Bronze for Sheathing of Ships:—P hotography. A407 
ora ia in Rain-water.—M. eho Ho has been engaged for 
me time in investigating the proportions of ammonia in rain-water in 
Rs cities and country, taking Paris as one ° lata and for the other the 
old monastery of Liebfrauenberg, situated in the Department of the 
the mean, 3°35 milligrams per liter; while at Liebfrauenberg the rain- 
water contained hardly milligram. srr the excess to emana- 
tions, Boussingault says, that Paris may be viewed as a vast mass 
moking chimneys—a spf little Rininoka to a city which ite 
itself the “ cerveau de Puniver 
Bronze for the Sheathing of Ship s.—M. Bonierre, chemist at Nantes, 
who has studied this subject for some years, has arrived by bis experi- 
ments, at the following conclusion: that by diminishing the propor- 
tion of tin the oxydizable m metal is less uniform in its distribution through 
the plates, and — is a consequent inequality of alteration under the 
influence of seaw His recent researches show that sheathing of 
bronze is peofarable; as regards durability and solidity, to copper or 
rass. he abnormal alterations which have been observed are due to 
defective manufacture. e presence of arsenic does not occasion 
alteration in this alloy as happens for red copper. Bronze that will do 
good service contains in general 4°5 to 5°5 p. c. of tin; that with less, 
alters unequally. The introduction of a little zinc into these alloys of 
copper and tin, improves soe product = favoring the diffusion of the 
positive constituent of the metallic ma 
Photography.—Several cae on photography have been ad- 
dressed to the Academy. One of them relates to the cause of the 
partial reduction which the salts of silver experience in photographic 
. Bertsch ha 
ber for January.— moir of M. Carlet on Eiebncie acid, discovered 
y M. Thenard, and obtained by M. Bouis by means of castor oil_—A 
am on the use of chlorine in analyses by MM. Rivot, Beudant and 
Daguin.—Memoirs of M. Payen and of M. Brame on marl beds and the 
effects of lime in peciciaiasdns oes to by used in the adeiinieteiliots 
of chloroform, by Dr. Baudens.—Notes of M. Favier, M. Bourdaloue, 
M. Breton de Champ, ete., on the iescling of the Isthmus of Suez ; 
according to some, there is a considerable difference of level between 
refe 
method of maparpetations “of sich to himself. 
