20 SIXTH REPORT. — 1836. 



desideratum in common electricity, more especially as it may be 

 shown that the divergence of similarly electrified bodies is, in its 

 application to quantitative processes, liable to much discrepancy. 



The author exhibited his new species of balance, some account 

 of which he had already submitted to the Physical Section at 

 the last Meeting of the Association ; since this however it had 

 undergone considerable revision. The reactive force of this in- 

 strument, termed a biple balance from the peculiar principle of its 

 action, is not derived from elasticity as in the balance of torsion of 

 Coulombe, but is altogether dependent on gravity ; it seems ex- 

 tremely well adapted to the measurement of small forces generally, 

 and to researches in electricity and magnetism, and may be con- 

 verted if required into a balance of torsion, free from many difficul- 

 ties of a mechanical kind, generally attendant on the employment of 

 that instrument. 



In examining the operation of the repulsive force between two 



small insulated discs of "4 of an inch in diameter, the author 



finds that the repulsion is not always in the ratio of the quantity of 



electricity with which either, or both the discs is charged ; or as the 



squares of the distances inversely, according to the general expres- 



F 

 sion yT^ deducible from Coulombe's researches. That hence the 



two constants R R of which we may suppose the force F to be 

 made up, do not necessarily enter into the composition of the result, 

 so as to cause the total force to increase or diminish with the elec- 

 tricity contained in either. The author here referred to the tabulated 

 results of above five hundred experiments, taken in a good insulating 

 atmosphere. In these experiments the discs were both equally and 

 unequally charged with electricity in known proportions, and placed 

 at various distances apart. From these results it appeared. 



First, that the forces were only as the squares of the distances 

 inversely when the repelling bodies were equally charged, and to a 

 moderately high intensity, and even then this law did not alwaj's ob- 

 tain at all distances; when the discs began to closely approximate 

 the law was observed to vary, and at last to approach that of the in- 

 verse simple distance. 



Second, the deviations from the general law deducible fi'om Cou- 

 lombe's experiments are more apparent as the intensity of the charge 

 is diminished, the inequality of the respective quantities with which 

 each body is charged greater, and the distance less; under any or all 

 of these conditions, the rate of Increase of the repulsive force dimi- 

 nishes, and the repulsion is at length superseded by attraction. 



Third, the quantity of electricity contained in either of the re- 

 pelling bodies is not always in the ratio of the repulsive forces : thus 

 it was seen by the tabulated results, that the respective quantities of 

 electricity at a constant distance D were in several instances in the 

 ratio of 2 : 1 and 4:1, whilst the corresponding forces of repulsion 

 were as 3 : 1 and 5 : 1 respectively. Hence the electrical reactions 

 may be in one proportion, and the quantities of electricity in another. 



