Royal Society. 391 



and with an accuracy equal to that of Gauss's formulae, from a very 

 small number of magnetic data determined by observation, and the 

 mean annual temperature of the place. 



Jan. 1.3.— "On the Disruptive Discharge of accumulated Elec- 

 tricity, and the Proximate Cause of Lightning." By Isham Baggs, 

 Esq. Communicated by S. Hunter Christie, Esq., Sec. R.S. 



The author proposes to inquire into the principal causes of the 

 violent and disruptive union of opposite electricities which consti- 

 tutes the electric discharge ; and to apply the knowledge thus gained 

 to the explanation of natural phenomena, and the further proof of 

 the identity of frictional and voltaic electricities. He describes two 

 instruments which he employed for the purpose of regulating the 

 discharges of a Leyden jar, or battery, by adjusting with precision 

 the distances between two brass balls, forming a communication 

 between the inner and outer coatings; allowing of their being 

 charged only to a limited degree of intensity, by carrying off all the 

 electricity beyond that extent ; and thus guarding the glass from 

 the dangers of fracture from an excess of charge. He is led to the 

 conclusion, that with a given dialectric, such as glass, the hmit to 

 the intensity of the charge it can receive varies directly as the cube 

 of its thickness, being in the compound ratio of the resistance it 

 presents to the discharge, which is simply as the thickness, and of 

 the square of the distance of the two charged surfaces, such being 

 the law of electric action. 



When a number of insulated Leyden jars, arranged in a consecu- 

 tive series by connecting the outer coating of each with the inner 

 coating of the next, is charged by means of an electrical machine, 

 the tension of the charge diminishes in each jar as they follow in the 

 series, that of the terminal jar being exceedingly small. On the other 

 hand, when each jar has been charged separately in the same manner 

 and to an equal extent, and then quickly arranged in a series, the 

 jars not touching one another, but the knobs connected with the 

 inner coating of each jar, after the first, being placed at a certain 

 distance from the outer coating of the preceding jar, which in such 

 an arrangement is charged with an electricity of an opposite kind to 

 that of the knob adjacent to it, the author found that the tension of 

 the electricities was greatly augmented, giving rise to violent ex- 

 plosions whenever a discharge occurred. He considers a battery 

 thus constituted as bearing the same relation to a single Leyden jar 

 as the voltaic pile does to a single galvanic circle ; and as affordmg 

 in like manner the means of exalting, to any assignable degree, the 

 electric tension. Adopting the views of Mr. Crosse as to the con- 

 stitution of a thunder-cloud, namely, that it is formed of a number 

 of concentric zones of electricity, alternately positive and negative, 

 the central one having the highest intensity, and the tension dimi- 

 nishing in the successive zones surrounding the innermost, till it 

 became inappreciable in the one most remote ; the author considers 

 this condition of the cloud to be analogous to that of the battery 

 above described, and the i)henomena of the former to receive com- 

 plete illustration from the experimental results obtained with the 

 latter. 



