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VI. " On Quantitative Measurement in Statical Electricity, 

 and on some new Phenomena of Electrical Force." By Sir 

 WILLIAM SNOW HARRIS, F.R.S. Received June 12, 1856. 



(Abstract.) 



The author observes, that number, weight, and measure are the 

 foundation of all exact science, and that, as expressed by an eminent 

 and learned writer (M. Quetelet), no branch of human knowledge 

 can be held as being out of its infancy which does not in some way 

 or the other frame its theories or correct its practice by reference to 

 those elements ; he was hence led to seek and establish such rigorous 

 and exact quantitative processes in common electricity as would mea- 

 sure the quantity of electricity in operation ; its attractive or repul- 

 sive force under given conditions, and its dynamical or current force 

 when traversing bodies under the form of electrical discharge. The 

 instruments which he has invented for this purpose have been all 

 honoured by a place in the ' Philosophical Transactions of the Royal 

 Society.' They amount to five in number, viz. the Unit Measure, 

 the Balance and Hydrostatic Electrometers, the Thermo-electrometer, 

 and the Bifilar Balance. In referring to such of these instruments 

 as are employed in the present research, the author briefly adverts 

 to their general construction, including the latest and best form 

 under which they have been placed. 



In the measurement of quantity, he considers the unit measure as 

 being the best and most accurate means of estimating quantity as yet 

 arrived at ; and he describes a series of crucial experiments, the object 

 of which is to show that the unit explosions are rigorously exact. If 

 an electrical jar exposing about 5 square feet of coated surface be in- 

 sulated, and a second equal and similar jar be so placed as to charge 

 from its outer coating, and if the first jar be charged from the con- 

 ductor of the machine through the unit measure, it is found by a 

 Lane's discharging electrometer attached to each jar, that an equal 

 number of measures are given off from the outer coating of the in- 

 sulated jar at all periods of the progress of the charge. Thus, 

 whether the first jar be charged with 20, or 40, or 60 measures, 



