M. G. Quincke on a new kind of Electric Current. 455 
power is therefore 4, Assuming, therefore, that f'(z)= = we 
find the velocity of the transmission of sound 
1 1 1 
ltotgtete 
1 1 
1 
Labtge iegaie og'-ho ve 
Vie 
als 
This put into numbers, taking “m to be equal to 916 feet, 
gives the velocity of sound equal to 1130 feet. 
Thus we see that the error committed in calculating the velo- 
eity of sound, was not the leaving out the consideration of 
the development of heat, but the supposing the medium of air 
to be continuous. I am surprised to find the result so much 
affected by’a circumstance which appears trifling,—and the more 
so, as the radius of the sphere of sensible molecular action is 
known to be, though finite, very small. The assumption of 
continuity is therefore by no means so allowable as we should be 
inclined @ priori to suppose ; and its effect on the motion of an 
elastic medium is very much greater than was to be expected. 
Sheffield, May 9, 1860. 
[To be continued. | 
LXII. On a new kind of Electric Current. By G. QuiINncKE*, 
NDER the above title, the fifth Number of Poggendorff’s 
‘Annalen for 1859 contains an article of considerable 
length, the leading points in which are contained in the follow- 
ing abstract. 
When pure water flows through a porous body, an electrical cur- 
rent is elicited,—a fact established by the following experiments. 
A plate of burnt clay is luted with sealing-wax between two 
glass tubes of 25 millims. diameter (fig. 1), whose ends are 
worked down smooth. A Wicwah, 
pair of platina wires are ; 
melted into the side of the 
two tubes, and plates of 
platina are riveted on to 
those wires, the wires themselves being connected with the ter- 
minals of a sensitive multiplier furnished with astatic needles. 
The tubes A and B are made smaller at the ends, for the conve- 
nience of connecting them with other tubes. ‘The apparatus 1s 
now filled with distilled water, care being taken that no air 
* Communicated by W. G. Lettsom, Esq. 
; 2H2 
