394 Scientific Intelligence. [Nov. 



position. Two copper urires which are soldered each by one of their 

 extremities to a plate of platinum, have these extremities in contact 

 with the mercury, while the other two extremities are united, the 

 one to the galvanometer and the other to a copper plate. The second 

 extremity of the galvanometer is soldered to a zinc plate. The cop- 

 per and zinc plates possess the same dimensions, — the side being a 

 decimetre (3*93 inches) in length. The galvanometer is provided 

 with two needles, and the copper wire which forms the circumvolu- 

 tions consists of live wires, united and soldered at their extremities. 

 The heat of the finger alone, applied to an iron w^ire wound round 

 the extremity of the galvanometer developes a thermo-electric current, 

 producing a deviation of 60». 



While endeavouring to obtain a constant current he found that 



1. The loss of electro-magnetic power is very rapid immediately 

 after the circuit is completed, the eflfect being greater in proportion 

 to the intensity. 



2. This power continues to diminish during a greater or less time 

 after the communication between the two poles has been established. 

 The motion at last ceases, and the power remains the same during a 

 very considerable time. 



3. The time required to arrive at this point is proportional to the 

 original electrical power. 



4. When the same liquid is in contact with all the pairs of a pile 

 the electro-magnetic power reaches its maximum of intensity, with a 

 rapidity proportional to the number of the pairs of plates. 



5. Piles previously charged, but without completing the circle, 

 attain more rapidly the point at which their electro-magnetic power 

 becomes constant. 



6. A pile, when it has arrived at the point where its effect is per- 

 manent, recovers a portion of the electro-magnetic power when the 

 circuit is interrupted which had been completed for some time. In 

 again establishing the communication the power returns to the point 

 at which it left off. This trial may be repeated several times with 

 the same effect. 



7. The electro-magnetic power is rapidly developed at the instant 

 when the circuit is interrupted. 



8. When the electro-magnetic power, proceeding from a pile of 

 four or eight pairs, is revived, the liquid employed being well-water, 

 or water slightly saline, the power is never equal to the original 

 intensity. 



He had recourse to two methods for the purpose of obtaining a 

 constant current. The shortest method was to allow the needle to 

 acquire a fixed deviation, then having interrupted the circuit, to close 

 it at the end of five minutes, for an instant, which is sufficient to 

 obtain a complete deviation ; he observed the number of degrees 

 which the needle indicated. The deviation remained the same, in 

 repeating the operation every five minutes during a long time. The 

 following are the results obtained for the conductibility of different 

 solutions, the quantity of water being 1000 to 10 parts of the dissolved 

 substance : — 



