Page:Popular Science Monthly Volume 19.djvu/587

Rh having this property, they are found to be composed of the carapaces of tubular diatoms, formed of rings placed one upon the other. Each grain of the sand is, in fact, a minute tube of exceedingly fine silica, forming a mineral fiber which, by virtue of capillarity, retains coloring-matters with the same force as do vegetable or animal fibers dyed under the same conditions, and that without any chemical combination having taken place, M. Engel has exhibited to the Industrial Society of Mulhouse specimens of silica colored with alizarine rose, with indigo blue, and with a deep green produced by dyeing in logwood silica colored with iron, in all of which cases the siliceous sand had been treated as if it were cotton. Other specimens showed that the same sand behaved like wool in the presence of certain coloring-matters, especially of those derived from aniline. The experiments then make known a mineral substance which has properties of physical structure analogous to those of animal and vegetable fibers that are susceptible of being dyed, the likeness being given by the minute central canal, which enables each of the microscopic tubes to absorb the coloring-matter through capillary attraction, and to fix it so that it will resist chemical agents in the same manner as do organic fibers similarly colored. "These examples," says M. Engel, "tend to prove the new fact which I have been trying to establish, that the physical structure of substances submitted to the process of dyeing is of much more importance than their chemical composition, even if it is not the only factor in the process, as my experiments make it seem probable that it is."

M. Soleillet on the Sahara.—M. Soleillet lately made a communication to a society of civil engineers on his recent journey in the Sahara. This journey, the fourth which he has made since 1872, was undertaken chiefly for the purpose of finding what products of the soil could be made to contribute to the traffic of the proposed trans-Saharan railroad. He discovered coal in the Djebel Aroun, saltpeter in the region of Ain-Sala; in his journey to the Soodan, he found the butter-tree, which has been known since the days of Park, and sent specimens of the vegetable butter to M. Thénard. This product furnishes a stearine which melts at a high temperature, and can be made to give a clear white light, and has already been employed by the English in tempering certain steels, and in oiling steam-engines. In his last journey, he discovered a plant, the Fernan, a kind of Fucus, the white juice of which takes the place of pitch with the Moors; incorporated into the wood with a hot iron, it makes an excellent calking for boats. Hoping to find in it a substitute for India-rubber, he gave some of the juice to M. Thénard, who extracted from it a substance having properties similar to those of India-rubber, except that it was not elastic. It could be perfectly vulcanized, and in that state was much like gutta-percha. An oil was extracted from it, and a resin which could be converted by heat into a beautiful and brilliant lacquer. M. Soleillet was prevented by robbers from reaching Timbuctoo, but beyond Ain-Sala he discovered a large extent of country marked by dunes running north and south, which were crossed by others running from east to west. Between these dunes were ponds of both fresh and salt water, which left, when they were dried up, rich, natural meadows. The country, having an area equal to about a quarter of that of France, possesses a healthy climate, and is inhabited by ten thousand people. Farther on is the mountainous district of Adrar, inhabited by an agricultural and commercial Berber population, with whom the Portuguese carried on an important commerce in the fifteenth century.

The Human Fossil of Schipka Cave.—A human jawbone, found in the Schipka Cave of Moravia, along with bones of the mammoth and a number of rude stone implements, exhibits, according to a description given by Professor Schaffhausen, of Bonn, some remarkable and suggestive peculiarities. It is a fragment, consisting of a fore part of the lower jaw, containing the cutting-teeth, the eye-tooth, and the two premolars of the right side. The last three teeth are still undeveloped in the jaw, but have been brought into sight by the breaking away of a part of the bone. The remarkable feature of the bone is its size. The development of the teeth is that of a child in its eighth year, while it is