DISCOVERY 



211 



the failure of his successors, and the praise of him b}' 

 the great Southern antagonist, Lee, settle the point. 

 Soldiers, naturallj- sjTnpathising with an unfortunate 

 commander, complain, on the other hand, that Lincoln 

 did not give McLellan a fair chance. Three points in 

 the controversy may suffice. First, Lincoln, though 

 rightly yielding his judgment to McLellan's, long 

 pressed him to advance due south against Johnston's 

 forces near \\'ashington. ^^'e now have Johnston's 

 own account of his position, and it is decisive for 

 Lincoln. Secondly, when McLellan was carrying out 

 his own plan of attacking Richmond from a sea base 

 lying south-west of it, Lincoln withheld certain forces 

 from him. Now, it is incontestable that McLellan's 

 demands would not, on his own showing, have left 

 Washington sufficiently protected, that the loss of 

 Washington would have been a deadly blow to the North 

 at that time, and the loss of Richmond would have been 

 but a sUght blow to the South. Thirdly, when McLellan 

 had been superseded, but reinstated in command after 

 the disastrous failure of his successor had resulted in 

 an invasion of the North, and when he had warded off 

 that blow but failed to follow up his success, Lincoln 

 abruptly and finalh' removed him. It is now at last 

 known that, when Lincoln did this, he had received 

 trustworthy information that McLeUan was in treaty 

 with pacifists in the North to let the South down easily, 

 in consideration of their support for the Presidency. 

 These are tiresome matters, but they show that at 

 point after point Lincoln acted rightly where he had 

 been obviously wrong, and we may accept it that 

 this inexperienced man proved a strong administrator 

 before we proceed to consider whether he was an en- 

 Ughtened statesman. 



{To be concluded next month.) 



Some Aspects of Carbide 



in the Light of Recent 



Discoveries 



By Edward Gahen, A.R.G.Sc, F.I.G. 



The average cychst or motorist who buys a tin of 

 carbide never gives it a further thought. He just fills 

 up his lamps, and there the matter rests. He does not 

 ask what the stuff is, how it is -made, or of what 

 materials it is composed. And yet, if he only knew, 

 the whole hfe -history of carbide is one of absorbing 

 interest. Everybody to-daj- knows all about coal-tar 

 and the marvels the chemist has effected with this 



apparently valueless and messy material : coal-tar 

 colours are the commonplace of every exhibition ; but 

 one never hears anything about another waste-product 

 of the gas-works, the coke that is left behind in the 

 retorts after the gas has been distilled off with the tar 

 and the ammonia. Now, it is from this coke, together 

 with another very common substance, ordinary quick- 

 lime, that the carbide is made. To-day, for one nation 

 to wage w-ar on another with any chance of success, 

 that nation must be possessed of sufficient supplies of 

 at least three absolutely essential materials — nitrates, 

 acetone, and tungsten — to say nothing of armies of 

 men to make use of the products provided by the 

 ingenuity of the chemists and metallurgists. Under 

 the circumstances, it seems almost incredible that 

 Great Britain went to war in the cause of right without 

 assured suppUes of any one of them, though it must 

 be admitted that our Navy made it tolerably certain 

 that we should be able to get nitrates across from 

 Chile in quantities large enough to meet our every 

 demand. Now, of the three substances of such para- 

 mount importance, two are directly capable of being 

 obtained from carbide. It is for this reason that this 

 material has assumed an importance which it has 

 never held before. 



The credit of first preparing carbide must be ac- 

 corded to Woehler, a German chemist of renown, 

 who in 1862 succeeded in making very small quan- 

 tities of this material by a very lengthy and some- 

 what costly process, and at the same time he showed 

 that it gave rise to a gas when it was moistened 

 with water. Calcium carbide and the resultant gas, 

 acetylene, however, remained mere chemical curiosities 

 for another thirty years ; and it was not till after the 

 discovery and development of the electric furnace 

 that carbide was manufactured on a commercial scale, 

 and even then more or less as the result of an accident, 

 Thomas L. \Mlson was experimenting with the electric 

 furnace, trying to get metaUic calcium by heating 

 carbon and lime together. On tapping the furnace, 

 he found that he had a dark-coloured liquid mass, 

 which on cooling solidified to a brittle crystalline 

 solid. Now, if calcium had been formed on dropping 

 this solid into water, hydrogen gas should have been 

 given off ; when this was tried, however, a gas came 

 off which certainly was not hydrogen, for it burnt with 

 a bright, smoky flame very unlike the flame of hydrogen, 

 which is very nearly colourless. This new substance 

 was calcium carbide, the same as Woehler had prepared 

 so many years before. From such small beginnings, 

 one discovery leading to another, this experiment led 

 to unexpected developments. 



When lime is heated with coke to the great tem- 

 peratures now so easily attained with the modern 

 electric furnace, combination takes place, with the 



