80 Werner's Advice to Students of Geology. 



in geognostical undertakings without a sufficient knowledge of 

 mineralogy ! The book of nature, they said, was open to them; 

 but it was necessary to know the characters in which that book 

 is written, and these characters are, in this case, the simple mi- 

 nerals. 



It is sufficient to bear in mind that natural philosophy makes 

 known the laws which seem to regulate matter ; and especially, 

 that, having the phenomena of nature, and the causes which 

 produce them, continually before our eyes, it enables us to 

 seize and appreciate the relations which may exist between ef- 

 fects which we see, and the causes to which we are led to attri- 

 bute them, to show how necessary this science is to geology, 

 which occupies itself with the revolutions of the terrestrial 

 globe, and which endeavours to account for the changes which 

 its surface undergoes, or may have undergone. 



When this same observer enters into the details of the forma^ 

 tion of minerals, he sees nothing but precipitations, crystalliza- 

 tions, and solutions : the forces which have produced minerals, 

 which have collected and united their elements, are forces of 

 affinity ; he cannot duly appreciate their effects, without a pro- 

 found knowledge of general chemistry. But it is necessary for 

 him to employ much reserve and much discernment when, from 

 Avhat takes place in our laboratories, he would draw inferences 

 respecting what takes place in those of nature. Nature acts on 

 immense masses ; she has time at her disposal, it is nothing to 

 her ; and these two circumstances often suffice to render entire- 

 ly dissimilar the effects of the same agent and the products of 

 the same cause. Besides we cannot flatter ourselves with pos- 

 sessing a knowledge of all the means which nature employs in 

 her formations, — nor can we conclude that she cannot produce 

 a particular effect, because we have not yet been able to imitate 

 it in our laboi'atories ; for example, that a substance is inde- 

 composable, because we have not yet been able to decompose it. 

 The other branches of natural history, zoology and botany, 

 are also of great utility to the geologist. They make known to 

 him that multiplicity of corals, and shells, those remains of other 

 animals, and also of vegetables, which he finds so abundantly in 

 many of the strata of the globe, and which throw so much light 

 upon the different epochs, and upon many other circumstances. 



