142 Germany. 



insect pests increased, hence the interest in the life 

 histories of the pests grew and gave rise to the cele- 

 brated work by Ratzeburg, "Die Waldbverderber und 

 Ihre Feinde" (1841). A number of similar hand-books 

 on insects and on other zoological subjects followed; 

 the latest, a most complete work on insects, being 

 still based on Ratzeburg's work, is that of Judeich and 

 Nitzsche, in two volumes (1895). Of course, the 

 general works on forest protection always included 

 chapters on forest entomology. The first of these 

 text-books on forest protection was published by 

 Lanrop (1811), and others by Bechstein, Pfeil, Kaus- 

 chinger and recently by Hess (1896), and Filrst (1889). 



Knowledge of the soil was but poorly developed in 

 the encyclopaedic works of the earlier part of the period. 



Not till Liebig's epochmaking investigations was a 

 scientific basis secured for the subject. Then be- 

 came possible the improvements in the contents of 

 such works as Grebe (1886), Senft (1888), and of Gus- 

 tav Heyer, whose volume {Lehrbuch der Forstlichen 

 Bodenkunde und Klimatologie, 1856), well records 

 the state of knowledge at that time. But only since 

 then has this field been worked with more scientific 

 thoroughness by Ebermayer, Schrceder, Weber, Wollny, 

 and by Ramann, whose volume on Bodenkunde 

 (1893) may be still considered the standard of the 

 present day (newest edition, 1910). 



The question of the climatic significance of forests 

 is one which first became recognized as capable of 

 solution by scientific means when the movement for 

 forest experiment stations began to take shape and 



