( 373 ) 

 I concluded thefe experiments with the 

 following : Having fufed a lava in a capa- 

 cious receiver of clay, I perforated it ob- 

 liquely fronni the top to the bottom by im- 

 merging in it a pointed iron wire three lines 

 and a half in diameter. We fhall fee in 

 Chap. XXIII. that the lavas which are moft 

 eafily fufible, and which are inflated and 

 overflow the crucible, forming a flream 

 down the fides, retain, neverthelefs, fo 

 great a tenacity in their parts, that th^y are 

 with difficulty pierced, and that the cavity 

 made by fuch perforation remains entire 

 but a very fliort time. I refolved to in- 

 troduce water into this cavity ; but as the 

 experiment was dangerous, I removed the 

 receiver from the furnace into a court-yard, 

 and poured in the water by means of a 

 long tube of iron, which reached the vefTel 

 through a hole in the door that fliut in the 

 court-yard. As foon as the w^ater entered 

 the cavity, the pieces of the receiver and of 

 the lava were forced violently to the diftance 

 of many feet, with a detonation equal to 

 the report of a mufket. 



B b 3 \yhile 



