Infects of Heat modified ly Compression. 149 



.and distinctly rounded air-holes. The fragments of shell, 

 which had occupied the upper part of the little tube, had 

 lost every trace of their original shape in the act of ebulli- 

 tion and fusion. 



No. 7. — On the 2<3th a similar experiment was made, in 

 which the barrel was thrown open, in spite or' this pow erful 

 compressing force, with a report like that of a e;un (as I was 

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

 state of strong vibration. The carbonate was calcined, and 

 somewhat frothy; the heart of one piece of chalk used was 

 in a state of saline marble. 



It now occurred to me to work with a compressing force, 

 and no air-tube, trusting, as happened accidentally in one 

 case, that the expansion of the liquid would clear itself by 

 gentle exudation, without injury to the carbonate. In this 

 mode it was necessary, for reasons lately 6tated, to place 

 the muzzle upwards. Various trials made thus, at this 

 time, afforded no remarkable results. But I resumed the 

 method, with the following alteration in the application of 

 the weight, on the 27th of April 1804, 



I conceived that some inconvenience might arise from the 

 mode of em ploying the weight in the former experiments. 

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

 effect propagated along it, so as to press against the barrel at 

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

 of motion in this way requiring some sensible time, a con- 

 siderable quantity of carbonic acid might escape, by a sudden 

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

 fore thought that more effectual work might be done by 

 placing a heavy mass (fig. 40) so as to act directly and 

 simply upon the muzzle of the barrel ; this mass being 

 guided and commanded by means of a powerful lever {ah). 

 For this purpose I procured an iron roller, weighing 3 cwt. 

 7 lbs., and suspended it over the furnace to the end of a 

 beam of wood, resting on a support near the furnace, with 

 a long arm guided by a rope (cc) and pulley (d), by which 

 the weight could be raised or let down at pleasure. 



With this apparatus I made some tolerable experiments; 



tmt I found the weight too light to afford certain and steady 



K 3 results 



