the Electro-magnetic Poisier by Sckweigger's Multiplier. 447 



Adding these equations together, there results 



l-62181a:'4-0-0615606 = 0-925556a^^4-0-1207389, 



Also 0'696264.r« = 0-0591783 



x= = 0-084905 



5. Setting out from these principles, I made several series of 

 experiments, in order to develop the law of the relation of the 

 magnetic power of the connectmg wire in Prof Schweigger's 

 multiplier to the number of convolutions it was made to 

 take. For this purpose I made use of a magnetic needle six 

 inches in length, made by M. Kraft an instrument-maker of this 

 town. Glass tubes had been applied to the compass, at two 

 opposite points, through which the wire was introduced. 

 The limb was divided into half degrees, and I could very well 

 estimate small fractions of a degree, by means of a lens. The 

 compass stood upon a vertical pillar, revolving on its axis, 

 at the foot of which was placed a graduated disk three inches 

 in diameter. In this manner I could put the connecting wire 

 into each azimuth, and vary the angle rf as I pleased. I could 

 also use the same needle as a dipping needle; I confined 

 myself, however, to experiments with the variation needle. 



The electromotor I employed was a sunple alternation on 

 Prof. Schweigger's construction (Gehlen's Journal, bd. vii. 

 taf 5. fig. 18: Schweigger and Meinecke's Journal, N. R. 

 bd. i. p. 7); the strip of zinc being about eight inches long and 

 four wide, and that of copper consequently double that size. 

 The fluid conductor was a solution of muriate of ammonia in 

 spring water, to which was added about O'Ol of concentiated 

 sulphuric acid. For connecting wire I made use of copper 

 harpsichord wire, covered with silk du-ead, and connected with 

 the electromotor by finer wire (No. 14). 



To the above I have to add the following observation: 

 Several authors complain, that the results obtained by the 

 electro-magnetic experiments can never be relied upon, be- 

 cause this po-wer rapidly decreases in a short time. The re- 

 mark may be true, but I maintain that this source of error 

 may be entirely avoided. It appears to depend, principally, 

 upon the construction of the electrical apparatus. If a vol- 

 taic ]nle be made use of, the dimirnition of power takes place 

 pretty (juickly ; it is much slower with the ajiparatus consist- 

 ing of a copper vessel in which a plate of zinc is placed ; and 

 it decreases slower still wiUi the couronne dcs tasses. If tlie 

 apparatus just described be em))loyed, however, the diininu- 

 tion of jiower takes place very slowly ; but die precaution is 

 to be taken of first bringing the metals into contact with the 

 conducting wire, and then immersing the electromotor in the 



fluid. 



