484 



NATURE 



[August i6, 191 7 



are dealt with in chaps, v. to x. The work done 

 on vanes, and water-wheels and turbines take up 

 the following three chaipters, and the book closes 

 with chapters on naval hydromechanics, pumps 

 and pumping. The space devoted to the flow of 

 water is large by comparison, and includes, in 

 addition to the usual subjects, the flow through 

 fire-hose 'and in fountains. Biel's formula for the 

 flow in pipes and channels is discussed, and results 

 calculated from it are compared with those given 

 by Kutter's formula. The treatment of this section 

 is adequate and good. 



The book contains many illustrations, mostly 

 outline diagrams, and while these illustrate very 

 well the principles discussed, the inclusion of a 

 larger number of working drawings would have 

 been better. This remark applies particularly 

 to the sections dealing respectively with turbines 

 and pumps ; the latter has no working drawings 

 whatever, and both sections could bear consider- 

 able expansion. Hydraulic machinery is dismissed 

 in three and a half pages, with four inadequate 

 sketches, regarded from the point of view of the 

 student who desires to know how the appliances 

 are actually constructed. 



Throughout the entire volume there are copious 

 references to articles in periodicals, other books, 

 transactions of societies, etc. 



LETTERS TO THE EDITOR. 

 [The Editor does not hold himself responsible for 

 opinions expressed hy his correspondents. Neither 

 can he undertake to return, or to correspond with 

 the writers of, rejected manuscripts intended for 

 this or any other part of Nature. No notice t.« 

 taken of anonymous communications.] 



A Plea for the Fuller Utilisation of Coal. 



The suggestion In your article of July 26 on the 

 Fuel Research Board of *' the employment of coke- 

 oven gas to supplement the output of suitably situated 

 gas works, and the more extended use of water-gas," 

 is timely, and it certainly does not err on the side 

 of excess. 



' As pointed out in a paper which I read before 

 Section G of the British Association in 1906^^ " if 

 all the foundry coke which is used in this country 

 were made in by-product recovery ovens, the resulting 

 yield of gas would be more than 160,000,000,000 

 cub. ft. per annum, or more than is used in one year 

 in the whole of the United Kingdom^' ; and, as 

 regards the distance to which the gas might be con- 

 veyed, it is scarcely an exaggeration to say that the 

 economic limit of supply is the coast-line of Great 

 Britain. 



The possibility of conveying gas over long distances 

 is scarcely realised in this country, although in 

 the United States gas has for many years past been 

 piped at high pressures over hundreds of miles. 



The need for a cheap suppiv of power is beginning 

 to make itself felt. Not unnaturally we turn to 

 electricity ; but over long distances gas is a very 

 formidable competitor. 



The question of fertilisers is also attracting atten- 

 tion. For years past we have been spending some- 

 thing like i5,ooo,oooL per annum on importing nitrate 

 of soda from Chile, and wasting an equival&nt 

 amount of nitrogen Jsy our primitive methods of 

 using coal. 



We are beginning, too, to realise the importance 

 NO. 2494, VOL. 99] 



of the great coal-tar industry which we have allowed 

 to slip into German hands. 



In every direction we are confronted by problems 

 which depend for their solution on a fuller utilisa- 

 tion of our great national asset. 



The burning of coal in its raw state was long ago 

 denounced by the late Sir William Siemens as " a 

 barbarous practice"; but habit is strong, and our 

 business men have been too busy making monev to 

 give much thought to economy in power production. 



Recent events have violently jolted us out of our 

 ancient grooves, and there is now a disposition to 

 consider novel proposals on their merits. 



I showed in a paper read before the Society of 

 Arts in March, 1906, that coal-gas made at the pit's 

 mouth could be delivered in London at a price at 

 which it would oust coal from the home and from 

 many industrial processes. My proposals may be 

 briefly summarised as follows : — 



(i) The whole of the coke-oven gas now wasted 

 would be utilised, and a part of the additional gas 

 required generated from small coal at the pit's mouth 

 by the ordinary method of carbonisation, but with- 

 out regard to illuminating power. 



(2) The waste heat from the retorts would be 

 utilised to raise steam for compressing the gas. 



(3) The exhaust steam would be used to generate 

 water-gas. 



. (4) The gas would be piped to wherever required,, 

 and delivered under sufficient pressure to^ charge the 

 storage cylinders of motor vehicles. 



(5) Chemical works would be established near the 

 collieries to deal with the ammonia, tar, etc. 



In this way practically the whole of the available 

 heat of the coal would be turned to account, instead 

 of wasting some 90 per cent, of it, as is done in 

 generating electricity by steam-|power ; and the 

 residuals, the whole of which are wasted when coal 

 is burnt under a boiler, would be turned to good 

 account. 



The question bristles witii points of scientific in- 

 terest, but I have already trespassed long enough 

 on your space and on the patience of your readers. 



, Arthur J. Martin. 



University Hall, Carlyle Square, 

 Chelsea, S.W.3. 



Devitrification of Quartz Glass. 



In an article by Audley, published in the Transactions 

 of the Ceramic Society, vol. xvi., part i., p. 124, it is 

 stated that the addition of zirconia to fused quartz 

 gives a product resembling quartz opaque glass, but 

 in man}- respects superior to quartz glass, and less 

 easily devitrified. 



The statement is repeated in the article on the uses 

 of zirconia in the issue of Nature of July 5, and had 

 previously found its way into much of the literature 

 dealing with quartz glass. The alleged superiority of 

 quartz glasses containing zirconium or titanium oxides 

 is due to some experiments carried out by Thomas in 

 the laboratory of Borchers at Aachen, and published in 

 the Chemiker Zcititng in 1912. These experiments 

 were shown by me {Chem. Zeit., 1913, p. 589), and 

 independently by others, to be untrustworthv, quartz 

 glasses containing zirconium and titanium oxides being, 

 in fact, more liable to devitrifi nation than quartz glass 

 prepared from pure silica. The purer the quartz glass 

 is the less is its tendency to devitrify after prolonged 

 exposure to heat. Quartz glass manufacturers in this 

 country are well aware of tliis, and endeavour to pro- 

 duce a material as free as possible from all impurities. 



A. C. MiCHIE. 



The Wallsend Laboratories, 



Wallsend-on-Tyne, August 7. 



