and acetate of soda. If the glycerine becomes turbid within five minutes after the reagent is added, it should be rejected. Traces of soda can only be revealed by evaporating the glycerine to dryness, and testing the residue.
American Origin of the Garden Raspberry.—Although the garden raspberry (Rubus Idœus) was imported from Europe, yet Dr. Asa Gray has lately made known some facts that would seem to make it certain that this plant, which is not indigenous to Europe, is a native of Japan and North America. Wild specimens from British America and the Rocky Mountains, it seems, must be referred by the botanist to the cultivated species, Rubus Idœus. Prof. Areschoug, who has devoted special study to the Rubi of Europe, concludes that this species did not originally have its home in Europe, but that its origin is to be found in the east of Asia, namely, Japan and the adjacent countries, and perhaps in North America. He also thinks that "the Asiatic and North American floras have reciprocally mixed with each other by passing Behring Straits and the islands which in its neighborhood form a bridge between the two continents."
Rapidity of Vegetable Growth.—A writer in the Gardener's Chronicle gives some illustrations of the prodigious activity manifested in the growth of plants during a few weeks. The process of growth, being gradual and noiseless, and moreover of everyday occurrence, is generally disregarded. And yet, what a quantity of water must be absorbed and exhaled, how much air inhaled and exhaled, how much carbon fixed during the process! The writer gives some measurements of an ordinary plant, the Abies nordmanniana, a species of silver-fir, which will give a good idea of the rapidity of growth.
The shrub was only two feet six inches in height, and the number of young shoots of this year's growth on it 585. These shoots vary in length from half an inch to six inches, and their aggregate length is 1,171 inches, or nearly 98 feet. Dividing the aggregate of the shoots (1,171 inches) by their number (585), we find the mean length of the shoots to be about two inches. The average number of leaves on each inch of a number of shoots, taken at random, was 34, so that the total number of leaves on these 585 shoots may be set down at 39,814. Assuming each leaf to be only one inch in length—which is considerably under the mark, even when all the small, undeveloped leaves are taken into consideration—we should have for the leaves a length of about 3,501 feet, so that, in round numbers, we may say that, including the shoots and leaves, the growth in length alone of this very moderate-sized young tree, during this season, has amounted to the prodigious number of 3,600 feet; and, if the shoots and the leaves could all be placed end to end in a continuous line, they would extend considerably more than half a mile.
Action of the Sand-blast.—At a recent meeting of the British Microscopical Society, Mr. Wenham exhibited a piece of glass "ground" by the sand-blast process, which, under the microscope, presented a very different appearance from common ground glass. It is found that the glass or other material, worn away by the sand-blast, is not ground away at all, but broken up by a battering action, similar to that of leaden bullets against a block of granite. Hence it is that, although, by the usual grinding process, ordinary sea-sand can make no impression on corundum, a blast with a pressure of 300 pounds to the square inch will perforate it in a short time. Nay, even the diamond itself may thus be speedily worn away.
A polished glass surface, exposed for an instant to the sand-blast, shows an aggregation of points of impact, from which scales of fractured glass have broken away in an irregular radial direction. It appears as if a pellet of glass had been driven in by the collision of the sand, and the wedge-like action thus set up had driven away the surrounding glass. All these spots, or indentations, when tested by the polariscope, show a colored halo round each, proving that the glass surface is under strain and ready to yield to further fracture. The action, therefore, is not so much due to the hardness of the striking particles as to the force and velocity of impact. This is sufficiently great to destroy the cohesion of the material operated upon. The external layer is carried against the under stratum, and the material is crushed and disintegrated by a portion of its own body.