1822.] New Scientific Books. 157 
powder of cassius is immediately formed, and on this account it is 
recommended as a test of the presence of minute portions of gold. 
Bismuth and zinc also are dissolved by hydrogen gas when treated in 
the above mode. 
VII. Frauenhofer’s Experiments on the illuminating Power of the Pris- 
matic Rays. 
By means of an ingenious photometer, M. Frauenhofer measured, 
with great care, the illuminating power of the different coloured spaces, 
and obtained results very different from those usually given. Oneach 
side of the yellow space, the light varied with very great rapidity, as 
appears from the following measures : é 
Intensity of light. 
At the 22d degree* of the red........... 0°032 
At the 34th degree of the red........... 0°094 
At the 22d degree of the orange......... 0°64 
At the 10th degree of the yellow........ 1°000 
At the 42d degree of the yellow. ....... . 0°48 
At the 2d degree of the blue.......... Liepll ts W 
At the 16th degree of the indigo........ 0-031 
At the 43d degree of the violet......... 0°0056 
The measures here given have no relation to the colours opposite to 
them, as the colours are mentioned merely to point out the position in 
Newton’s spectrum, corresponding to thé’ position in Frauenhofer’s 
spectrum, where the intensity of illumination was measured. The 
colours in Frauenhofer’s spectrum, indeed, do not correspond with those 
of Newton.—(Edin. Phil. Jour.) 
_ ARTICLE XII. 
NEW SCIENTIFIC BOOKS 
PREPARING FOR PUBLICATION, 
A work on the science of mineralogy is just about to make its ap- 
pearance in Germany by Mr. Frederick Mohs, Professor of Minera- 
logy at Freyberg, and will contain the terminology, the rules of the 
construction of Mr. Mohs’ system, and the nomenclature, the charac- 
teristic, and the descriptive part of natural history. The whole to be 
comprised in Two Volumes, 8vo. with plates. An English translation 
will appear at the same time, made under the inspection of the author, 
by Mr. Haidinger, who lateiy visited this country in company with 
Count Brenner. 
Hogg’s Treatise on the Growth and Culture of the Carnation, Pink, 
Auricula, Polyanthus, Ranunculus, Tulip, &c. An improved Edition, 
1 Vol. 12mo. 
* The whole length of the spectrum is here supposed to be divided into 360°; the 
red occupying 45°; the orange 27°, the yellow 48°, the green 60°, the blue 60°, the 
indigo 40°, and the violet 80°, 
