1 42 Royal Society. 



determine its correctness, subjected different metals directly to the 

 same degree of magneto-electric excitation, in such a manner, that 

 the currents excited in them should be in opposite directions (as 

 was the case in Mr. Faraday's experiment), and also that these 

 opposing currents should have the same facility of transmission ; so 

 that the difference of their intensities, if any existed, might admit 

 of measurement. He then minutely describes* the apparatus he con- 

 trived with this view, and which consisted of helices of copper and of 

 iron wire, covered with silk, each making sixty-five turns, but in op- 

 posite directions, and crossing each other alternately, and surround- 

 ing a cylinder of soft iron, which was rendered magnetic by the appli- 

 cation of the large magnet belonging to the Royal Society, which the 

 Council had placed at his disposal while engaged in these researches. 

 The result of the experiment showed that the force of the currents 

 from the copper helix considerably exceeded that from the iron helix, 

 and appeared to be even more than double. By a modification of the 

 apparatus, he found that the intensities of the currents in the two 

 wires were very accurately proportional to their conducting powers ; 

 and hence the uniformity of the results obtained by Mr. Faraday is 

 easily explicable. 



The next object of Mr. Christie was to determine the order of the 

 relative intensities and conducting power of several of the metals : 

 but previously to engaging in this inquiry, he made a series of expe- 

 riments, with a view of determining the law of intensities as depend- 

 ing upon the length and diameter of the wire through which the cur- 

 rent is transmitted. For this purpose it was necessary to devise means 

 of making and breaking the contact in as invariable a manner as pos- 

 sible. This he accomplished by letting the same weight fall from a 

 constant height when the contact was to be broken, and suddenly re- 

 lieving the cylinder of the tension caused by the same weight when 

 the contact was to be formed. He ascertained that portions of wire 

 connected with the one which formed the circuit, but not included in 

 the circuit itself, had scarcely any influence on the intensity of the 

 current. He then enters into various theoretical investigations as to 

 the mode of deducing the absolute intensities of the currents in this 

 mode of experimenting. 



By comparing the intensity of the electricity in wires of one metal 

 with that in wires of each of the others, by means of the arrangement 

 described in the beginning of the paper, and taking a mean of the 

 results, he found the relative intensities in the following metals to be, 

 silver 1520, gold 1 106, copper 1000, zinc 522, tin 253, platinum 240, 

 iron 223, and lead 124. The author compared these results with 

 those obtained by Davy, Becquerel, Professor Cumming, and "Mr. 

 Harris, and states what he considers may have been the causes of the 

 differences. 



The second object of the author's inquiry relates to the law of va- 

 riation of the intensity of the electricity excited in wires of different 

 diameters : for determining which he compares the effects of three 

 different wires of which the diameters were in the proportion of 4, 2, 

 and 1. The results occupy several tables: and the deduction from 



