H> FARADAY 



tinued applying heat to the water (as indeed happened with 

 our piece of ice here), that we did at last break up that 

 attraction which holds the liquid together, and I am about 

 to take some other (any other liquid would do, but ether 

 makes a better experiment for my purpose) in order to illus- 

 trate what will happen when this cohesion is broken up. 

 Now this liquid ether, if exposed to a very low temperature, 

 will become a solid; but if we apply heat to it, it becomes 

 vapor ; and I want to show you the enormous bulk of the sub- 

 stance in this new form: when we make ice into water, we 

 lessen its bulk ; but when we convert water into steam, we in- 

 crease it to an enormous extent. You see it is very clear that 

 as I apply heat to the liquid I diminish its attraction of co- 

 hesion ; it is now boiling, and I will set fire to the vapor, so 

 that you may be enabled to judge of the space occupied by the 

 ether in this form by the size of its flame; and you now see 

 what an enormously bulky flame I get from that small volume 

 of ether below. The heat from the spirit lamp is now being 

 consumed, not in making the ether any warmer, but in con- 

 verting it into vapor; and if I desired to catch this vapor and 

 condense it (as I could without much difficulty), I should 

 have to do the same as if I wished to convert steam into 

 water and water into ice: in either case it would be neces- 

 sary to increase the attraction of the particles by cold or 

 otherwise. So largely is the bulk occupied by the particles 

 increased by giving them this diminished attraction, that if 

 I were to take a portion of water a cubic inch in bulk (A, 

 FIG. 23), I should produce a volume of steam of that size, 

 B [1,700 cubic inches; nearly a cubic foot], so greatly is 

 the attraction of cohesion diminished by heat; and yet it 

 still remains water. You can easily imagine the conse- 

 quences which are due to this change in volume by heat 

 the mighty powers of steam and the tremendous explosions 

 which are sometimes produced by this force of water. I 

 want you now to see another experiment, which will perhaps 

 give you a better illustration of the bulk occupied by a body 

 when in the state of vapor. Here is a substance which we 

 call iodine, and I am about to submit this solid body to the 

 same kind of condition as regards heat that I did the water 

 and the other [putting a few grains of iodine into a hot 



