50 Mr. W. Thomson on the 



Specific gravity of original glass 2*4954 



After first heating 2-4964 



„ second „ 2-4981 



„ third „ 2-4986 



The same glass was then fused and dropped 

 into cold mineral oil, and its specific 



gravity was 2-4694 



The drop in oil contained vacuous spaces or bubbles, but 

 the drops formed in carbon tetra-chloride, chloroform, or 

 ether, were all free from vacuous spaces. The drop in 

 water ceased to shew red-hot after i to 2 seconds, whilst in 

 ether it remained red hot for 5 to 6 seconds, and in air for 

 about 20 seconds. 



I placed a Rupert's drop in hydrofluoric acid till all the 

 outer skin was removed ; when the tail was then broken the 

 drop remained intact, and it was not till the thick part of 

 the drop was broken in a vice that the whole drop broke 

 into pieces, but the pieces into which it broke were much 

 larger than when broken in the usual manner. 



A small drop was placed in hydrofluoric acid, and, after 

 a certain amount of the skin had been dissolved, an even 

 layer of about iVth of an inch was found broken into small 

 pieces equally all round the drop, these pieces remaining 

 in situ, and could be easily removed by the fingers, whilst 

 a bead of glass which formed the core came out clear and 

 transparent, and when this was broken in a vice it did not 

 break throughout into small pieces, but acted like an ordi- 

 nary piece of glass. 



Two drops were taken, one was 

 dipped in molten paraffin, so that 

 the part from the line A, shewn in 

 A the figure, to the point was coated 



with paraffin, the other was dipped 

 so that the part from the line A 

 to the bottom was thus coated. 



