378 Bibliographical Notices. 



would ask any mineralogist how he would like to have no better 

 guide in the determination of a mineral than such a character as the 

 following : — 



IV. ORDER Molibdexides. 



Minerals containing metals of the lead series, in various states of combi- 

 nation ; solid. 



1. Family. — Molibdides. — Minerals containing lead, either native or in 

 combination. — Occurs 1, native, monometric, H. 1'5, sp. gr. 11\381 ; very 

 rarely ; 2, as Sulphuret or " Galena," monometric, H. 25, sp. gr. 7'5, colour 

 and streak lead-gray, easily fused, frangible in beds and veins in crystalline 

 and uncry stalline rocks ; 3, as Oxide or " Minium," pulverulent, in minute 

 rhombic prisms ; sp. gr. 4'6, in veins of galena and calamine ; 4, as Car- 

 bonate or " Cerusite," in right rhombic prisms, H. 3-3 - 5, sp. gr. 6"4, lustre 

 adamantine, colour white or gray, very brittle, in many lead mines ; 5, as 

 Phosphate or " Pyromorphite," in hexagonal prisms, H. 3"5-4, sp. gr. 7 ; 

 colour green, yellow, or brown ; lustre resinous, brittle, in veins with other 

 lead ores ; 6, also less frequently combined with selenium, tellurium, anti- 

 mony, arsenic, vanadic, chromic, molybdic, and tungstic acids. — Metallic 

 lead fuses at 612° F., its soluble salts give a black precipitate with hydro- 

 sulphuric acid. — Symb. Pb. 



This is followed by 2. Family. — Baryides\, but we need go no 

 further. 



In conclusion, there is one point to which we must advert, although 

 in so doing we shall perhaps be running some risk of placing ourselves 

 in the same category with the famous Shandean critic, who carried 

 his rule and compasses in his pocket, and determined the merits of a 

 book by the scmareness of its corners, — we allude to its mechanical 

 execution. We have always entertained an opinion that the great 

 object of a " Manual " should be to furnish its readers with the 

 greatest possible amount of information in the smallest possible 

 amount of space, but the present work appears to have been got up 

 on a directly opposite principle, — it is printed in a positively large 

 type, with spaces between the lines, and the characters of the families 

 are considerably indented, so that in most cases at least a tenth part 

 of the page is actually lost. Had a type of moderate size been em- 

 ployed and the present absurd arrangement of the pages avoided, 

 there is no doubt that at least half as much more information might 

 have been got into the same space. 



We have completed a most thankless task, for few things can be more 

 distasteful to us than to speak unfavourably of the efforts of others, 

 especially when, as in the present case, they appear to have devoted 

 considerable labour to a mistaken attempt to aid in the diffusion of 

 knowledge. But this book unfortunately by no means satisfies the ex- 

 pectations called up by its title, and there can be no doubt that, as far 

 as it is concerned, the author of the next ' Manual of Natural History ' 

 may justly echo the authors' own lamentation, that " no work has 

 yet appeared, comprising either succinctly or in detail, a compre- 

 hensive outline of natural history." 



