1 lj5 ACTION ©F HEAT MODIFIED 



having a shining surfiace, with longitudinal streaks, as we 

 sometimes see on glass. This surface was here and there in- 

 terrupted by little white tufts or protuberances, disposed ir- 

 regularly. On the ledge of the cup, formed by the ends of 

 the folded platina, were several globular drops like minute 

 pearls, visible to the naked eye, the number of which amount- 

 ed to sixteen. These seem to have been formed by the en- 

 tire fusion of what carbonate happened to lie on the ledge, 

 or had been entangled amongst the extremities of the folds, 

 drawing itself together, and uniting in drops j as we see 

 when any substance melts under the blowpipe. This result 

 is preserved entire, without deranging the tube. I am sor- 

 ly to find that it has begun to fall to decay, in consequence, no 

 doubt, of too great a loss of its carbonic acid. But the glo- 

 bules do not seem as yet to have siiftered any injury. 

 Similar open- April 25. — The same spar was used, with two grains of 

 water, and a heat of 35°. I have reason to suspect, however, 

 that, in this and several other experim.ents made at thi3 time, 

 the metal into which the cradle was plunged, on first intro- 

 duction into the barrel, had been too hot, so as to drive off the 

 water. There was a loss of 6 A per cent. The result lay in 

 the cup without any appearance of fVothing or swelling. 

 The surface was of a clean white, but rough, having in one 

 corner a space shining like glass. The cup being unwrapt, 

 the substance was obtained sound and entire : where it had 

 moulded itself on the platina, it had a small degree of lustre, 

 with the irregular semitransparency of saline marble : when 

 broken, it preserved that character more completely than in 

 any result hitherto obtained ; the fracture being very irregu-. 

 lar and angular, and shining .with facettes in various direc- 

 tions. I much regret that this beautiful specimen no longer 

 exists, having crumbled entirely to pieces, notwithstanding all 

 the care I took to enclose it with glass and wax. 

 C'i^rbonate of April 26. — An experiment was made with some carbonate 

 Jimepnrificdby of W^q.^ purified by my friend Sir George Mackenzie. Two 

 artwas rerder- . / • , j j i . i .. t l ■ 



eA oiystalline grains of water were introduced, but were lost, I suspect, as m 



and semitran?- the, last case. The heat applied was 32". The loss of weight 



0/32". ^^ *^^ "W2S 10.() per cent. Yet though made but one d;iy after the 



last-mentioned specimen, it remains as fresh and entire as at 



■irst and promises to continue unchanged. The external 



surface. 



