Mechanical Science. 381 



hours. It was also equally convinced, that ultimately, they would 

 be introduced on board vessels without inconvenience, and thus 

 have the effect of establishing a sort of equilibrium between vessels 

 of different dimensions. Proceedings of the Academy of Sciences,-^' 

 Ann. de Chim. xxvi. 438. 



5. Freservation of Fish during Carriage. — For ensuring the sweet- 

 ness of fish conveyed by land carriage, it is proposed, that the belly 

 of the fish should be opened, and the internal parts sprinkled with 

 powdered charcoal. — N. M. Mag. , 



6. Artificial Puzzolana. — M. Bruyere finds that an excellent 

 artificial puzzolana may be obtained by heating a mixture of three 

 parts clay and one part slacked lime, by measure, for some hours 

 to redness. M. de St. Leger also finds these proportions to be the 

 best, and prepares the substance for sale. — Ann. de Mines, ix. 550^ 



II. Chemical Science. 



1. On the nature of the Electric Current. By M. Ampere.— M. 

 Becquerel having constructed an electrometer of excessive sensi- 

 bility, M. Ampere was desirous of making an experiment with it, 

 illustrative of the nature of the current of electricity produced by 

 contact, and that produced by an electrical machine. 



It is well known that when a plate of zinc and a plate of silver 

 nre soldered together, and one of them insulated, except by the 

 other metal, a constant difterence of electric tension is established 

 between them. The object of the experiment was to verify the 

 supposition that this difference existed even when the two plates 

 were in communication, by being plunged into a liquid conductor ; 

 and M. Becquerel found that the tension did not sensibly diminish 

 even when the liquid was acidulated water, and an intense elec- 

 trical current was produced. This experiment proves that the two 

 electricities developed by contact in the zinc and copper, are pro- 

 duced with a rapidity infinite, as it were, in comparison with the 

 rapidity with which they can traverse acidulated water. It shews 

 also, why no sensible electro-dynamic (electro-magnetic) effect can 

 be produced with a current excited by friction, as for instance, by 

 connecting the conductors of an electrical machine with the wires 

 of the galvanometer. Friction can only excite a certain quantity 

 of electricity in a given time ; but the contact of two different metals 

 supplies it indefinitely as fast as it is carried off' by the fluid con- 

 ductors : for as fast as they diminish the tension by the removal of 

 the electricity, it is renewed at the point where the two metals arc 

 in contact. 



