THE LIBRARY. fc 



Considered mineralogically, according to Broigniart ; the 

 classification of rocks considered mineralogically according 

 to D'Omalius : D'Halloy ; the mineralogical classification of 

 rocks according to Coquand ; the classification of Coquand 

 modified by Viianova ; and the dichotomous classification of 

 rocks. The different species are then described according 

 to classes, and orders, and families. 



5. Under the head Petrogenia are discussed succes- 

 sively eruptive rocks and neptunic rocks, in a normal con- 

 dition, divided into those formed by chemical sediment, and 

 those by mechanical sediment ; metamorphic rocks, 

 and rocks of organic origin, divided into those formed of 

 animal remains, and coal formations of vegetable origin. 



6. Under the head of Aleofologia, or the decomposition 

 of rocks, are discussed the various rocks thus produced. 

 And this is followed by a discussion of the general constitu- 

 tion of earths ; of the component parts of these ; of the 

 influence of these upon the properties of the earths thus 

 formed ; the physical properties of earths ; and the classi- 

 fication of earths according to the method of Hundeshagen 

 of Masure, and of Columelo. 



Of this sixth section of the work the Junta Consultiva 

 speak in terms of the highest commendation. 



It appears from their statements, and the statements 

 of others, that facts which are met with scattered and 

 dispersed in various treatises on sylviculture, mineralogy, 

 geology, and other allied subjects, are here presented in such 

 collocation and combination that with ease and advantage 

 there may be deduced from the composition of the soil the 

 vegetation with which it should be covered, and vice versa ; 

 and be determined with certitude the case frequently 

 submitted to the forest engineer to what should be 

 destined certain lands requiring to be replenished ; or what 

 species of trees should make way for others for which the 

 land is better adapted : and this department of study is 

 presented in the work in a simple and attractive aspect, 

 deducing so naturally from the composition of the soil, 

 and the course of the alterations in the nutritive principles 



F 



