166 Prof. Vanuxem's Experiments 



ble to the naked eye or to the microscope. The heat was 

 equally as intense in this experiment as in all the other in- 

 stances, and no condition was wanting to produce the same 

 effects, except the difference of composition. After burning 

 the lampblack for as long a time as was thought necessary to 

 make the experiment a fair one, it was again weighed, and 

 found to have lost four grammes -j-*^^^, for it weighed but two 

 grammes j^^-^. 



Five grammes of the same lampblack, heated in an open 

 platina crucible, left after its incineration one centigramme of 

 white ashes, equal to ji^ of the mass. 



From the analyses of the substances used by Professor Silli- 

 man, from which the globules were obtained, it appears that 

 they all contain foreign matter, as silex, iron, manganese, and 

 some of them also alumine; that when lampblack was used 

 which contained but j^-q of fixed impurities, no distinct glo- 

 bule or melted matter was formed, although the heat was suf- 

 ficiently great, and the combustion slow enough to admit of 

 the forming of globules, if their production was owing to the 

 fusion of carbon, and not to extraneous matter. From my 

 own experiments I always found that the more impure the 

 substance was, the more numerous and the larger were tlie 

 globules produced. 



All the globules from the different kinds of substances used 

 were readily fused by the compound flux, and underwent little 

 change when it was not used ; although the heat was, in this 

 case, of longer continuance. Matter similar to the impurities 

 discovered in the substances used was detected in them. 



From these facts it would appear, that the globules pro- 

 duced from the combustible substances operated upon did 

 not arise from the fusion of their carbon, since they can other- 

 wise be accounted for ; particularly as no experiment has been 

 made which unequivocally leads to that conclusion. The ex- 

 periment upon which Professor Silliman relies, as a proof of 

 the globules being fused carbon, is one which is not satisfac- 

 tory to me; if it had been, it would have given me great 

 pleasure, for no one, I trust, feels more interested in the sci- 

 entific prosperity of his country than I do ; and if Professor 

 Silliman were right, it would indeed be a triumph for America. 



The experiment just alluded to (see Journal of Science, 

 vol. vi. p. 347,) is the heating some of the coloured globules 

 in oxygen gas by the solar rays, with a lens. The following 

 is an extract from the papers. 



" To detach any portion of unmelted plumbago which might 

 adhere to them, I carefully rubbed them between my thumb 



and 



