Page:Popular Science Monthly Volume 31.djvu/589

Rh were well shown. The investigation having been resumed in 1885, with a larger telescope, one hundred and seventeen stars within 1 degree of the pole, each of them no brighter than the fourteenth magnitude, left trails. The average deviation of the measures of the brightness of these stars on different photographs was less than a tenth of a magnitude, a greater accordance than is given by any other photographic method. A similar result was obtained from the Pleiades, of which group more than fifty stars left trails. Trails are now being photographed of all the stars north of -30° in all right ascensions, and the work has been completed for more than half of the sky. By photographing on the same plate polar stars near their upper and lower culminations, material has been accumulated for determining the atmospheric absorption on each night of observation. A study has been made of the application of photography to the transit-instrument. By placing a large prism in front of the object-glass, excellent stellar spectra have been obtained. An exposure of five minutes gives the spectra of all stars brighter than the sixth magnitude within a region 10° square. About half of the region north of -25° has been photographed in this way. With an exposure of an hour, the spectra of stars no brighter than the ninth magnitude are shown. Over a hundred stars have thus been taken simultaneously on a plate by a single exposure. Miscellaneous observations have been secured of the Pleiades, of the nebula in Orion, of Jupiter's satellites, and of various other objects; also of the new star in Orion, and of its spectrum, and one plate showing that this star must have been much fainter on November 9, 1885, than when discovered five weeks later.

The Prospect for Silk-Culture in the United States.—Dr. C. V. Riley, of the Entomological Division of the Agricultural Bureau, said in the preface to the second edition of his "Manual of Silk-Culture," in 1882, that the elements of successful silk-culture on a large scale were entirely wanting in this country; that "the profits of silk-culture are always so small that extensive operations by organized bodies must prove unprofitable where capital finds so many more lucrative fields for employment; that extensive silk-raising is fraught with dangers that do not beset less ambitious operations," and that silk-culture is to be recommended only as a light and pleasant employment for those members of the farmer's household who either can not do or are not engaged in otherwise remunerative work." In the latest edition of the "Manual" (1886) the author regrets that his original estimates, made in 1879, of the profitableness of the enterprise have been criticised because they had not been realized the trade had, in fact, been passing through a period of depression; and he reiterates the caution that "silk-raising on an extensive scale is fraught with so many dangers, that it is inadvisable to invest capital in such an enterprise." Silk-culture, he says in another place, "is not (and it never has been) an exceedingly profitable business; but it adds vast wealth to the nations engaged in it, for the simple reason that it can be pursued by the humblest and poorest, and requires so little outlay. The question of its establishment in the United States is, as I have elsewhere said, a question of adding to our own productive resources. There are hundreds of thousands of families in the United States to-day who would be most willing to add a few dollars to their annual income, by giving light and easy employment for a few months each year to the more aged, to the young, and especially to the women of the family, who may have no other means of profitably employing their time."

Wood and Metal for Railroad-Ties.—M. Henri Mathieu, chief-engineer of the French railway du Midi, from observations on the consumption of the wood ties on French railways, has found that their duration depends upon several factors, among which are the material employed, the climate, the ground, and the ballasting. It principally depends upon the system of preparing the ties, and the quality of the antiseptic material; and the observations made on one line often differ from those made on another line. Averaging the results—oak ties, not prepared, last fourteen years; when creosoted, eighteen years. Creosoted beech ties last from eight to ten years; creosoted