SCIENTIFIC SUMMARY. 
113 
simply laid down near the gate and not even nailed to it, this twenty-five 
pounds would shiver the gate into splinters. The bag, which suits the gun- 
powder, happens not to suit the gun-cotton. 
A neiv Method of Estimating the Per-Gentage of Astringent Matters in 
Plants is described by M. Commaille in the Comptes Rendus for August 22. • 
It is proposed by this chemist to employ iodic acid in the determination of 
tannic and gallic acids, and his method of procedure is as follows : He takes 
a known volume of liquid holding in solution the astringent matters^, and 
into it he drops a few minims of dilute prussic acid ; next he takes a known 
volume of a solution of iodic acid of a definite strength. These are mixed 
and boiled for about a quarter of an hour. Then, when the liquid is cool, a 
small quantity of washed animal charcoal is shaken up with it. The astrin- 
gent matters combine with portions of the iodic acid, and then the remaining 
portion is estimated as iodate of sliver. This process shows how much iodic acid 
has combined with the tannin and gallic acid, and as this is constant, the difficulty 
is solved. M. Commaille found that a gramme of gallic acid destroys 2'336 
grammes of iodic acid, and that a gramme of tannin absorbs 2'320 grammes 
of the same compound. 
GEOLOGY AND PALEONTOLOGY. 
Aqueous Agencies versus Plutonic Ones. — In Sir R. Murchison’s anniver- 
sary address to the Royal Geographical Society, we find an allusion to M. 
Schmidt’s opinions upon the above subject. It appears that, according to 
the researches of this geologist, aided by the botanist Glehn and the topo- 
grapher Schebunin, the region beyond the sea of Baikal is distinguished by 
a great number of geological formations. Crystallme rocks, however, abound, 
and the unaltered sedimentary fossiliferous formations are much less extended. 
Among the latter, the Devonian and Jurassic deposits have been best recog- 
nised. The latter have the petrographical characters of the Jurassic rocks of 
the Caucasus, and contain certain beds of coal, which in one spot are said to 
pass into graphite. Farther eastward, and along the Saigon, or chief moun- 
tains, and on the Amur, below the juncture of the Zeia, there are spread out 
great fresh- water formations of tertiary age ; whilst in the great island of 
Sakhalin very recent marine tertiaries repose on true chalk and cretaceous 
deposits. Having discovered what he believes to be many transitions between 
crystalline rocks and unaltered sediments with fossils, M. Schmidt is of 
opinion that all such changes have been brought about in an aqueous manner 
and not by any plutonic or igneous action. Sir Roderick does not apj)ear 
inclined to accept this view, and goes on to say, that the ingenious author 
is obliged, however, to admit the existence of obsidian in one place, and has 
not yet developed his proofs in favour of his novel system, in which, if I have 
not been misinformed, he seems to carry the chemical and neptunic theories 
of Bischoff, to what, I cannot but consider, an extravagant length.” — Vide 
Address at the Anniversary Meeting of the Royal Geographical Society, for 
1864, p. 40. 
Characters of the Beds constituting the Quaternary Formation. — M. Hebert 
has contributed a most instructive memoir, upon the clays and gravels of 
these deposits, to the Bulletins of the Geological Society of France. These 
VOL. IV. NO. XIII. I 
