EXORDIUM. 235 



the last impression must be so confounded with the 

 preceding ones that no distinct image can be left. 



But it will probably be asked, why I did not kill my 

 object before J drew it, instead of giving myself all this 

 unnecessary trouble ? I answer, that I never could make 

 a drawing to my mind from a dead aquatic larva or 

 insect. Such is the extreme delicacy of their organs, 

 and so rapid their decomposition in water, that long 

 before a drawing can be executed, the main and capital 

 parts of the internal, and even external structure, in 

 most subjects, will become confused and unintelligible. 

 If they are removed out of the water, a still greater 

 change is effected by their drying : their colours vanish, 

 and their whole appearance is totally changed ; to say 

 nothing of the fact, that a dead aquatic insect so loses 

 the peculiar distinctive character derived from its 

 favourite attitude and position, that though the com- 

 ponent parts might, in some instances, be correctly given, 

 the tout ensemble would be scarcely recognized. Some 

 of the proportions length of the body and legs,&c. may, 

 however, be measured from the dead subject ; and this 

 help I have always had recourse to when I could spare a 

 specimen for destruction. All attempts to preserve these 

 creatures in spirits, turpentine, &c. are useless, from the 

 excessive corrugation these liquids produce. I also made 

 various attempts to confine them in a narrow compass, 

 so as to prevent much latitude of motion ; but was com- 

 pelled to desist from the project, finding that they got 



