Page:Popular Science Monthly Volume 1.djvu/647

From Wikisource
Jump to navigation Jump to search
This page has been validated.



pearance of the great glaciers, wide sheets of fresh water overspread some districts of the State. The forest-bed (consisting of roots, trunks, branches, and leaves of such trees as sycamore, beech, hickory, and red cedar) shows that by-and-by the fresh-water basins were in some places filled up, and the new soil covered with an abundant forest-growth. After this came a period of depression, when great deposits of gravel and sand gathered over the surface of the drowned land, and large bowlders and erratics were floated by ice from the north.

These and other matters of interest and importance will, no doubt, be fully treated of in the final report, which is to consist of four volumes, the first two being devoted to the geology and paleontology of the State, the third to its economic geology, and the fourth to its agriculture, botany, and zoology. A large collection of fossils has been made, many species being new to science. It is to be hoped that the good people of Ohio will not grudge the money that will be required for the adequate representation and description of these remains, but that, when published, the final report will be found in every way as complete as those admirable works which have been issued by other States of the Union. Prof. Newberry seems to have little doubt that it will be so, for he thinks that the value and significance of fossils are coming to be generally appreciated. "There are, however," he says, "yet some intelligent men, even editors and members of Legislatures, who cherish the notion that there is nothing which has any value in this world but that thing which has 1 dollar in it, and that so plainly visible as to be seen by them. Such men, to quote the language of one of them, 'don't care a row of pins for your clams and salamanders, but want something practical.'" This "practical" man must surely have been related to that colonial official who is said to have objected strongly to the expense of "engraved portraits of extinct bugs and beetles," as he irreverently styled certain Silurian fossils. But the day of such wiseacres has gone past, and it may be confidently expected that Dr. Newberry and his colleagues will have no difficulty in getting the necessary funds voted for the completion of their important survey.—Nature.


Experiments on the Solar Spectrum.—Some experiments recently published by Dr. John W. Draper, of the New York University, on the heat of different portions of the solar spectrum, will change, in several important particulars, the views hitherto held on that subject.

Until now, it has been supposed that the heat of the spectrum is greatest below the red region, and that it gradually declines as the thermometer passes through the orange, yellow, green, blue, indigo, and violet, successively.

Dr. Draper shows that, while this is true as a matter of observation, the general conclusion drawn from it is altogether incorrect. In the prismatic spectrum the red and less refrangible colors are compressed together, the violet and more refrangible are expanded. This distortion is necessarily due to the action of the prism itself. But, in the diffractive spectrum, formed by lines drawn with the point of a diamond on glass, the arrangement of the colors is altogether different; they are placed according to their wave-lengths.

Dr. Draper proves that, for the correct solution of this problem of the distribution of heat, the visible spectrum alone should be employed, the ultra-red and ultra-violet invisible rays being removed. He next finds the centre of the visible spectrum, proving that it is a little beyond the sodium-line D. He then, by the aid of a silver mirror, collects all the less refrangible rays up to this centre into one focus, and all the more refrangible rays from this centre into another focus, and measures the heat of each. On the received view, the former of these foci should contain nearly all the heat, the latter little or none. In several hundred experiments in which exact measures have been made, it turns out that the heat is the same in both.

From this, some very remarkable results follow. Among them we may mention, that all the rays of the spectrum, irrespective of their color or wave-length, have equal heating-power; and that, in fact, the heat manifested in any part of the spectrum is due to the stoppage of the motion of the