102 



KNOWLEDGE. 



[Mat 1, 1899. 



A nation which spends annually enormous sums upon 

 education might well spend an adequate fraction on the 

 suppression of this style of thing. 



A certain " Mother Shipton " is credited with the 

 " prophecy " that " one day carriages should run without 

 horses," or something to that effect. Should that Delphic 

 utterance have entitled her, in her own time, to any credit 

 as a discoverer, as an inventor, or as a scientist ? Emphati- 

 cally, no ! Yet, not to deprive her of all credit, one may 

 say. without reserve, that she made a shrewd remark. 



But there is such a thing as scientific speculation, which 

 may be indulged in with great benefit, both to the actual 

 speculator and those to whom he communicates his ideas. 

 Workers in every branch of science can multiply instances 

 of such rational speculation which have indicated most 

 profitable lines for investigation. In this connection, the 

 chemist might possibly refer to Mendelejeff, the astronomer 

 to GallUeo, and the electrician to Grey or t'romwell Varley. 



It will be noted that, so far as electrical workers are 

 concerned, two names are mentioned. Apart from the 

 fact that this is perhaps natural in a paper under the 

 above heading, there is a specific point which I would 

 bring out here. Stephen Grey expressed a hope — to 

 which reference has already been made — while Varley 

 uttered a warning, concerning the speed of signalling 

 which could be attained through a submarine cable. Thus 

 while both indulged in well-founded scientific speculation, 

 and both had the ultimate advancement of science in 

 view, the one encouraged, and the other strove to damp 

 the ardour of his contemporaries. 



Many other instances might be quoted, but surely these 

 names will more than serve. 



Another form of hysteria, perhaps as pernicious as that 

 already mentioned, has recently led certain really intelligent 

 scientists to announce (with what one can only allude to as 

 a flourish of trumpets) what they are about to do. On the 

 other band, if it is not they themselves who have made such 

 statements, they have the option of either contradicting 

 them, or stating that they are made without authority. It 

 is in a great measure due to this hysterical tendency that 

 we hear of the internal troubles of scientific societies. A 

 painful controversy is raging now, and the long established 

 constitution of the society appears to be threatened. 



But perhaps too much has already been said on this 

 subject. Finally, it may be urged that electricity can add 

 to the foundation of its claim to be an exact science the 

 plain statement that, even when arbitrary assumptions are 

 made and arbitrary expressions are used, a distinctly 

 scientific convention is always adopted, and, the position 

 being so well understood, there is absolutely no danger of 

 serious error being allowed to creep in on account of either 

 such expressions or such assumptions. 



As regards scientific speculation which can be justified, 

 electricians can point to their share ; but, alas ! it must 

 be admitted that we suffer to far too great an extent from 

 hysteria, both internally and externally. The internal 

 suffering is by far the most acute. We can only hope that 

 the external trouble, thrust upon us and the public, is not 

 to be allowed to become chronic. 



THE ACETYLENE INDUSTRY.-II. 



By George T. Holloway, assoc.k.coll.sc, f.i.c. 



IT would be impossible within the limits of this article 

 to describe the various generators which have been 

 used or patented for the production of acetylene 

 from calcium carbide, but the general types may be 

 briefly referred to. Those shown at the Exhibition of 

 the Imperial Institute during last summer were divided 



into three groups — (1) those in which the gas is generated 

 by the action of water dripping or flowing in a small 

 stream upon the carbide; (2) those in which water rises 

 around the carbide ; and (3) those in which the carbide 

 falls into water. 



In Class 1, the water commonly falls upon the carbide 

 from perforations in a metal pipe, while in Class 2 the 

 water is usually allowed to pass on to or through the 

 carbide, which is contained in perforated trays. This 

 latter arrangement is frequently made automatic, by the 

 carbide being contained in a receptacle fixed to an inner 

 vessel which rises and falls as the gas is generated and 

 used op, as in the case of a gasometer, so that the carbide 

 is raised out of the water or lowered into it, as the gas is 

 produced or consumed. A common form for Class '6 con- 

 sists of a generator having a aide shoot through which the 

 carbide is dropped into the water as required. 



A lengthy series of experiments made by Prof. Vivian 

 B. Lewes as to the temperatures developed by the reaction 

 between the carbide and the water under these various 

 conditions, and as to the amount of gas produced, and 

 other matters connected with the application of acetylene, 

 especially for small lighting installations, has resulted in 

 some interesting conclusions. In each of the first two 

 forms there is a considerable liability to such a rise of 

 temperature as leads to polymerization, and also to the 

 partial decomposition of the gas, with production of tar, 

 benzene, and other bodies, which not only reduce the 

 volume of acetylene generated, but also tend to choke up 

 the burner, as described later on. The second class of 

 generator, which constitutes the bulk of those on the 

 market, is found to be less objectionable than the first 

 form, but those of the third class, of which very few are 

 in use, appear to be the most scientific, and give rise to 

 less over-heating, although it has been stated that their 

 yield of gas is below that of the other forms. 



After the rapid evolution of gas which occurs on the 

 first admixture of the carbide with water, a slow evolution 

 continues for some time, and for this reason, in apparatus 

 having an automatic " cut-ofi'," the arrangements should 

 be such that the cut-oft' acts when the gas-holder is not 

 more than three-fourths charged. Finally, a large excess 

 of water must be used to minimize overheating of the 

 carbide, and a cock should be fitted at the base of the 

 generator to draw off the lime sludge formed daring the 

 reaction. 



The danger of explosion from acetylene gas may be 

 attributed to (1) the action of the acetylene on the metal 

 used in the construction of the gas-holder and its fittings, 

 with production of explosive acetylides; (2) to the presence 

 of phosphoretted and siliciuretted hydrogen and, perhaps, 

 other impurities, and (3) to the endothermic nature of 

 acetylene. Other and unknown causes appear also to 

 form factors in this problem. 



The presence of phosphoretted and siliciuretted hydrogen 

 in acetylene is due to impurities in the carbide. Prof. 

 Lewes has found from a trace to 2-3 per cent, of the former 

 gas (an average of 0-65 per cent, on twelve samples) in 

 acetylene, but not more than very small traces of silici- 

 uretted hydrogen were detected, and his experiments tend 

 to show that in carbide of English manufacture there is no 

 danger of explosion from the presence of either of these 

 gases, provided the generator is so constructed as to 

 prevent overheating of the carbide. It appears, however, 

 according to Dr. Grainger, that friction, even such as may 

 be produced by opening a valve, is sufficient in the case of 

 the liquefied gas to sometimes induce an explosion. 



Other impurities, such as ammonia, sulphuretted hydro- 

 gen, arseniuretted hydrogen, marsh gas, oxygen, nitrogen, 



