328 
POPULAK SCIENCE REVIEW. 
mainly upon the following conditions: — (1). The temperature of the 
discharging body, and its distance from the electrified one. (2.) The nature 
(+ or — ) of the latter’s electricity. With regard to (1), it is shown that 
the discharging power of a hot body diminishes with its distance and 
increases with its temperature. But, concerning the temperature, it is 
proved that the discharging power of a hot body does not depend upon the 
quantity of heat radiated from it to the electrified body, but chiefly upon 
its quality. Thus a white-hot platinum wire connected with the earth 
may exercise an indefinitely greater discharging power, at the same 
distance, than a large mass of iron at 100° C., though the latter may impart 
more heat to the electrified body. The rest of the paper is of too great 
length to admit of a brief abstract. 
A neat mode of employ mg Bunsen's Flame for Testing Pui'poses has been 
suggested by Mr. C. Huson in a letter to the “ Chemical News ” (May 23rd). 
In principle, this method is similar to that of the Bunsen-stick recom- 
mended in some of the recent text-books, but, he thinks, will be found to be 
an improvement on it, both in neatness and delicacy, and also in expedi- 
tiousness. A thin piece of platinum wire is taken, and a small double loop 
or cage two or three mm. in diameter made at one end. This loop is 
moistened with water and then dipped into powdered cream of tartar, a 
small portion of which will adhere. On heating for a few seconds in the 
reducing zone of the Bunsen flame, the cream of tartar will, of course, be 
converted into a mixture of carbon and potassium carbonate. All that now 
remains to be done is to dip this porous mass of carbon into a solution of 
the substance to be tested, or (in the case of a solid body) to moisten it with 
water and attach a grain or two of the assay to it, and, having flrst driven 
off the moisture by holding the wire at some distance above the flame, to 
insert the carbon tip into the upper reducing flame for a few moments. If 
the solution of the assay be concentrated, or if a solid portion be used, the 
reduced metal will be plainly visible to the naked eye ; but, in the case of 
a dilute solution being used, the metallic grains can only be seen by rubbing 
the carbon tip in a small agate mortar with a few drops of water. 
An Improved Optical Saccharimeter has been devised by M. Prazmowski, 
and is described by him in the ‘‘ Comptes Rendus " (May 12th). His paper 
has been abstracted by the Chemical News,” which says that Soleil's 
instrument requires considerable perfection in the visual organ to appreciate 
exactly the uniformity of colouring in the two halos of the field j and, in 
view of this, some have sought to improve on it by making the observation 
depend on perceiving a slight difierence between two luminous intensities. 
M. Frellet and M. Cornu have suggested means of effecting this. M. Praz- 
mowski’s method is to use a bi-plate of spar (in place of Soleil’s plate with 
two rotations), the face of separation being placed in the principal section 
of the prism. He utilises SoleiTs compensator. 
The French Academy's Bepoi't on M. Boussinesq’s Essay on the Theory of 
Water Currents is to be found in the Comptes Rendus ” of April 14th. 
The committee gave a somewhat lengthy analysis of this important work ; 
in which M. Boussinesq treats of the motion of water in pipes and in open 
channels— considering fluid sections of various forms, especially those which 
are rectangular and of considerable breadth, constant, or gradually variable. 
