149 



of the other metals, of the platinum series, might be present, but they would 

 rather tend to increase its infusibility than otherwise. 



Alumina only appeared to vitrify ; while, after numerous trials with 

 crystallized quartz, I could not succeed in fusing it to a globule ; thin splinters 

 however curled round upon themselves, like scolezite, and ultimately assumed 

 a glazed appearance, clearly showing that the melting point was all but 

 reached. 



It appears from this that a very small amount of some foreign substances 

 exercises a marked effect upon the fusibility of silica, agate, opal, etc., being 

 only a little less pure than rock crystal, though so readily fusible in this 

 flame. 



Regarding the illuminating power of the flame so produced : when 

 allowed to impinge upon a solid substance such as lime or magnesia, it was not 

 only more intense (as would be expected), but the volume of incandescent 

 matter was largely increased. 



Before I proceed to urge the further use of hot air for combustions where 

 high temperatures are necessary, I wish to call attention to the fact, that the 

 temperature of the flame, which I have hitherto worked with, can be largely 

 and economically increased, by increasing that of the blast ; this can easily be 

 done to a threefold extent. 



By substituting heated hydrogen (or burnt coal gas), I have also realized 

 all the effects j ust instanced, with greater rapidity and decision ; but the 

 great diffusiveness of this gas, especially when heated, has prevented me as yet 

 carrying the experiments further. 



While on the subject of heating both combustibles (at least both the 

 substances which take part in these combustions), I cannot refrain from 

 remarking how easily the temperature of the oxy-hydrogen flame even, could 

 be increased in this manner — -the gases would of course have to be heated 

 prior to contact. Upon their more vigorous diffusiveness, when rarified, I 

 should rely for that solidity of flame, so necessary where the communication 

 of very high temperature is desired. The jets regulating the issue of the 

 gases would have to be very fine. 



Proceeding now to the next part of this subject : the result of these 

 experiments, instanced, urge me to recommend, for trial, the substitution of 

 heated air for oxygen, in most of those cases where this gas is now employed 

 in conjunction with hydrogen, or other combustible matter, as a generator of 

 heat or light : for instance, — 



1. In the metallurgy of platinum, that part of it where the metal has to 

 be fused ; also in soldering platinum stills for sulphuric acid works. 



2. The fusion of alumina in the manufacture of certain gems. 



3. In the production of the Drummond and Bude lights. 



The fusion of platinum and alumina is now effected by the oxy-hydrogen 

 flame. 



Relative to the competency of heated air to perform the part of cold 

 oxygen in the production of such intense lights as these (the Drummond and 

 the Bude), I think this can be demonstrated, almost to a certainty, in the 

 following way : 



Thus — the flame employed in these investigations has certainly a 

 minimum temperature of 4596° F., since this is the fusing point of platinum, 

 the substance most easily fused of all those I have tried, that are infusible in 

 the common flame ; doubtless the temperature is considerably higher, but I 

 will take these figures. On the other hand, the actual temperature of the lime, 

 when the Drummond light is in operation, is (on the authority of Tynclal) 

 only 2000° Cent. = 3632° F. ; hence this flame has an excess of temperature 

 over that of the incandescent lime, equal to 964° F., a pretty good margin for 



