NATURE'S XAW OF FORCE. 249 



all examined cases agree there is at least the presump- 

 tion of a general law), the less developed that any 

 germ of life is, the greater are its powers of resistance. 

 The eggs of insects can bear a cold of 20 or 30 below 

 of Fahrenheit, indeed it has not been satisfactorily 

 proved, that any temperature that the most powerful 

 freezing mixture can produce will injure them; and 

 from analogy we should conclude, that they would be 

 more easily injured by increase of temperature, as that 

 is the means by which they are hatched ; yet we know 

 from but too frequent observation, that the eggs of the 

 common blow fly, or flesh fly (musca vomitoria), will 

 bear a heat considerably greater than that of boiling 

 water. In most we find, too, that the larva is much 

 more easily destroyed by change of temperature than 

 the egg, and the perfect animal than the larva. But 

 the excluded egg is the germ in a considerable state of 

 forwardness ; and, therefore, the analogy would lead 

 us to suppose that there is a state of the germ in the 

 ovary, in which it would be yet more difficult to injure 

 it than it is when in the egg, and which probably would 

 resist any means that we could employ for that purpose. 

 When we examine the active energy, the case is still 

 the same. An eagle could never bear the continued 

 and rapid motion that is apparent sport to a gnat ; an 

 ant will pull along a caterpillar many times its own 

 weight, through small gravel, pieces of earth, and 

 grass, which is in comparison as if a man should draw, 

 not upon wheels and along a road, but against the 

 whole friction, and through broken mountains and over- 

 turned forests, a large waggon, or an ordinarily sized 

 house. The little creature does not seem to be in the 



