RECENT PROGRESS IN PHYSICS. 



415 



Fig. 47, 



Ahria could so far investigate their nature as to decide that they are 

 not ellipses, as it would appear at first sight, hut that they are more 

 complicated figures. i • i i t 



Abria ascrihes this effect to the mechanical shock which the dis- 

 charge of the spark occasions in the_ air, and supports this view by 

 producing similar phenomena from slight explosions. 



If small soap hubbies, filled with detonating gas, are exploded upon 

 a marble slab strewed with powder, or if we produce the shock by ex- 

 ploding pellets of fulminating powder on the powdered plate, similar 

 curves Vill be obtained, which, however, in the latter case, will not 

 be so regular as when produced by the explosion of the small bubbles 

 of the detonating mixture. 



§29. Measure of the charge of the battery. — Biess used the follow- 

 ing process for measuring the quantity of electricity accumulated in a 

 jar or battery. (Pog. Ann. XL, 321.) 



The jar or battery 



b (figure 47) to be- 



charged was placed 

 . upon a table insulat- 

 ed by glass legs, and 

 its inner coating con- 

 nected with the con- 

 ductor a of the elec- 

 trical machine, the 

 outer with the inner 

 coating of Lane's 

 measuring jar. The 

 outer coating of the 

 measuring jar was 

 connected with a large metallic surface (a zinc roof) by a wire, so that 

 perfect conduction could be secured. 



The battery having received + E from the conductor of the ma- 

 chine, the repelled -f- E of the outer coating of the battery goes to the 

 interior of the measuring jar, and charges it ; but this charge having 

 attained a certain limit a discharge of the measuring jar ensues, and 

 a new portion of — E can pass from the interior coating of the latter 

 to the exterior of the battery, because the original state of the inner 

 coating of the measuring jar is restored by the discharge, except an 

 inconsiderable residue, which, however, remains the same after all 

 the subsequent discharges. As often as a discharge of the Lane jar 

 follows the continued turning of the machine, the same quantity of — 

 E passes to the outer coating of the battery, and the charge of the 

 battery is increased by the same quantity of electricity ; the charge of 

 the battery, therefore, is proportional to the number of discharges of 

 the measuring jar. 



The distance of the knobs of the measuring jar, in liiess's experi- 

 ment, was first ^ a line, afterwards 1 line ; it remained constant, 

 however, during each series of experiments. 



Biess indicated the quantity of E collected on the outer coating of" 

 ■ the battery by q. The unit by which q was measured was the quan- 

 tity of electricity imparted to the battery for each discharge of the- 



