COMBINATION OF WATER. 301 



Water, from the consideration of which a digression 

 has been indulged in, to consider the curious character 

 of one of its elements, water is one of the most 

 powerful chemical agents, having a most extensive 

 range of affinities, entering directly into the composition 

 of a great many crystallizable bodies and organic com- 

 pounds. In those cases where it is not combined as 

 water, its elements often exist in the proportions in 

 which water is formed. Gum, starch, and sugar, only 

 differ from each other in the proportions in which the 

 elements of water are combined with the carbon. 



In saline combinations, and also in many organic 

 forms, we must regard the water as condensed to the 

 solid form ; that is, to exist as ice. We well know that, 

 by the abstraction of heat, this condition is produced ; 

 but, in chemical combinations, this change must be the 

 result of the mechanical force exerted by the power of 

 the agency directing affinity. 



In the case of water passing from a liquid to a solid 

 state, we have a most beautiful exemplification of the 

 perfection of natural operations. Water conducts heat 

 downwards but very slowly ; a mass of ice will remain 

 undissolved but a few inches under water, on the surface 

 of which, ether, or any other inflammable body, is 

 burning. If ice (solid water) swam beneath the surface, 

 the summer sun would scarcely have power to thaw it ; 

 and thus our lakes and seas would be gradually con- 

 verted into solid masses at our ordinary winter tem- 

 peratures. 



All similar bodies contract equally during the pro- 

 cess of cooling, from the highest to the lowest points to 

 which the experiments have been carried. It has been 

 thought that if this applied to water, the result would be 

 the sudden consolidation of the whole mass. A modi- 

 fication of the law has been supposed to take place to 

 suit the peculiar circumstances of water. Nature 

 never modifies a law for a particular purpose ; we must, 



