'EieaHy of their actual size). ( lihis last construction had the 

 -advantage of containing eight -or nme grains of carbonate, 

 whereas the ether w-ould only hold about a grain anu a half. 

 On the other. hand, it was not lit to retain a thin liquid ; but 

 •in most cases, that ckcumst.uice was of no consequence ; and 

 I foresaw Uiat the carbonate could not thus escape without 

 proving the .main point .under x.^onsideration, namely, their 

 fusion. 



The rest of the apparatus was arranged in all rcspect.s as 

 formerly described, the same precautions being taken to [de- 

 fend theplatina vessel as had been used with the inner tubes 

 .of porc'i'ain^. 



In this manner I have made a number of experiaients The results 

 duiiny this spr;ng and suaimer, the result of wiiich is hig-hly P™*'^'^ '^^'^^ 

 saLi.?iciOtory., Ihey prove, in the first place, the propriety ot bonatc is nit.r^ 

 the obs^vrvaUQQs which led to this ivhl, by shewing, that .the setVactory than 

 pure carbonate, thus defen.dsd from any contamination, is 

 decidedly more refractory than chalk ; ^since in many experi- 

 ments, the chalk has been reduced to a state of marble, 

 •while the puix; carbonate, confined in the platina vessel, has 

 been but very feebly acted upbn., having only acquired the 

 jnduration of a sandstone. 



In other experiments, however, i have been more success but the re- 



ful, having obtained some results, worthy, I thitikof the at- ^"j^'' ^^*'.'"'^ 



' t=> ' ^ ' interesting:, 



tention of this Society, and which I shall now submit to their 

 inspection. The specimens are all inclosed, for fafety, in 

 glass tubes, and supported on little stands of wax, (Fig. 31. 

 32. 33). The specimens have, in genciyal, been removed 

 from the cup or tube .of platina in which they wei'e formed, 

 the-se devices havmg the advantage of securing both the ves.sel 

 and its contents, by ejaabjiiig us to unwrap the folds without 

 violence .3 whereas, in a solid cup or tube, it would havcibeeii 

 difficult, after the experiment, to avoid the destruction either 

 ©f the vessel or jts contents, or both. 



April 1.6^ 1805. — An experiment was made with pure cal- Pure raicare- 

 careous spar from St. Gothard, rem.arkably transparent, and "veut^XrTd*'" 

 having a strong .double refraction. A temperature of 40° fusion, 

 was applied} but owing to some accident, the weight was 

 not known. The conical cup came out clean and entire, 

 IkA nt)t (] uite to the brim with a yellowish-grey substance, 

 Q 2 having 



