392 
rangement employed was a copper wire-float in a double trough of 
mercury, which cannot easily be explained without a figure. 
This experiment, though quoted by most writers on electricity, is 
understood to be one not easily repeated. Indeed, the author has 
not found an indication of its ever having been repeated with suc- 
cess. The author conceiving that perhaps this repulsion described 
by Ampere might assist in explaining the vibrations of rocking 
bodies through which an electrical current passes (as described in a 
communication by him to this Society in January 1859), devised 
another, and, as he conceives, a more delicate method of testing the 
supposed repulsion of a rectilinear current on itself. This he ac- 
complished by connecting the two poles of a battery by means of 
a piece of copper' wire shaped like a horse-shoe, and laid upon one 
extremity of a slender wooden lever suspended by a fine platinum 
wire, after the manner of a torsion balance. Yet, on the establish- 
ment of the circuit through the bent wire, so far was there from 
being any repulsive force tending to separate the torsion rod from 
the battery poles, that the connecting horse-shoe was sensibly and 
even powerfully attracted to the poles, both while the current 
lasted, and for some time after. 
This experiment seems to throw a doubt upon Ampere’s con- 
clusion. The author believes that his mode of experimenting is not 
only much more delicate than that of Ampere, but also that it 
avoids sources of ambiguity present in the other. 
3. Fragmentary Notes on the Generative Organs of some Car- 
tilaginous Fishes. By John Davy, M.D., F.R.S. Lond. 
and Edin., &c. 
These notes, it is stated by the author, were made at different 
times and places, as opportunity favoured, and are offered as a con- 
tribution to a difficult branch of Ichthyology. 
The generative organs of nine different species are described, with 
more or less minuteness of detail. The species are Squalus squa- 
tina, S. galeus, S, acanthias , S, carcharias, S. centrina, S. Cani- 
cula, Scyllium melanostomum, Haia aquila , and M. oxyrhynchus. 
From the observations made, these species would appear to differ in 
some essential points as regards the reproductive process; some, as the 
S. squatina, being viviparous,— -their ova developed or hatched in the 
