[LM111010], Letter from Arthur Edwin Kennelly to Thomas Alva Edison, July 27th, 1888



The following are the results of one ---- of Mr Marshall condenser yesterday####The greatest discrepancy between the two blocks is between no (9) 0.0995 and mos (5) + 17 each 0.10015 c a offer of 0.0008- c or 0/65 nearly 2/3rds) %. That is a ---- discrepancy. The mean discrepancy is 0.25%####Between the sum of the - 1/10th mi---- and the unit [muero?] there is a discrepancy of --- % ####Between the two miers block and the one miers block there is a discrepancy of 0.38%####The differences between the different blocks of our standard Elliot condenser are less than these, but still the adjustment must be called first.#### The agreement between Mr Marshall's ondensers as a whole, and over Elliot standards is written 0.38 % throughout, his being greater than this Elliot capacity to about that extent.####The insulate of Mr Marshall's condenser is good It loses 1.9% of it charges in 5 mins and 10% (app--se) half charge in 380 mins and this corresponds to a calculated insulation of 8.230 [megohms?]####[Third page]####I---- similar conditions on Elliot standard lost 2.3% of its charge -- 5 mins. 12% in 45 mins, with a calculated corresponding fall to half charge in 244 min and an insulation of 5290 a####I think that we did not take so much pains to insulate and dry our Elliot standard which we know to be good, as we did with Mr Marshall's which we send to [consumer?], but under the conditions the insulation of Mr Marshalls is over 50% better than the of the Elliot.####On due consideration I do not prefer Mr Marshall's plan of having different combinations obtainable in series. It is more complicated and requires more time and thought than the ordinary arrangement. Nor is the saving in blocks more than an apparent one, for on the principle of subdivision used by the Elliot f----, it is possible to have any combination to three decimal places of capacity between 0.001 c and 4.000 - ---- 14 blocks, while Mr Marshall does the same with 12 blocks and a little more pl-- insertion to each. Further, a standard condenser is not intended for rogh work but for acccuracy, and to obtain accuracy an observer well sometimes require to know the exact ---- of each block in the condenser he uses On the Elliot multiple are plan this is a matter of summing. On the Marshall series plan the complete error is only arrived at after considerable calculation. As an observer I should prefer to use the Elliot incitement, as a maker I should prefer to make them on the Marshall principle








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[LM111010], Letter from Arthur Edwin Kennelly to Thomas Alva Edison, July 27th, 1888

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Thomas A. Edison Papers, School of Arts and Sciences, Rutgers University