Notices respecting New Books. 69 



the mineralogist, as it conf-aJr^o *-u^ „Vp.v,;„„i ^„„„f;nns relating to the 

 alteration of minerals, and describes m detail the characters, o^v^. 

 rence, formation, and decomposition of many of the more important 

 riAnerals which either enter into the composition of rocks or are 

 esstritially connected with them, as the silicates, quartz and other 

 siliceoas minerals, zeolites, felspar, tourmaline, garnet, augite and 

 analogous compounds, mica, chlorite, serpentine, steatite, talc, and 

 magnetic iron-ore. Under the last subject the magnetic influence of 

 rocks is treated, but no allusion is made to the important paper 

 by M. Delesse, published in the Annates des Mines for 1848. 



Wernerian tendencies are strongly exhibited throughout the work, 

 for Prof. Bischof considers that the origin of many minerals may be 

 explained by the aqueous agency, although he does not doubt that 

 their formation may have also taken place by fusion. How far 

 geologists will be inclined to agree with him, that, " with the ex- 

 ception of lava, scorise, and other volcanic products, there is no rock 

 whose igneous origin can be proved with equal certainty," is a ques- 

 tion. That the igneous theory ^er se has been too hastily or gener- 

 ally adopted for the explanation of some of the phsenomena attributed 

 to it, may require further investigation. The combination of both 

 agencies, assisted by thermo-electric action, acting upon masses of 

 rock, may have induced an alteration in their molecular arrangement 

 and brought into play new chemical affinities, thereby eliminating 

 fresh mineral compounds, and which have again been altered by 

 the influence of other processes, perhaps more gradual in their 

 ojieration. 



The study therefore of the conditions under which minerals occur 

 in nature is more important than their mere chemical composition ; 

 for, as remarked by Prof. Bischof, " chemical analyses of minerals 

 acquire a much higher value when their object is not merely the 

 establishment of chemical formulse, but also the elucidation of their 

 genetic origin. Mineralogists have established the important fact, 

 that one mineral may appear in the form of another, and it is the 

 business of chemists to point out by what processes alterations or 

 displacements may be eflfected. It is but rarely that the chemist is 

 able to produce artificially the changes observed in nature ; and in 

 order to trace the various stages of these natural processes, there 

 remains no other course for him to pursue than to ascertain by ana- 

 lysis the increase of the non-essential and the decrease of the essen- 

 tial constituents, and from the nature of the former to draw conclusions 

 as to the processes which were going on in the mineral when found." 



While we feel indebted to the Cavendish Society for the publi- 

 cation of this work, we cannot but congratulate Prof. Bischof in the 

 translation having been entrusted to Mr. Paul *, whose chemical 

 knowledge and acquirements are a sufficient guarantee for the 

 care with which the spirit of the original manuscript is rendered, 

 and who has thus contributed towards the production of a treatise 

 which ought to be acceptable as well as interesting to a large class 

 of scientific readers. 



* The first volume is the joint translation of Dr. Drummoml and B. II. 

 Paul, F.C.S. ; the second volume is entirely translated by Mr. Paul. 



