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POPULAR SCIENCE REVIEW. 
gypsum, placed in a solution of arseniate of ammonia, has been converted 
into arseniate of lime. With a solution of aluminate of potassa and 
gypsum, the result is the formation of glauberite (double sulphate of lime 
and potassa, the latter substituted for the soda in the mineral just named). 
Pieces of galena, kept for twenty years in a solution of bicarbonate of po- 
tassa, have yielded well-defined crystallised carbonate of lead. When pieces 
of limestone were immersed into a solution of plombite of potassa (solution 
of oxide of lead in caustic potassa), the result was the formation of 
beautifully-crystallised hydrated carbonate of lead ; malachite has been 
obtained by the action of limestone upon nitrate of copper, converting it 
into subnitrate, which, in its turn, is converted into malachite by bicar- 
bonate of soda. 
The Teaching of Elementary Chemistry. — At the meeting of the British 
Association (Brighton), Dr. Wood read a paper on this subject. The sum 
and substance of his communication was that, in his experience, it was im- 
possible to teach practical chemistry successfully in towns or places where 
there were no regular laboratories, and he strongly advocated the public 
appointment of such laboratories, where boys could be sent to gain the 
necessary knowledge. His opinion was that the recognised public examina- 
tions in chemistry were too difficult, that the standard was too high for 
young boys. Dr. Wood also proposed that the several great examining 
boards shall agree to use a common standard for elementary examinations, 
and should rigidly adhere to the conspectus. A very full discussion took 
place, in which some valuable suggestions were made by Professors Wil- 
liamson, Lemoine, Barrett, and others engaged in the public teaching of 
chemistry. The president, in summing up the discussion, alluded to the 
great importance of teaching chemistry to every educated individual, and 
furthermore called the attention of the Section to the opening address of 
Dr. B. Sanderson in Section D, who had given a very high opinion of 
the necessity of chemical knowledge to everyone, irrespective of their 
calling. 
A new Vegetable Ink. — In “Les Mondes,” July 4, the editor states, that 
experiments are being made to acclimatise in Europe the Coriaria thymifolia, 
or ink-plant of New Grenada. The juice of this plant, locally termed 
chanchi, is at first of a somewhat reddish colour, but becomes intensely black 
in a few hours. This juice can be used for writing without requiring any 
further preparations ; it corrodes steel pens less than ordinary ink, and has, 
moreover, the advantage of better resisting chemical agents. When the 
portion of America named above was under Spanish dominion, all public 
documents were written with chanchi, which was not removed from paper 
by sea-water. 
On Meteoric Iron. — At the British Association, Prof. Mallett, U.S.A., ex- 
hibited three specimens of iron from Augusta, co. Virginia. One had been 
cut from the original mass by a planing machine, and without further pre- 
paration had been forged into a tolerably perfect blade for a paper-knife ; 
another had been heated to redness in a vacuous porcelain tube (for the 
purpose of examining the occluded gases), and had then been with great 
difficulty Gorged into a blade of similar kind, in which cracks and flaws 
were visible. The third had been heated in like manner in vacuo, but to a 
