404 



RECENT PROGRESS IN PHYSICS. 



gradual approach of the other knob of the micrometer. One experi- 

 ment gave, for instance, the striking distance 1.475 lines. 

 ;:; The movable knob of the spark micrometer was then shoved back, 

 the plate B charged in the same manner as before, and the disk A 

 placed erect and brought within two lines of B ; B now acted induc- 

 tively on A, — E collected on A,* and reacting inductively upon B, 

 brought about another arrangement of the electricity in the system 

 opposite to it ; the electricity collected more in A, and its density on 

 the knob C is diminished ; from this follows a reduced striking dis- 

 tance ; for on bringing up the other knob of the spark micrometer 

 until a spark passed, the striking distance was found to be 0.150. 

 By the approach of the condenser, therefore, the electricity is accumu- 

 lated upon A ; its density on C on the contrary, is diminished, and 

 Fig. 44. in the propor- 



tion of 1.475 to 

 0.150, or in the 

 last case it is 

 only 0.102 of 

 the former. 



The electri- 

 cal charge, 

 which the jar 

 gave to the 

 plate was not 



perfectly equal in both cases, for beside the loss of charge which the 

 jar suffered between the times of the first and second contact, it had 

 imparted electricity to the plate at the first contact, hence at the sec- 

 ond its charge must have been somewhat, although but a trifle, less 

 than before. In order to correct this inequality in the quantities of 

 electricity, Riess made a series of experiments, alternately with and 

 without the condenser, and compared the striking distance of each 

 experiment with the mean of the preceding and following ones. The 

 results are arranged in the following table. Distance of the plates, 

 two lines : 



•-■Throughout his whole memoir ifi'eis avoided the expression ^'■hmind electricity," [gehun- 

 deue (lectricitat,) for no other reason than because a false idea was connected with it. This 

 term may be very properly united with a correct conception, and consequently I do not 

 think an expression should be proscribed which has gone so much into common use. 

 False conception of " bound," i. e., disguised electricity, are not so generally disseminated 

 as Riess seems to think ; I never had any other view, than thp-t which he presents, and he 

 can hardly find much to object to in the presentation of the matter in my Treatise on 

 Physics, unless he should take offence at a single word ; the remark on the lower half of 

 page 414 of the first volume of the first edition, (3d edition, 2d vol., p. 97,) are designed 

 to remove every doubt as to the true meaning, and yet at the time I wrote that part, the 

 memoir of Hiess and the whole controversy on the nature of disguised electricity, was un- 

 known to me, else I would have certainly suggested the proper experiments described in 

 Section 17 of this report, and I also would have avoided here and there a few less ac- 

 curate expressions, which, as I was not aware of any controversy, were used quite tiu- 

 designedly. 



£See note at the commencement of this Section ] 



