Chemical Science. 1 69 



hauling down the lower ball and leaving the upper one, could be 

 observed with the greatest precision by any officer with a teles- 

 cope. The two balls might be hoisted separately; the first ten 

 minutes before the time, as a preparatory signal ; and the second 

 after an interval of six or seven minutes. 



The best hour would be one p. m. as the crews are then gene- 

 rally at dinner, and as the astronomer would have had time to 

 reduce his observations of the sun's transit, or to calculate the 

 rate of his clock if no observation should have been obtained. 



Yours, &c. 



B. 



Chemical Science. 



1. On the Electrical Effects observed during Chemical Action. By 

 M. Becquerel. — In his last memoir * M. Becquerel had pointed out 

 many sources of electricity, as the contact of the vessels and liquids, 

 which had exerted an influence during his earlier researches into 

 the electrical effects produced by chemical affinity. In the one, 

 of which the following is a brief account, the precautions which 

 were adopted to obviate those disturbing influences are described : 

 most of the former results are confirmed, and new ones added. 



With regard to the electrical phenomena produced when acids 

 and alkalies combine : Two equal porcelain capsules were taken; 

 into one was put an alkaline solution, into the other an acid. The 

 two fluids were connected by a plate of platina, and the platina 

 extremities of the galvanometer wire were inserted one into each 

 capsule. In this state, things being equal on both sides, there 

 was no electrical action, but a wick of amianthus being laid on 

 the intermediate platina so as to connect the acid and the alkali and 

 bring them together, the magnetic needle was immediately affected 

 so as to indicate that the positive electricity left the acid, and the 

 negative electricity the alkaline solution, affording a full confir- 

 mation of the preceding results. 



With respect to what takes place when an acid acts chemically 

 on a metal, independent of the electro-motive force due to mere 

 contact of the acid. A plate of gold is to be fixed in the platina 

 forceps, terminating one end of the galvanometer wire, but pre- 

 served from actual contact by the intervention of some filtering 

 paper. The whole of the gold, with the forceps also, are to be im- 

 mersed in nitric acid contained in a platina capsule; and the other 

 platina extremity of the wire is also to be introduced. In that 

 state there are no electric ettects, but the addition of a single drop 

 of muriatic acid causes action on the gold ; the needle deviates, 

 and, by its direction, shews that the acid, as before, has taken the 

 positive electricity, and the gold the negative. 



• Sec our last Number, p. 37 1. 



