22 



REVIEWS. 



arrangement, which he believes to be the one best adapted for the Geological 

 student." With the arrangement of the Mineralogy we find no fault, as we 

 believe it, although not strictly scientific, to be practically useful to the 

 beginner. We could wish, however, that, in the modifications which the 

 mineralogy has undergone, such errors as the following had not been care- 

 fully reproduced in the second edition : — 



" Thus, for example, Calc Spar, in its purest form of Iceland Spar, is found to 



consist of 



Carbonic acid . . . 43*71) , AAnn 

 Lime .... 56-29X 100 ' 00 > 



and if this is reduced to show the atomic relation, we shall find that the real 



proportion is two atoms of carbonic acid to one atom of lime, which represents 



the true nature of the mineral." — p. 157. 



We venture to assert that there is not a lime-burner in the country, who 

 would not become conscious of the fact in a few hours, if Professor Ansted's 

 description were to become true of Calc Spar. 



To show that the foregoing is fairly attributable to ignorance of 

 Dufrenoy's meaning, from whom it is translated, and not to accident, we 

 subjoin the following additional elucidation : — 



" In the case of Iceland spar, already mentioned, the mineral may be regarded 

 as made up of two compound atoms of carbonic acid and one of lime — the com- 

 pound atoms consisting in the one case of two atoms of oxygen and one of carbon, 

 and in the other of one atom of oxygen and one of carbon:' — p. 159. 



A detailed blunder of this description is far more dangerous to the learner's 



progress than a simple mistake, as it produces upon his mind all the effect 



of a circumstantial falsehood, which is well known frequently to deceive 



even the expert. 



Such lamentable ignorance of the elements of Chemistry, would be very 

 unpardonable in a teacher of Geology, were it not, unfortunately, very 

 common ; and we mention this and similar cases which have occurred to 

 us, on a hasty perusal of this book, simply to place the reader on his guard, 

 not to take everything for granted which he may see in print, and not at 

 all with any wish to detract from the real merits of the book, which we 

 believe to be considerable. 



We go on to notice a few more errors in the Mineralogy, with the hope 

 that they may be corrected in a new edition. 



In page 177, Meerschaum is described as an earthy and siliceous car- 

 bonate of magnesia. It is an Hydrated silicate of Magnesia, and contains 

 no carbonic acid. 



In page 217, Vitreous copper ore, or Redruthite, is described as Bisul- 

 phuret of copper. This is not correct, and shows a want of knowledge of 

 Chemical nomenclature. It is a Disulphuret of copper. 



