54 



NATURE 



[March 15, 19 17 



derivation of synthetic dyes and other commercially 

 important substances from coal-tar by diagrams 

 somewhat on the lines of a genealogical table. This 

 method of demonstrating the importance of coal-tar 

 and the direct products of its distillation becomes 

 increasingly difficult each decade, because of new 

 developments which are constantly being made. 

 Messrs. G. Allen and Unwin, Ltd., are responsible 

 for the publication of one of the latest of these "coal- 

 iar charts," which was adapted by Dr. T. H. Norton 

 from a diagram originally drawn up by Dr. von 

 Brunck, the veteran director of the Badische Aniline 

 and Soda Company. In this chart the genesis of 

 many important modern dves is traced from six direct 

 or immediate coal-tar derivatives, namely, benzene, 

 toluene, the xylenes, naphthalene, phenol, and anthra- 

 cene. Among the recent additions are the substantive 

 wool dyes of the anthraquinone series, of which alizar- 

 ine saphirol may be taken as type. The direct cotton- 

 blues are valuable colours, the derivation of which 

 from tolidine and dianisidine is indicated, and refer- 

 ence is made to some of the more important chromed 

 colours. It is, however, significant of the rapidity 

 with which these charts become obsolete, that in the 

 present instance no place is found for the direct coal- 

 tar product, carbazole, and its important derived 

 colour, hydrone-blue. 



The North- East Coast Institution of Engineers and 

 Shipbuilders has just issued a standard specification 

 for cargo-steamer engines. This specification is for 

 reciprocating triple-expansion engines intended for 

 moderate-speed cargo-boats engaged in general trade, 

 and is based on the best practice of the day; the object 

 in view is the ultimate standardisation of parts. It is 

 hoped that the specification will be extended to include 

 not only the main engine proportions and scantlings, 

 but also the boilers, auxiliaries, and other detail's. 

 The council proposes that an annual revision should 

 be made in order that the specification may be kept 

 thoroughly up to date. In view of the tasks which 

 will have to be faced directly the war is over, the 

 specification and proposals are of importance, and will 

 tend to improve the organisation of our shipbuilding 

 industry in this class of vessel. 



OUR ASTRONOMICAL COLUMN. 

 Eclipse Test of Einstein's Theory of Gravita- 

 tion. — .\t the meeting of the Royal Astronomical 

 Society on March 9, the Astronomer . Royal directed 

 attention to the favourable opportunity wTiich would 

 be afforded by the total eclipse of the sun on May 28, 

 1919, for testing Einstein's predicted deflection of a 

 ray of light in passing close to the sun. The theoreti- 

 cal displacement of a star near the sun is 175" t'o/i'> 

 where r^ is the sun's radius, and r the perpen- 

 dicular distance of the ray from the sun's centre. 

 At the eclipse of June, 19 18, visible in the United States, 

 the sun will be situated in a region poor in stars, but 

 on May 28, 1919, it will be in the Hyades group. 

 There will then be thirteen stars in the vicinity of 

 the sun, of magnitudes 4-5 to 7-0, for which the 

 theoretical displacements range from 1-20" to 0-26''. 

 The greater part of the track of this eclipse will 

 unfortunately be over the Atlantic, not far from the 

 equator, but, in view of the importance of the sug- 

 gested observations, it is hoped that suitable ob- 

 serving stations may be found in Brazil or Liberia. 

 A re-examination of the photographs taken by the 

 Greenwich observers at Sfax in 1905 revealed three 

 star images, and a p>ossible fourth image involved in 

 the corona, but no trustworthy deduction as to the 

 reality of the Einstein effect could be made. These 



NO. 2472, VOL. 99] 



photographs, however, show that the standard astro- 

 graphic telescope employed is quite a suitable instru- 

 ment for the purpose in view. 



The Variable Nebula N.G.C. 2261.— Dr. V. M. 

 Slipher, director of the Lowell Observatory, has ob- 

 tained a spectrogram of Hubble 's variable nebula 

 N.G.C. 2261, to which reference has previously been 

 made in this column (Nature, vol. xc, p. 298). The 

 nebula is of cometic form, and has the irregular 

 variable star R. Monocerotis as its nucleus. The 

 nebula and star have been found to show the same 

 peculiar spectrum, consisting of a continuous spectrum 

 with bright lines or bands which are not identical 

 with those of gaseous nebulae. The observation sug- 

 gests that the nebula shines by reflected light of the 

 pulsating nucleus. Mr. Lampland has obtained two 

 direct photographs with the 40-in. reflector, one on 

 March 2, 1916, and the other on January 25, 1917, 

 showing striking differences in parts of the nebulous 

 detail. The magnitude of the apparent changes sug- 

 gests that no actual transference of matter takes 

 place, but rather that we witness the progressive 

 motion of pulses of light resulting from fluctuations 

 in the brightness of the variable star. The displace- 

 ment is estimated at 15 seconds of arc, and, assuming 

 this to be perpepdicular to the line of sight, which 

 would generally overstate the distance, the parallax 

 of the nebula would be about 000027". The corre- 

 spending distance would be 12,000 light-years. 



T 



THE CHEMICAL ENGINEER. 



HE president and council of the Faraday Society 

 are to be congratulated on their enterprise in 

 organising a very successful debate on the training 

 and work of the chemical engineer held on March 6, 

 which supplements the discussion in November last 

 on the same subject before the London section of the 

 Society of Chemical Industry. The importance of a 

 knowledge of engineering to the chemist engaged in 

 industry was accepted by all present, but the speakers 

 showed a great difference of opinion in their definition 

 of the chemical engineer. Sir George Beilby, \yho 

 initiated the discussion, considered that chemical 

 engineering has for its function the design and con- 

 struction of apparatus required for the carrying out 

 of chemical processes on a manufacturing scale. The 

 chemical engineer is a specialist who not only has at 

 his command a sound knowledge of chemical pheno- 

 mena and laws, but, more important still, he must 

 be able to see chemical problems from the chemist's 

 point of view. 



Prof. Donnan drew a distinction between research 

 chemists, engineer-chemists, and chemical engineers, 

 using the last term in the same sense as Sir George 

 Beilby. The engineer-chemist is the ordinary chemi- 

 cal student to whom a good deal of engineering 

 knowledge has been imparted, or, as Prof. Donnan 

 termed it, applied physical chemistry. He corresponds 

 to what is usually known as the plant chemist in 

 chemical industry — that is, the trained chemist who 

 has naturally mechanical aptitude and has gained 

 engineering knowledge by experience. Prof. Donnan 's 

 desire w^as to include a comprehensive training in 

 engineering in the four years' course for chemists. 

 It was suggested that some attempt should be 

 made by the teacher at the end of three years to 

 state as to what branch of chemistry a particular 

 student showed the greatest aptitude. Prof. Donnan 

 very properly laid considerable stress on the rarity of 

 the really gifted research worker, who was born 

 rather than made by training. 



Even more important in this connection was Sir 



