PRINCE RUPERT'S DROPS. 45 



when I tell you that this piece of common 

 charcoal is just the same thing, only differently 

 coalesced, as the diamonds which you wear? 

 (I have put a specimen outside of a piece of 

 straw which was charred in a particular way 

 it is just like black lead.) Now, this charred 

 straw, this charcoal, and these diamonds, are 

 all of them the same substance, changed but in 

 their properties as respects the force of cohesion. 

 Here is a piece of glass [producing a piece of 

 plate glass about two inches square], (I shall 

 want this afterwards to look to and examine its 

 internal condition) and here is some of the 

 , same sort of glass differing only in its power 

 of cohesion, because while yet melted it has been 

 dropped into cold water [exhibiting a "Prince 

 Eupert's drop( 10 ) {fig. 13)], and if I take one 

 of these little tear-like pieces and break off 

 ever so little from the point, the whole will at 

 once burst and fall to pieces. I will now break 

 off apiece of this. [The Lecturer nipped off a 

 small piece from the end of one of the Eupert's 

 drops, whereupon the whole immediately fell 

 to pieces.] There! you see the solid glass has 

 suddenly become powder, and more than that, 

 it has knocked a hole in the glass vessel in 



