240 M. Marianini on an analogy^ &c. 



traversing a liquid, or where other currents circulated, and 

 those created by the same current, while another electricity 

 did not pass through the same conductor. 



12. It is demonstrated by the preceding experiments, that 

 the conductibility of liquids for electricity is not changed by 

 the invasion of one, or many currents of electric fluid. We 

 may perhaps find these facts more favourable to the theory of 

 Franklin, than to that which considers electricity as composed 

 of two fluids. (See note at the end.) 



My wishes will be accomplished, if I have shown that when 

 two or several electric currents traverse simultaneously a con- 

 ductor crossing one another in any way, vvhether they are all 

 in the same direction, or some in the opposite direction to 

 others, and whether they are produced by equal or unequal 

 batteries, one of these currents does not experience from the 

 action of the rest any sensible alteration. In this fact we have, 

 if I mistake not, a new and remarkable analogy between 

 the propagation of electricity, and that of light. 



Note by the Author. 



In the examination which I have made of the causes which 

 render galvanic apparatuses, constructed after the method of 

 Novellani and Wollaston, more powerful than others, and 

 which I have published in my essay on electrometric experi- 

 ments, I have discovered a fact which is much better explain- 

 ed by the theory of Franklin than by that of two fluids. 

 It is this. If, in a battery of 2 pair of plates, the electro-ne- 

 gative plate is more immersed in the fluid, the effect is greater 

 than when it is the electro-positive plate which presents the 

 largest wetted surface. 



I may be permitted here to mention another fact which 

 equally supports the theory of a single fluid. 



Take a sheet of pewter, or any other metal, eighteen or 

 twenty centimetres square, terminated on one side by a narrow 

 band or tail ; plunge this sheet in one glass of water, and let 

 the tail be immersed in another. In the glass which holds the 

 band, place another electro-positive plate, of zinc for instance, 

 and in the other glass a similar plate, but electro-negative, for 

 example of copj^er. (Neither of the plates should touch the 



