170 Mr. Herschd on certain Motions produced in Fluid [Sept. 



Article II. 



The Bakerian Lecture. — 0>i certain Motions produced in Fluid 

 Conductors when transmitting the Electric Current. By 

 J. F. W. Herschel, Esq. FRS * 



1. Having had occasion, in the course of some enquiries 

 respecting the decomposing agency of the Voltaic pile, to elec- 

 trify mercury in contact with various saline solutions, I was sur- 

 prised to observe motions take place in the fluid metal of a 

 violent and apparently capricious kind, for which, as I had 

 uniformly operated with very feeble electric powers, there seemed 

 no adequate cause. Frequently it would be agitated with con- 

 vulsive starts ; sometimes currents and eddies of great violence 

 would be formed in it ; at others, it would spread and elongate 

 itself, ramifying out into the most irregular forms ; and alto- 

 gether presenting appearances of a nature so singular, as in- 

 duced me to make experiments with a view to ascertain their 

 cause, or at least the circumstances essential to their reproduc- 

 tion. 



2. The singular convulsive agitations into which mercury is 

 thrown when placed within the circuit of a powerful Voltaic 

 battery discharged through water, has been noticed by Sir H. 

 Davy, in his Elements of Chemical Philosophy. Pure water, 

 however, is so very imperfect a conductor, that great Voltaic 

 powers must be used ; and the phaanomena are then too irre- 

 gular, and the agitations too violent for distinctness. It is 

 only when liquids which conduct well are used to form the cir- 

 cuit, that they become regular, and can be studied at leisure 

 under the influence of moderate electric energies. 



3. If a quantity of very pure and perfectly clean mercury, 

 free from the slightest superficial film, be placed in a Wedge- 

 wood-ware evaporating basin (which must also be scrupulously 

 clean), and covered to the depth of about a quarter of an inch 

 with concentrated sulphuric acid, and the extremities of two 

 wires of platina in connexion with the poles of a Voltaic t appa- 

 ratus be immersed in the acid onlu on opposite sides of the 

 mercury, but not in contact with it; immediately a rapid circu- 

 lation will be seen to take place in the acid, owing to a violent 

 current which establishes itself between the two wires, setting 

 directly across the mercury in a direction from the negative (or 

 zinc) towards the positive (or copper) pole. This current is 

 kept up steadily, and without any change in its direction or 



* From the Philosophical Transactions for 1824. Parti. 



•j- The battery I employed in this and the subsequent experiments (unless where the 

 contrary is expressed), consisted of ten pairs of single plates, each of fourteen square 

 inches in surface, excited by mixed nitric and sulphuric acids much diluted. 



