x^6 EFFECTS of HEAT 



held tight by the beam, but was rent and a little fwelled 

 at the breech. The rent was wide, and fuch as has always 

 appeared in the ftrongeft barrels when they failed. The car- 

 bonate was quite calcined, it had boiled over the little tube, 

 and was entirely in a frothy ftate, with large and diftinctly 

 rounded air-holes. The fragments of fhell which had occupied 

 the upper part of the little tube, had loft every trace of their 

 original fhape in the act of ebullition and fufion. 



No. 7. — On the 26th a fimilar experiment was made, in 

 which the barrel was thrown open, in fpite of this powerful 

 comprelling force, with a report like that of a gun, (as I was 

 told, not having been prefent), and the bar was found in a 

 ftate of ftrong vibration. The carbonate was calcined, and 

 fomewhat frothy, the heart of one piece of chalk ufed was in 

 a ftate of faline marble. 



It now occurred to me to work with a comprefling force, and 

 no air-tube, trufting, as happened accidentally in one cafe, that 

 the expanfion of the liquid would clear itfelf by gentle exu- 

 dation, without injury to the carbonate. In this mode, it 

 was necefTary, for reafons lately ftated, to place the muzzle 

 upwards. Various trials made thus, at this time, afforded no 

 remarkable refults. But I refumed the method, with the fol- 

 lowing alteration in the application of the weight, on the 27th 

 of April 1804. 



I conceived that fome inconvenience might arife from the 

 mode of employing the weight in the former experiments. 

 In them it had been applied at the end of the bar, and its 

 effect propagated along it, fo as to prefs againft the barrel 

 at its other extremity. It occurred to me, that the propagation 

 of motion in this way, requiring fome fenfible time, a confi- 

 derable quantity of carbonic acid might efcape by a fudden 

 eruption, before that propagation had taken effect. I there- 

 fore thought, that more effectual work might be done, by 



placing 



