4S Sig. Dal Negro's Magneto-electi-ic Expetivicnts. 



to the first, and putting both in connection with the galva- 

 nometer, I caused two magnets to enter them contempora- 

 neously, and obtained an effect due to the sum of both pair of 

 spirals. On using still more powerful magnets, even the second 

 galvanometer became useless. The galvanometer which I 

 substituted consists of a rhomboidal needle, about five Paris 

 inches in length, and suspended as in the ordinary compass. 

 The wire which connects the extremities of the spirals passes 

 beneath the needle distant about 3| lines, and is parallel to 

 it when the latter is at rest : on obtaining this fortunate re- 

 sult I conceived the idea of constructing a battery of several 

 magnets put in conflict with an equal number of pairs of 

 spirals. 



Co7istruction of a new Electro-motive Battery. 



6. I had at command only four magnets, so that for the 

 present I am limited in my construction to four pairs of spirals, 

 as in the manner following : On a little table is placed one 

 after the other four pairs of spirals, with the axes horizontal, 

 and so that the perimeters of the cylinders shall have the 

 same horizontal line as a common tangent, it being parallel 

 to one of the sides of the table. On a second table con- 

 tiguous to the first, but not in contact, was placed a little 

 carriage consisting of a rectangular table supported on four 

 wheels, by means of which it could easily receive a motion to 

 and fro. The four magnets were placed upon this carriage, 

 so that the poles of each could move horizontally towards the 

 pairs of spirals, and enter within them. 



The magnets were firmly fixed on the carriage so as not to 

 alter in position, and the latter was so arranged as to move 

 to and fro only in one direction. On moving the carriage, 

 the limbs of the magnets passed at once into all the spirals, 

 and they could be made to enter or move out with the utmost 

 facility, and with any required velocity. 



That the battery thus disposed may give an electric current 

 equal in force to the sum of all the currents excited in the pairs 

 of spirals, it is necessary that all the spirals turning to the 

 right should communicate with each other, that they may form 

 a single metallic wire. The same must be done with all those 

 turning to the left. Then these wires are to be connected in 

 the usual well-known manner with a galvanometer, which 

 we may suppose placed on a third little table, so far distant 

 from the magnets that it may not be influenced by their pre- 

 sence. Although these electric currents are only obtained of 

 instantaneous dui'ation naturally, nevertheless with my battery 

 they may be excited successively with such celerity as to pro- 



