189 



generation are precisely similar. Sir Everard points out some errors 

 into which anatomists had fallen in describing these, more especially 

 with respect to the eel tribe, in which the kidneys being immediately 

 behind the peritoneum, and closely connected, the whole mass has 

 been mistaken for kidney. 



In that species of barnacle called Lepas anatifera, the ovaria are 

 situated round the ossophagus, and the ova are impregnated before 

 they leave the ovaria. 



The author concludes this paper with an account of the structure 

 of the organs of generation in the earth worm, and of their mode of 

 copulation. These, as well as the other anatomical facts detailed in 

 this communication, are illustrated by reference to a variety of draw- 

 ings. 



On a New Phenomenon of Electro-magnetism. By Sir Humphry Davy, 

 Bart. Pres. R.S. Read March 6, 1823. [Phil. Trans. 1823, 

 p. 153.] 



About fifteen months ago it occurred to Sir Humphry Davy to try 

 the action of a magnet upon mercury, connected in the electric cir- 

 cuit ; and having very lately had occasion to repeat the experiment 

 in a more perfect manner, by the aid of a battery, consisting of a 

 single pair of plates of about 100 square feet, constructed for the 

 London Institution, under the direction of Mr. Pepys, he is induced 

 to lay the result of the experiment before the Royal Society, as pre- 

 senting a phenomenon which may prove important hereafter in its 

 relations to the theory of electro-magnetism. 



When two wires were placed in a basin of mercury, perpendicu- 

 lar to the surface, and in the voltaic circuit of the above-mentioned 

 battery, the mercury revolved according to the common law of elec- 

 tro-magnetic rotation, upon presenting a magnet either above or 

 below the wires ; and the velocity was increased by using the oppo- 

 site poles of two magnets, one above and the other below the mer- 

 cury. When the pole of the magnet was held above the mercury, 

 and between the two wires, the circular motion ceased, and currents 

 took place in the mercury in opposite directions. These and other 

 circumstances induced Sir Humphry Davy to believe that the pas- 

 sage of the electricity through the mercury, produced motions inde- 

 pendent of the magnet, and that the rotations described were owing 

 to a composition of forces ; and, moreover, that such motions would, 

 from the position of the wires, occur chiefly at the lower surface of 

 the mercury ; he therefore inverted the form of the experiment, 

 bringing the copper wires through two holes in the bottom of a glass 

 basin, with so much mercury in it as to stand one tenth of an inch 

 above the polished ends of the wires. Upon making the communi- 

 cation with the battery, the surface of the mercury was elevated into 

 a small cone above each of the wires, from which waves flowed off in 

 all directions, the only apparent point of rest being central, between 

 the wires. These cones were diminished by the approximation of 



