24 



On the EXPANSIVE FORCE 



meet at the extremity of the diameter, which pafTes through 

 the middle of the hole. 



He found, that the iron pkig could hardly ever be driven fo 

 firmly into the fuze-hole as to refift the force of the expanfion 

 of the ice, which puflied it out with great velocity, and a bolt 

 or cylinder of ice, of a confiderable length, immediately (hot 

 up from the hole. But when the plug was fixed in with fprings, 

 which laid hold of the infide of the cavity, fo that the plug 

 could not poflibly be puflied out, the force of ejcpanfion then 

 fplit the ihell, and a fin or plate of ice fhot out quite around. 



EXTRACT from Major William's Letter, 



These experiments were made on iron-fhells, from the 

 13 inch-fliell to the coehorn, of 4.4 inches diameter, by filling 

 the fliell nearly with water, and driving in an iron plug with a 

 fledge hammer. 



REMARKS. 



Dec. 21. — The fuze-axis of the fliell lay nearly perpendicu- 

 lar to the horizon. On examining the effedl, about 9 o'clock 

 the following day, I obferved the plug gone, and a cylinder of 

 ice, of 4t inches high, rifing perpendicularly from the fuze- 

 hole, and of equal diameter. I fearched carefully for the plug, 



but 



