Phillips 071 Mineralogy. 323 



ftective goniometer — a more certain method than that adopted 

 by Haiiy ;" who always, we believe, used the goniometer in- 

 vented by Corangean. 



In regard to the figures to which the measurements are annexed, it may 

 be observed, that these are not in all cases the representatives of single 

 crystals, for in some of them are associated the planes observed on two or 

 three : thus occasionally rendering the form more complicated than any 

 single crystal 1 have seen, but not more so than may probably be founl 

 hereafter. This mode has been adopted as offering to the student the 

 greatest assistance that I could devise, since it combines at one view all 

 the observed planes, without increasing enormously the bulk, and conse- 

 quent expense of the work, as must have been the case if all the varieties 

 of form had been given separately. 



We had some doubts, on first reading the preceding passage, 

 whether this assembling of planes from different crystals into one 

 sum total may not rather tend to perplex, than instruct the student. 

 On further reflection, however, we are inclined to think our author 

 is right, since a reference to the simpler forms, including the 

 primary, of which a series of smaller figures generally accom- 

 panies the larger, will sufficiently elucidate the more complex, 

 and, in some degree, imaginary, yet still possible, structui'e ; and, 

 in some instances, the planes on an actual crystal are so numerous, 

 that nearly all that are represented on the large figures are dis- 

 cernible. Thus our author mentions a crystal of fluor, from 

 Devonshire, in his own possession, which exhibits all the planes, 

 except four, represented in the elaborate, and beautifully-distinct 

 figure given at page 17O, and would, if perfect, be bounded by 

 322 planes. If the figure we have just referred to was drawn by 

 no " other rule than such as the hand and eye could furnish," as 

 our author tells us the figures generally were, his hand and eye 

 possess a skill and accuracy very seldom indeed to be met with. 



In the useful introduction which precedes the mineralogical 

 descriptions, not much alteration has been made in the present 

 edition ; the division which relates to analysis has been somewhat 

 shortened, and, as well as the summary account of the elements of 

 minerals, improved by a few judicious changes in point of arrange- 

 ment, and in such other particulars as the progress of chemical 

 science during the last four years has rendered necessary. The 

 hypothetical wodanium is, of course, struck out altogether, and 

 amongst the other essential alterations we are glad to see selenium 

 removed from the list of metals, and restored to its more proper 

 association with sulphur, phosphorus, and boron. Mr. Phillips 

 remarks, both in this and the second edition, that we have no de- 

 scription of the iron pyrites from Fahlun, in which this substance 

 is found. If it have any decided external characters, by which it 

 may be distinguished, it is very desirable that they should be pub- 

 lished, for we strongly suspect that many a specimen of common 

 pyrites is sold as seleniferous, which does not contain an atom of 

 selenium. We have ourselves witnessed, more than once, a lively 

 competition for the purchase of such a specimen, said to be from 



