94 Geographical Distribution of Insects. 



SECOND CLASS._ACID MOULD. 



Character. — The water in which this mould is digested or boiled red- 

 dens litmus jjaper. 



In each of these classes, the genera are formed by the con- 

 sideration of the tenacity of the soil, which is so very important 

 an element in its characters. 



The work concludes by laying down rules for the descrip- 

 tion of species, and with examples of all the methods of descrip- 

 tion. In reading these, we at once perceive how precise an 

 idea of soils is conveyed in a manner that cannot be misvm- 

 derstood by any agricultm'ist. The possibility of transmit- 

 ting these clear and pointed descriptions to a distance, follows 

 as a matter of course ; and we shall in this manner be freed 

 from all that vagueness which has been so long a just cause of 

 complaint. 



" If I have succeeded (concludes the author) in what I have 

 proposed in writing this book, the study of agricultural trea- 

 tises will be greatly facilitated ; the different methods which 

 are followed in distant countries will no longer appear so 

 marvellous, and will become more intelligible ; we shall com- 

 prehend better the considerations which limit or extend the 

 several cultures, and a necessary link being established be- 

 tween the science of agriculture and other natural sciences, it 

 will become more intelligible to all, and will more readily pro- 

 fit by the progress of all the other branches of human know- 

 ledge." 



On the Geographical Distribution of Insects. 



The geography of animals in general, is a department of 

 their history which owes the degree of progress it has made, 

 almost entii'ely to the exertions of modern naturalists. Their 

 predecessors, with very few exceptions, regarded a descrip- 

 tion of the intrinsic properties of natural objects as sufficient 

 to gratify all reasonable cm'iosity ; and the relations which 

 they bore to climate, temperatui'e, and other physical attri- 

 butes, scarcely ever attracted their I'egard. The subject is 

 now, however, viewed in a more philosophical aspect, and a 



