Rensselaer Union, Volume 8, Number 4, Rensselaer, Jasper County, 14 October 1875 — MECHANICAL AND SCIENTIFIC. [ARTICLE]

MECHANICAL AND SCIENTIFIC.

—All that glitters is not gold ; nor is all the iron called Swedish made in Sweden.. —A very’ interesting exhibition has been made befege the British Association of Science, consisting of a series of fourteen . carefully-constructed thermometers'differing either in the size or shape of the bulbs or in the material with which they were filled, some being, mercurial and others containing alcohol, and all being made in the most perfect manner in respect both to the scientific principle and the mechanism involved. As the result of experiments made with these various instruments, under the same circumstances of temperature and position, it was ascertained that very large mercurial bulbs are but little better than those of the same size filled with alcohol, but that with small bulbs the mercury is much more sensitive.i —The peculiar phenomenon of the variability of the'spectra of glowing gases has been -investigated by a German chemist, who finds that this is affected by the following circumstances, namely: The density .of the gas; the strength of the galvanic current that heats it, as well as the method of electric discharge, and the changes of temperature that are produced thereby; the thickness of the glowing stratum of gas; and, finally, the chemical purity of the gas. With regard to the density of the gas, it is found that the diminution of density causes the spectrum to become fainter and fainter, and leads to a change in the relative position of certain of the bright lines, which sometimes will become broad bands. When the highest possible degree of rarefaction is realized, it is found that the bandsrespectively'become groups of well-defined lines that are occasionally merged into each other .—Chicago Tribune. —The atmosphere of Venus is now a subject that is receiving universal attention from astronomers. It is known that many of the observers of the transit stations, last December, described a beautiful phenomenon that occurred as the plan,et slowly made its way over the sun’s disc. A pale circle of white light was distinctly visible around a portion of the planet’s edge, differing entirely from the brilliant sunlight, but closely resembling the soft light of the moon. This ring of pale light is supposed to be the atmosphere surrounding the planet, and, in the opin* ion of many astronomers, it is much deeper than the atmosphere of the earth. Other observers, however, reject this theory', and regard the phenomenon as in some mysterious way connected with the sun’s eorona. The transit to occur seven years hence may possibly throw light upon this problem as well as upon some other related astronomical questions. —Brooklyn Eagle. —The combination signal and flashlight is coining into extensive use. its value consisting in its convenient adaptation as a danger or telegraphic signal, always ready and at hand in case of accidents, alarms, fogs, or threatened collisions, it being also a powerful illuminator in dark nights, rendering the smallest objects visible for many yards distant in all directions. It is an ordinary lantern, in which lard or sperm-oii is used, with a separate reservoir containing naphtha or volatile oil held in suspension by cotton batting, packed in a wire-gauze sack. By means of a cylinder, or air-tube, passing through the reservoir, common air is injected, forming, with the volatile oil, hydro-car-bon gas, that escapes through a tube adjoining the fixed light, thus creating a brilliant flame a foot or more in length. The apparatus is an improvement on sig-nal-lanterns for railroads, its effect as a signal flash-light being perfect.— N. Y. Sun.