514 On the Electrical Terms Intensity and Tension. 



geometrical diagram above referred to, that it could not be other- 

 wise, and is a necessary result of the forces in operation. We may 

 infer from the equality of the triangles A D C, A D B, that at 

 the instant of explosive discharge the force ABD through the 

 external circuit has superseded the force A D C in the direction 

 of the coatings. If, therefore, we suppose discharge to occur 

 with the successive accumulated quantities Ce, C/, C g } &c, 

 then discharge with first quantity — C e at distance A e, force 

 through external circuit will be represented by triangle A m e, 

 and force in the direction of coatings by triangle A m C. When 

 discharge occurs at distance Af=2Ae with a double accumula- 

 tion C/=2C e, force through the circuit will be represented by 

 triangle Anf, and force in the direction of the coatings by tri- 

 angle A n C, and so on. We have here to observe, however, that, 

 in estimating the forces through the circuit, the force for quan- 

 tity C e, and distance of discharging balls A/=2A e, will be no 

 longer represented by triangle A me (when quantity becomes 

 Cf=2C e) y but by triangle A *• e, or one-fourth of triangle A nf\ 

 = force through the circuit at the instant of discharge with a 

 double quantity. When, therefore, distance Ae is increased 

 to Af with the unit of charge represented by C e, then force 

 acting through the external circuit is represented by triangle 

 Are, and not by triangle A me. 



In order therefore to measure a double accumulation by means 

 of a moveable electrometer, we must oppose to the force through 

 the circuit four times the resistance : thus, in the operation of 

 Cuthbertson's ingenious steel-yard discharging electrometer, we 

 must, in order to obtain a double accumulation, set the slider of 

 the balance-arm to four times the number of grains ; in order to 

 obtain a treble accumulation, we must set the slider of the balance- 

 arm to nine times the number of grains, and so on. When, in 

 the application of Lane's discharger, therefore, discharge occurs 

 at a double distance, the quantity of electricity accumulated is 

 twice as great, and the respective forces through the circuit as 

 1 : 4, as represented by the triangles A e r, Afn ; when discharge 

 occurs at a treble distance, the quantity of electricity accumulated 

 is three times as great, and the force through the circuit nine 

 times as great, as represented by the triangles A e s, Ago, and so 

 on, — the force through the circuit being, as already observed, as 

 the square of the quantity. 



15. It may perhaps be as well to further remark that, although, 

 according to the diagram, the forces ABD, ADC are at the 

 instant of discharge considered as equal, we cannot however infer 

 their precise equality, or suppose the decreasing force A D C in 

 the direction of the circuit to absolutely vanish at the point D : 

 hence some little residuum, commonly called residual discharge, 



