HINTS TO COLLECTOES. 93 



to leave the herbage and get on rocks, it is a certain 

 prognostication of wet weather. He adds, that the 

 colour of certain kinds of snail varies according to 

 the quantity of moisture retained. 



As regards the particular time of day to collect 

 with advantage, a search in an open country should 

 be prosecuted after a shower of rain, or during 

 early morn. In damp woods, where throughout the 

 day the air is sufficiently moist to maintain the 

 animals in full activity, no such considerations de- 

 termine the best time for collecting. In such places, 

 light is usually the desideratum, and, consequently, 

 a search at mid-day in a clear sky is most likely to 

 prove remunerative. 



Land shells are most abundant on limestone soils, 

 which are most congenial to their existence and 

 perpetuation ; and in explanation it may be observed 

 that the shell is composed almost entirely of car- 

 bonate of lime ; that the plants upon which the ani- 

 mals feed are the sources whence the mineral matters 

 are derived, and that plants affecting calcareous 

 soils contain proportionately a larger amount of 

 salts than those inhabiting clayey or sandy soils. 

 These, therefore, are in greater request. So also 



