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POPULAR SCIENCE REVIEW. 
The Diagnosis of the Alga. — Upon this subject a controversy has been 
going on for some time past between Mr. Archer, of the Dublin Natural 
History Society, and Dr. Braxton Hicks, F.R.S. The latter contends that 
there are so many intermediate forms between the earlier and later stages of 
the development of certain plants, which are in every respect like what Mr. 
Archer considers adult forms, that diagnosis from the examination of speci- 
mens alone not undergoing development is unsatisfactory. Dr. Hicks asks 
how Mr. Archer can say whether a specimen is a fixed form, a separate 
entity, or merely a transitorial form of some other growth. To this Mr. 
Archer replies that the mere fact of conjugation taking place is sufficient to 
prove the adult nature of the species under examination. Dr. Hicks, we 
believe, doe3 not look on conjugation a3 a true generative act. — Vide 
Quarterly Journal of the Microscopical Science , October. 
CHEMISTRY. 
Action of Magnesium on Neutral Metallic Salts. — In a paper read before 
the French Academy, on October 1, M. A. Commaille states that hydrogen 
is always evolved when a metal is precipitated by magnesium, and in such 
cases the precipitation is incomplete. In the case of sulphate of iron, 
hydrated protoxide of iron is thrown down ; in an acid solution, metallic 
iron is precipitated. With mixed chromic and chromous chloride, hydrated 
sesquioxide of chromium is precipitated. With manganous sulphate, the 
reaction is the same as with iron. With cobalt sulphate, the reaction is 
very slow ; after a few days the hydrated oxide, Co 3 0 4 , deposits on the 
magnesium. With nickel sulphate, the precipitate formed is the hydrated 
protoxide. With oxalate of uranium, a golden-coloured deposit of hydrated 
sesquioxide is produced — U 2 0 3 ,H0. With sulphate of zinc, there is an 
energetic action, and the metal, the hydrated oxide, and sub-sulphate are 
precipitated. With chloride of cadmium, the reaction is also very energetic, 
and a mixture of oxychloride of cadmium, and metallic cadmium, is preci- 
pitated. Bismuth salts being acid give a precipitate of pure metallic 
bismuth. Protochloride of tin gives spongy tin and stannic acid. The 
disengagement of gas is very strong with neutral chloride of lead; the 
deposit consists of lead mixed with oxychloride. 
Magnesium Rods for Toxicological Purposes. — The Chemical News states 
that some of Mr. Mellor’s magnesium rods which have been examined by 
the editor have been found to answer their purpose exceedingly well. 
They are intended to replace zinc in the detection of arsenic and other 
poisonous metals. When examined in connection with Marsh’s apparatus, 
they gave no indication of deposit which could be confounded by the 
chemist with arsenic, &c. 
Preparation of Pare Caustic Alkalies. — A method by which the carbonates 
may be rendered so pure that they only exhibit traces of chloride has been 
discovered by M. Graeger. This chemist first treats them with carbonate 
of silver, and then boils them with lime from calcined marble. The 
ley is then filtered through a funnel, in the bottom of which are placed 
