VAPOUH. 77 



if you bury an oak, or even the whole British navy ; 

 and add but the temperature of 32, and a little point 

 of ice to a thimbleful of water, and it will cleave a 

 mountain. Although we can detect nothing, we must 

 not say dogmatically that there is nothing to be de- 

 tected ; and though we should find that the nitrogen 

 and the oxygen, together with, the carbonic acid, the 

 vapour of water, and the other ingredients, make up 

 the entire weight of the air, we may not yet be in posses- 

 sion of the whole. When the addition of 140 of heat 

 has converted a pound of ice into water, it weighs no 

 more, and it measures less ; and yet it has been changed 

 from a comparatively useless to a useful substance. If 

 the same pound of water be converted into steam at 

 the temperature of 2 12, it will not become a single 

 grain heavier ; nay, instead of pressing upon the scale at 

 all, it will have a tendency to rise in the atmosphere, or 

 to diffuse itself equally upon all sides with a force which, 

 if the vapour were in a cubical vessel, would sustain 

 a weight of about forty-eight tons, the volume being 

 augmented nearly 1700 times, and the heat absorbed 

 about 972. Here we have not only a change of state, 

 but a conversion of that which, formerly, merely pressed 

 to wards the earth's centre, with a force of a single pound, 

 into an active power, pressing upward, against gravita- 

 tion, with a force of more than one hundred thousand 

 pounds; and that, too, without any degree of heat 

 above 212, that can be detected by the thermometer. 

 If this mighty change were to take place instanta- 

 neously, the consequences would be dreadful : for the 

 moment that a cauldron boiled, there would be an ex- 

 plosion greater than the discharge of our most powerful 



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