Peculiar Properties of Glass. 49 



I then produced a number of Rupert's drops from it by 

 melting before the blowpipe, allowing the drops to fall into 

 water and then determining the specific gravities of the 

 drops so produced, 



100 volumes of 



of original glass Equal to 



Specific became of increase of 



gravity. Rupert's drop glass. volume. 



{a) 2-451 102-073 



{b) 2-460 101-714 -h 



ic) 2-473 101-194 



One drop was made by allowing to fall into heavy 

 mineral oil, heated to 80° C, instead of cold water, a fused 

 portion of the rod. It produced a drop with one large 

 bubble in the centre. Its specific gravity was 2-4475. lOO 

 volumes, therefore, became 102-213. One drop of molten 

 glass from the rod was allowed to fall into carbon 

 tetrachloride. The liquid seemed to assume the spheroidal 

 condition around the drops, so that it remained red hot for 

 a long time under the liquid. The drop thus formed was 

 free from bubbles and its specific gravity was 2*520, thus 

 shewing that under those conditions 100 volumes of the 

 original glass contracted to 99-317 volumes. This drop 

 possessed none of the properties of the Rupert's drop, and 

 neither did the ones dropped into oil, into carbon tetra- 

 chloride, or into ether. 



The drop produced in ether had a specific gravity of 

 2-5018, whilst the original glass had a specific gravity of 

 2-4910, thus shewing that a contraction in volume had 

 resulted from the use of ether. 



To find whether glass altered in volume on being heated 

 to redness several times, I took a small piece of glass rod 

 and heated it to redness, and allowed it to cool slowly in 

 the air on three different occasions, the specific gravity 

 being taken after each heating. The following are the 

 results obtained : — 

 D 



