CONSTITUENT MATERIALS OF THE EARTH. 17 



distant than Sirius, as within the bounds of our own solar 

 system or our own globe. 



Matter, whether it consists of about fifty-five ingredients, 

 or only one, is liable to infinite varieties of condition under 

 different influences. As a familiar illustration, water, when 

 subjected to a temperature under 32 Fahrenheit, becomes 

 ice ; raise the temperature to 212, and it becomes steam, oc- 

 cupying a vast deal more space than it formerly did. The 

 gases, when subjected to pressure, become liquids ; for ex- 

 ample, carbonic acid gas, when subjected to weight equal to 

 a column of water 1230 feet high, at a temperature of 32, 

 takes this form : the other gases require various amounts of 

 pressure for this transformation, but all appear to be liable to 

 it when the pressure proper in each case is administered. 

 Heat is a power greatly concerned in regulating the volume 

 and other conditions of matter. The chemist will probably 

 yet tell us what additional amount of heat would be required 

 to vaporize all the water of our globe ; how much more to 

 disengage the oxygen which is diffused in nearly a proportion 

 of one-half throughout its solids ; and, finally, how much 

 more would be required to cause the whole to become vapori- 

 form, which we may consider as equivalent to its being re- 

 stored to its supposed original nebulous state. He may 

 calculate with equal certainty, what would be the effect of a 

 considerable diminution of the earth's temperature what 

 changes would take place in each of its component sub- 

 stances, and how much the whole would shrink in bulk. 



The earth and all its various substances have at present a 

 certain volume in consequence of the temperature which 

 actually exists. If, then, we admit that its matter and that 

 of the associate planets was at one time diffused throughout 

 the whole space now circumscribed by the orbit of Uranus, it 

 follows, after what we know of the power of heat, that the 

 nebulous form of matter was attended by the condition of a 

 very high temperature. The nebulous matter of space, pre- 

 viously to the formation of stellar and planetary bodies, must 

 have been a universal Fire Mist, an idea which we can 

 scarcely comprehend. The formation of systems out of this 



