Memoir of M. D' Aubiiisson de Voisins. 209 



belonged to the good school of geologists, — the school of ob- 

 servers, — created, so to speak, by Saussure and Werner. As 

 I'eserved as these great masters, he supplied in the least pos- 

 sible degree the silence of facts and the uncertainty of a 

 science as yet but little advanced. A sincere friend of truth, 

 and particularly careful of things positive, he acted on the 

 grand precept of Descartes, which he has inserted in the 

 middle of one of the most beautiful pages of the Introduction 

 to his Treatise : — " He who aspires to a knowledge of the 

 truth must, at least for once in his life, allow himself to doubt 

 of all that he has been taught." A philosophy, we may affirm, 

 by no means adapted to every mind, and which, moreover, 

 does not always lead to the truth ; but which, at least, can 

 alone maintain science and the human mind in the way that 

 conducts to it. 



The impai'tiality of a geologist cannot, however, be carried 

 so far as to make hiin indifferent to all system ; there are 

 certain questions of principles in which M. D'Aubuisson has 

 remained more or less strictly faithful to the Wernerian 

 ideas, and which predominate over all the other classifications 

 of his work. Of this number is the opinion as to the sedi- 

 mentary nature of the granitoidal rocks, — an opinion for which 

 the principal experimental foundation rests, on the one hand, 

 on the uni\ersality of thfse rocks, and their uniformity of 

 composition ; and, on the other, the imperceptible transition 

 so often observed between massive granite and rocks evi- 

 dently stratified, such as gneiss and micaceous slates. This 

 opinion, as is well known, was that of Saussure. It after- 

 wards underwent many modifications, as happens in the natu- 

 ral sciences, where the absolute is unknown ; nor has it yet 

 disappeared ; and it seems to us that it is tending, under 

 new forms, without excluding, as formerly, the action of fire, 

 to revive again in all its force. Let us admit, then, that in 

 this point of view, the work of M. D'Aubuisson, as well as 

 those of M. De Humboldt, remains as a landmark placed 

 on the road which science continually follows. Perhaps there 

 is room to regret that he has not been equally explicit on 

 other subjects ; that he has, for example, given so little space 

 to dynamic geology. Wo find scarcely anything on the causes 



