160 



THE GEOLOGIST. 



into optical properties ; physical properties ; other characters, such as 

 streak, taste, odour, etc ; characters dependent on cohesion; chemical 

 characters; all of vrhich are briefly but intelligibly explained. The system 

 of classification adopted is that used by Mr. Warington Smyth in his 

 lectures at the School of Mines, and the division is primarily into jS" on- 

 metallic and Metallic minerals. The former into the five classes of — 1. 

 Carbon and Boron ; 2. Sulphur and Selenium ; 3. Haloids and Salts ; 

 4. Earths ; 5. Silicates and Aluminates. The latter into four classes — 

 1. Brittle and difficult of Fusibility ; 2. Brittle, easily Fusible and Volatile; 

 3. Malleable, not reducible by heat alone ; 4. Noble Metals, reducible by 

 heat alone. This is followed by a list of symbols and signs, and explana- 

 tions of the technical terms used by jewellers and lapidaries. The book 

 consists of 420 closely-printed pages, and is teeming with outline illustra- 

 tions, small, but carefully executed. As a sample of its plan a single extract 

 will suflEice, and at the same time will probably convey information to 

 some of our readers : — 



"Chloeite, Werner. Hexagonal ; occurs m tabular six-sided prisms. Col our 

 various shades of dull emerald-green in the direction of the axis, and yellowis h o 

 hyacinth-red at right angles to it ; also pure white or yellowish. Massive varieties 

 olive-green. Semi-transparent to sub -translucent. Lustre pearly ; yields to the 

 nail, and when in powder is unctuous to the touch. Streak con'esponding to the 

 colour. H. 1 to 1-5. S. Gr. 2-7 to 2-85. Compact chlorite is amoi-phous. Chlorite- 

 slate posseses a slaty structiu'e, and frequently contains imbedded octahedral 

 crystals of magnetic iron, hornblende, and garnets. Earthy chlorite is composed 

 of small pearly, glimmermg, scaly particles. It has a somewhat greasy feel, and 

 bears a striking resemblance to Green Earth. 



Composition. 4 (Mg Fe), Al, Fe, 2 Si, 3 H = 4 Mg Si-h3H. 



Analysis, from the Pyrenees by Belesse, Silica 32-1, Alumina 

 18-5, Magnesia 36-7, Protoxide of Iron 0-6, Water 12-1 = 100-0. 



Chlorite h'eqtiently contains as much as 8 or 9 per cent, of protoxide of iron ; 

 those kinds which have more (up to 28 or 29 per cent.) are classed with Eipidohte. 

 Eefore the blowpipe some lose their colour and fuse at the edges ; with borax 

 aflbrds an iron-reaction.— ZocaZ^Yies. The tin mines of Cornwall, where it is well 

 known 1iy the name of peach. Also in Cumberland and Westmoreland, and near 

 JJ;nil)( ris in Caernarvonshhe. At Portsoy, in Banffshire, it is mixed with Ser- 

 l)ri!tiii(>, and is frequently cut and polished. — Name. From ;!(Xct)p6s', green. This 

 niiiiriai may be distinguished fi-om mica by its laminae being flexible but not 

 cla.-i ic, u liiU' those of mica are veiy elastic. It has been proposed by Descloiseaux 

 to di\ i(lc clilorite into three groups, Pennine, Clinochlore, and Kipidolite ; to which 

 may be added IjewohiQwhevgiie.— Specimens. British Museum; Case 52. Museum 

 of Practical Geology ; Horse-shoe Case, ]S"os. 1039—1043, 1047." 



In this little book also the various names used by different authors have 

 been introduced, as well as certain terms which, although now obsolete, 

 arc very useful for reading the works of the older mineralogists, in which 

 they constantly occur ; while the copious lists of svnon5^ms are very valu- 

 abU> to the student in perusing the \^■orks of foreign authors. We could 

 say iniu-h more of its merits. It is very easy to " cut up " a bad book, 

 but It IS by no means so easy to say properly all we would of a good one. 

 A\ 0 can recommend Mr. Bristow's book to our student-readers; and, as its 

 pru'o ami dunensions bring it within the reach of every one's means, we 

 advise them to test the value of our praise by buying it and reading it. 



