434 REACTION OF THE INTERIOR OF THE EARTH 



the trachytes of the first division, although, as has been 

 already noticed, leucites also occur in the westernmost 

 parts of the Phlegrsean Fields and on the island of 

 Procida." 



The ingenious author of the classification of volcanoes 

 which has been here introduced, in which they are 

 classed according to the association of simple minerals 

 which they present, by no means considers that he has 

 exhausted the grouping of all that the surface of the 

 earth (still so exceedingly imperfectly explored in a 

 scientifically geological and chemical sense) can offer. 

 Alterations in the nomenclature of the associated mine- 

 rals, as well as an augmentation of our list of trachyte 

 formations, are to be expected in two ways : by the pro- 

 gressive improvement of mineralogy (in more accurate 

 specific distinction, at once according to form and ac- 

 cording to chemical composition), and by the augmenta- 

 tion of our collections, which are in most cases still so 

 incomplete and so little suited for the desired objects. 

 Here, as everywhere, when in cosmical considerations 

 the knowledge of the governing laws has to be attained 

 through a widely comprehensive comparison of particu- 

 lars, we must proceed from the fundamental principle 

 that all that we think we know in the present state of the 

 sciences is but a poor instalment of that which the next 

 century will present. A variety of means are now at 

 hand for accelerating the acquisition of such fuller 

 knowledge ; but there is still great deficiency, as regards 

 the application of thoroughly exhausting methods of 

 examination, in the exploration which has hitherto been 

 made of the trachytic portion of the upheaved, sunken, 

 or fissure-opened surface of the part of the earth which 

 is not covered by the ocean. 



n 



- 







