358 NATURAL THEOLOGY. 



the principle by which sky-rockets ascend in the 

 air. Of the use or practicabihty of the plan 1 am 

 not speaking; nor is it my concern to praise its 

 ingenuity; but it is certainly a contrivance. Now, 

 if naturalists are to be believed, it is exactly the 

 device which nature has made use of for the mo- 

 tion of some species of aquatic insects. The larva 

 of the dragon-^y^ according to Adams, swims by 

 ejecting water from its tail — is driven forward by 

 the reaction of water in the pool upon the cur- 

 rent issuing in a direction backward from its 

 body. 



VII. Again : Europe has lately been surprised 

 by the elevation of bodies in the air by means of 

 a balloon. The discovery consisted in finding 

 out a manageable substance, which was, bulk for 

 bulk, lighter than air ; and the application of the 

 discovery was to make a body composed of this 

 substance bear up, along with its own weight, 

 some heavier body which was attached to it. This 

 expedient, so new to us, proves to be no other 

 than what the Author of nature has employed in 

 the gossamer spider. We frequently see this spi- 

 der's thread floating in the air, and extended from 

 hedge to hedge across a road or brook of four or 

 five yards width. The animal which forms the 

 thread has no wings wherewith to fly from one 

 extremity to the other of this line, nor muscles to 

 enable it to spring or dart to so great a distance : 

 yet its Creator hath laid for it a path in the atmo- 

 sphere ; and after this manner. Though tlie ani- 



