50 ULTIMATE UTILITY OF THE ABSTRACT PHILOSOPHICAL 



to destroy the larvae; for to rest content with having cut 

 down the trees without destroying the larvae, or even re- 

 moving the trunks from the vicinity of the sound wood, would 

 be, he observed, in reality, to do no good at all. The time 

 hitherto selected for cutting down the dead Elms in the Parks 

 had been just after all the mischief for the season had been 

 effected ; and when all these nurseries of Hylesini had sent 

 forth their inhabitants to the air, for the injury of such trees 

 as might have remained free from infection. With respect to 

 the less infected trees, when the branches were diseased, Mr. 

 Macleay recommended them to be lopt off and burnt ; and 

 for those with the trunks infected, he recommended a coating 

 of tar mixed with train oil, applied to them in March*. 



These recommendations were adopted, or similar means 

 employed, and the remaining trees were happily preserved; and 

 there can be no doubt, that, had the possessors of the forests 

 in the Hartz been, in the first instance, acquainted with the 

 true cause of the disease, those forests might in like manner 

 have been saved. 



From a review of the facts which I have related, we may 

 draw several inferences, having a very direct bearing on the 

 subject immediately before us. We observe, in the first place, 

 that the want of Entomological knowledge, the want of know- 

 ledge of the timber-eating insects, in particular, was the 

 cause of no means having been taken to check their ravages at 

 the outset, either in the forests of the Hartz, or in the Parks of 

 London. Secondly, that when the cause of the disease was so 

 far known, the want of the knowledge of the circumstances 

 attending the Metamorphosis, or change from the grub- to 

 the winged-state, of the devouring insects, caused the trees 

 to be cut down only at the wrong time, the door to be shut 

 when the thieves were gone, and thus rendered this labour 

 perfectly nugatory, or perhaps absolutely mischievous, by re- 

 moving trees, already infected, which might have retained the 

 insects from the sound ones. 



This is merely a specimen, selected from among many 

 others, perhaps equally striking, which might be cited, of the 

 facts evincing the value of the knowledge of Natural History, 

 in the ordinary affairs of life. But a stronger proof, I con- 

 ceive, cannot be adduced. It may be observed, also, that it 

 shows the value, not only of what is called a popular knowledge 

 of the subject, but that of definite and truly scientific informa- 

 tion respecting the objects of nature, that is, of an acquaint- 

 ance with the Natural Sciences themselves, not merely with 



* Edinb. Phil. Journ. vol. xi. p. 123, et set/. 



