Page:Popular Science Monthly Volume 59.djvu/520

510 flame, becoming plastic enough for manipulation only above the melting point of platinum. In preparing tubes the first step is a rod, which is made by fusing small pieces of silica together, one after another. This rough rod is then re-heated and drawn out into finer rods about a millimeter in diameter. These rods are then bound around a thick platinum wire and heated till they adhere to each other forming a tube which can then be drawn out and worked much as a tube of glass. By blowing a small bulb on the end of the tube, surrounding it with a ring of silica, re-heating and blowing, the tube can be lengthened or the bulb enlarged at will. From this starting point it is possible to make quite complicated apparatus.

An examination of vitrified silica reveals several properties which give it a peculiar value for many purposes. Its melting point is so high that a platinum wire imbedded in a thick silica tube can be fused so as to flow out, before the tube softens sufficiently to lose its shape. Its coefficient of expansion is far less than that of any similar substance, being only one-seventeenth that of platinum. This expansion is very regular up to 1,000°, when it diminishes rapidly up to 1,200° and from this point on it contracts. Up to 1,500° it remains practically solid. In its expansion it differs very markedly from quartz, which not only has a much higher coefficient of expansion, but which at 570° expands so rapidly that it is shattered. A rod of vitrified silica can be heated white hot and then immediately plunged into liquid air without suffering injury, indeed it gains in elasticity when thus treated. These properties promise to be of great value in the construction of thermometers. Its transparency to the ultra-violet rays of the spectrum will give it a decided advantage over glass in spectroscopic work. It is also interesting to note that tubes of silica can be heated sufficiently high for nitrogen and oxygen to unite directly on passing through them. It is, on the other hand, slightly permeable to hydrogen at a temperature of 1,000°C. Altogether vitrified silica offers an interesting field of development in the immediate future.

following paragraph is reproduced from the 'Electrical World,' as a favorable occasion for two remarks that it has for some time seemed desirable to make:

In the current number of our esteemed contemporary, the which is, alas! more popular than scientific in the single particular that its pages lie largely sealed from mortal eye until separated by that anachronous atrocity—the paperknife—appears a delightful article by Professor J. J. Thomson, 'On Bodies Smaller than Atoms,' an abstract of which appears in the Digest. It is a commentary upon the spread of technical education that a paper on this most abstruse subject, and actually containing some little algebra, should find the light of day in popularized literature, and awake a gleam of recognition from the eyes of many who are not scientists. Twenty years ago such an article on such a subject would have lain on popular benches as caviare to the multitude. It is difficult to say which commands our admiration the more—the article itself, or the fact that the great world should be capable of admitting it into semi-popular literature. Either consideration presents a triumph, the one over inanimate, the other animate, nature.

The first remark concerns trimming the pages of the It appears from the correspondence of the publication department that to trim or not to trim is a burning question. An 'anachronous atrocity' is pretty strong language, but it seems to define a widespread creed. Some people apparently do not know that there is a good scientific reason for not trimming the edges, namely, that a magazine or book that has been trimmed cannot be ; properly bound afterwards.