N0\-E1IBER 1, 1892.] 



KNOWLEDGE 



209 



soda, and the ammonia taking the chlorine, forming | 

 ammonium chloride, which remains in solution. The con- 

 ditions under which the soda is produced in this method 

 of manufacture are very favourable to the formation of a 

 pure product. Both by the solution of the common salt 

 and by the subsequent crystallization of the carbonate of 

 soda, impurities are eliminated. lu the Leblauc process, 

 on the other hand, impurities accumulate, and their sub- 

 sequent removal involve time and expense. Tiie second 

 stage of the Leblanc process, as we have already stated, 

 consists in the decomposition of sulphate of soda by means 

 of limestone and coal. All these solid substances are 

 heated together on the floor of a furnace. After cooling 

 the mass is treated with water, which dissolves out the 

 carbonate of soda and leaves behind the calcium sulphide 

 and any unburnt coal. But the solution contains a good 

 many other substances besides carbonate of soda, such as 

 sodium sulphide and sodium thiocyanate, besides large 

 quantities of caustic soda. 



In spite of all disadvantages under which he suffers in 

 competition with the ammonia-soda process, the once 

 envied " Leblanc " manufacturer is still just able to 

 maintain his business by the sale of the bye-products of the 

 manufacture, made from what was formerly waste material. 

 A full account of the various inventions by which the 

 utOization of the bye-products has been brought about 

 would liU a volume, and does in fact actually till many 

 volumes of technical literature. Chemistry as an industrial 

 art is best studied in the districts where alkaU is 

 manufactured and is used for glass and soap making, in 

 South Lancashire for instance, and in the districts such 

 as the neighbourhood of ^liddlesbrough, where iron and steel 

 are made. In both districts one may study the successive 

 improvements by which the most is made of products 

 formerly considered "waste." In the lilast furnace, as was 

 pointed out in the last number of Knowledge, the 

 constant eudeavom- has been to utilize the energy of the 

 half-burnt carbon so as to diminisb the consumption of tbe 

 raw material coal. In the Leblanc process the economy 

 has been effected by the preparation of useful substances 

 from useless materials. The iron-makers, like the alkah- 

 makers, had hard times to mee.t, and they tided over the 

 hardest time by reason of the improvements which care and 

 foresight led them to introduce in the manufacture. The 

 alkali-maker only tm-ned his attention to economy of 

 material when legislation compelled him to do so ; but in 

 his case, "and in that of tbe more provident producer of iron 

 (and, we might add, of manufacturers in all branches of 

 industrial chemistry), prolonged prosperity has only been 

 attained by minimizing wastefulness as much as the 

 wasteful tendency of aU natural change permits. 



THE MOVEMENTS IN THE LINE OF SIGHT OF 

 STARS AND NEBULAE. 



By Miss A. M. Cleeke, Authoress of " The Si/stem of the 



Stills'' loid " The Histuri/ of Astronoiiii/ durhni the Nituteenth 



t-'cntunj," {(v., iVc. 



THE movements of the heavenly bodies directly to- 

 wards or from the earth might well have seemed 

 an element placed by the nature of tbings outside 

 the scope of terrestrial enquiries. Yet it has proved 

 capable of determination ; not merely in a rough : 

 and general way, but in many cases with a precision 

 answering to tbe strict demands of modern calculating | 

 astronomy. Hope has indeed been left a long way behind 

 in this branch of research, and V;7 (/«/<- niinliiw might now, 

 with full justification, be taken as then- motto by adven- 



turous astro-physicists. Through their achievements in 

 measuring spectroscopic line-displacements in stars and 

 nebulip, sidereal science is becoming rapidly revolutionized; 

 stellar systems, which might have been judged beforehand 

 of improbable, not to say impossible construction, are found 

 in full working order, and distributed with no extreme 

 scarcity through space : promise is afforded of completely 

 disentangling the translatory motion of the sun from the 

 confused flittings- of the stars ; and materials are being 

 pro\"ided for investigating their dynamical relations with 

 greatly improved prospects of success. '■' 



The theoretical possibility of spectroscopically measuring 

 motion was recognized many years before it could be realized. 

 First of all. Christian Doppler, in 1842, announced the 

 fundamental principle that light-waves are altered in re- 

 frangibility, as soimd- waves in pitch, by the recession or 

 approach of the emitting bodigs. But his use of the prin- 

 ciple was utterly futile. The cmious notion somehow laid 

 hold of him that it would account for the varied colours of 

 the stars ; as if the invisible rays at either end of every 

 ordinary stellar spectrum were not at hand to restore the 

 chromatic balance, which might otherwise be iniinitesimally 

 disturbed by motion. Alone among his contemporaries, 

 Fizeau perceived, in 1848, the real capabihties of the 

 method ; he saw that the shift of a spectrum might serve 

 to determine radial velocity, and referred to the Fraunhofer 

 lines as the natural indices to the amount of the shift. 



Nobody, however, at that time knew anything about the 

 origin of tbe Fraunhofer lines, nor was it by any means 

 certain that they possessed the essential fixity needed 

 to make their incidental displacements of critical value. 

 Fizeau's suggestion had sunk into oblivion when, after 

 twenty years, Dr. Huggins practically demonstrated its 

 importance. His success was decisive. The effectiveness 

 in sidereal investigations of the spectroscopic method of 

 determining radial motion was thenceforward generally 

 admitted, and its application became one of the recognized 

 tasks of astronomers. 



But the requisite visual observations are hampered by 

 very great difficulties. Starhght does not readily endure 

 high dispersion. Unless when concentrated by telescopes 

 of immense apertures it ceases, as it were, to be artieulate 

 if enfeebled through extension. Its characteristic rays — 

 the very objects of measurement — fade into evanescence. 

 Without high dispersion, on the other hand, their minute 

 displacements are apt to get disguised or exaggerated by 

 atmospheric tremors. Both these inconveniences can for- 

 tunately be obviated by substituting photographic for direct 



[* Miss Gierke takes a much more hopeful view of the accuracy of 

 recent determinations of motion in the line of sight than I feel that I 

 am able to take. Up to the present time there have been verr serious 

 differences in the estimates made by the best observers as to the amount 

 and even as to the direction of motion, towards or away from us, of 

 stars and nebulae. Dr. Vogel has no doubt succeeded in eliminating 

 some sources of error due to flexure of the spectroscope and other 

 causes, and it will be welcome news to all interested if his estimates 

 of the amount of his errors are conBrmed by the observations of 

 other spectroscopic observers. But at present the results inde- 

 pendently obtained in this line of research differ more from one 

 another than the determinations of parallax differ. It therefore 

 seems to me unsafe to build on such foundations when form- 

 ing conclusions as to the stellar univei'se. My remarks do not 

 apply to measures of the relative motions of adjacent stars in the 

 line of sight, such as led to the discovery by Prof. Pickering of binary 

 stars too close to be visibly separated in the largest telescopes. In 

 spite of what I have said, I feel that Miss Gierke's statement of the 

 case for Dr. Vogel is very interesting. — A. G. Eantabd.j 



[What Mr. Ranyard says in his note is undoubtedly true as regards 

 a good many of the Potsdam stars ; but the only two which have 

 been independently measured with adequate means have given 

 identical results with tliose obtained by Dr. Vogel. These are, as 

 mentioned in the article, Arcturus and Aldebaran. — A. M. Cleuee.] 



