420 Chronicles of Science. [ July, 
they are covered with a dull dark-coloured crust, whilst internally 
they exhibit a bluish-grey colour, somewhat resembling the well- 
known meteorites of L’Aigle, in France.* 
In spite of the value and variety of our British minerals, we 
have hitherto been without any work treating specially of their geo- 
graphical distribution. Mr. Hall has therefore rendered a service 
to our science by collecting and arranging the principal mineral 
localities in Britain, and publishing them in the shape of a ‘ Direc- 
tory. + The topographical portion of the work is preceded by an 
alphabetical list of our 246 British species and sub-species, showing 
the percentage composition of each. The localities are arranged 
under their respective counties, and when possible the geological 
position of each mineral is noticed. Nothing would be easier, were 
we so disposed, than to poimt out numerous omissions and errors ; 
but we refrain from doing this, under the belief that it would be 
wrong to seek perfection in the first edition of a work of reference 
of this character. 
The continuation of Kenngott’s ‘ Forschungen,’ noticed in the 
Chronicles of last quarter,{ has since been published in the shape of 
a bulky octavo,§ and the compiler turns out to be Dr. Kenngott 
himself. 
Dr. Schrauf, of Vienna, has lately given us the second volume 
of his elaborate work on Physical Mineralogy,|| the earlier volume 
of which has already been noticed in this Journal.{] 
Tridymite is the name which Yom Rath proposes for a new 
Mexican mineral which promises to become of considerable interest ; 
but as only a short preliminary notice has yet been published, we 
defer our description until we are in possession of further details.** 
11. PHYSICS. 
Arter a long series of experiments, Baron von Liebig has finally 
adopted the following process for silvering glass for optical purposes. 
The solutions employed are:—I. One part of fused argentic nitrate 
dissolved in 10 of water; II. (a) Commercial nitric acid, free from 
* «Pogeendorf’s Annalen,’ 1868, No. 2, p. 351; ‘Geol. Mag.” May, p. 248. 
+ ‘The Mineralogist’s Directory; or a Guide to the principal Mineral Locali- 
ties in the United Kingdom of Great Britain and Ireland.’ By Townsend M, Hall, 
F.G.S.. London: 1868. 8vo, pp. 168. 
} P. 256. 
§ ‘ Uebersicht der Resultate Mineralogischer Forschungen in den Jahren. 
1862-65,’ entworfen von Dr. Adolf Kenngott. Leipzig: 1868. 8vo, pp. 482. 
|| ‘Lehrbuch der physikalischen Mineralogie,’ von Dr. Albrecht Schrauf. 
II. Band. ‘Lehrbuch der angewandten Physik der Krystalle. Vienna; 1868. 
8yo, pp. 426. 
{ Quart. Journ. Sc., vol. iii., p. 293. 
** «Pogo, Ann.,’ 1868, No. 3, p. 507; ‘Geol. Mag.,’ June, p. 281, 
