Learned Societies. 515 
material, whenever it is dried for conversion into cartridges, 
or employment in other ways, will contain the alkaline 
matter required for its safe storage and use in the dry con- 
dition in all climates. Although some experiments, bear- 
ing upon the different branches of inquiry included in this 
memoir, are still in progress, with a view to the attainment 
of additional knowledge of the conditions which regulate 
the stability of gun-cotton, it is confidently believed that 
the results arrived at amply demonstrate that the objections 
which have been of late revived, especially in France, 
against the employment of gun-cotton, on the ground of 
its instability, apply only in a comparatively slight degree 
to the material produced by strictly pursuing the system 
of manufacture perfected by von Lenk; that, as far as 
they do exist, they have been definitely traced to certain 
difficulties in the manufacture of pure gun-cotton which 
further experimental research may, and most probably 
will, overcome ; but that, in the meantime, these objections 
are entirely set aside by the adoption of two very simple 
measures, against the employment of which no practical 
difficulties can be raised, and which, there is every reason 
to believe, must secure for this material the perfect con- 
fidence of those who desire to avail themselves of the 
special advantages which it presents as an explosive agent. 
The nature of the decomposition of gun-cotton when ex- 
ploded under different conditions is now under investigation 
by me, and the results arrived at will, I trust, be com- 
municated before long to the Royal Society. 
THE GEOLOGICAL SOCIETY.—At the meeting held on 
Wednesday, the 17th ult., Sir Charles Lyell in the chair, a 
paper was read by Mr. Etheridge, which in substance was 
a vindication of the Devonian system, as propounded some 
thirty years ago by Sir Roderick Murchison and Professor 
Sedgwick, and since then adopted by geologists throughout 
the world. A paper attacking the system was read before 
this Society by Professor Jukes some time since, and Mr. 
Etheridge’s communication was a reply. The accuracy of 
the received classification was maintained on physical and 
palzontological grounds, Mr. Etheridge arguing with great_ 
ability, and adducing in proof of his argument data of very 
great value, collected and arranged with consummate skill 
vand perseverance. 
OBSTETRICAL SOCIETY OF LONDON.—A largely at- 
tended meeting of this Society was held on the 3rd ult. at 
the rooms of the Medico-Chirurgical Society, for the pur- 
NEW SERIES.—VOL, I. ona ' 
