OF INSECTS. 191 



4, 5.) Here then is the adversity of the case. The cater- 

 pillar cannot meet her companion in the air. The winged 

 rover disdains the ground. They might never therefore 

 be brought together, did not this radiant torch direct the 

 volatile mate to his sedentary female. 



In this example we also see the resources of art antici- 

 pated. One grand operation of chemistry is the making 

 of phosphorus ; and it was thought an ingenious device, 

 to make phosphoric matches supply the place of lighted 

 tapers. Now this very thing is done in the body of the 

 glow-worm. The phosphorus is not only made, but kin- 

 dled ; and caused to emit a steady and genial beam, for 

 the purpose which is here stated, and which I believe to 

 be the true one. 



VI. Nor is the last the only instance that entomology 

 affords, in which our discoveries, or rather our projects, 

 turn out to be imitations of nature. Some years ago, a 

 plan was suggested, of producing propulsion by reaction in 

 this way. By the force of a steam engine^ a stream of 

 water was to be shot out of the stern of a boat ,- the im- 

 pulse of which stream upon the water in the river, was to 

 push the boat itself forward ; it is, in truth, the principle 

 by which sky-rockets ascend in the air. Of the use or 

 the practicability of the plan t 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 

 motion of some species of aquatic insects. The larva of 

 the dragon-jly, according to Adams, swims by ejecting 

 water from its tail ; is driven forwards by the reaction of 

 water in the pool upon the current issuing in a direction 

 backward from its body. (PI. XXXIII. fig. 6.) 



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 appli- 

 cation 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 fre- 

 quently see this spider'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 



