358 Sir W. Snow Harris on a General Law of 



only furnishes a rough, an inexact measure of the quantity of 

 electricity" — " The method employed by Harris in the Philo- 

 sophical Transactions for 1834 is still worse." Losing sight of 

 all the novelty and philosophy of my simple and useful little 

 instrument, M. Riess treats it as a mere casual employment of a 

 Lane's bottle, and then proceeds to apply to it some rather com- 

 monplace and unsound objections. Yet in following out my 

 arrangement of an insulated battery with a Lane's electrometer 

 jar in connexion with the outer coating (17), M. Riess really com- 

 promises his own principles. If, as he states (PoggendorfF's 

 Annalen, vol. xl. p. 323), " a bottle is more completely charged 

 when there is no obstruction to the action of the outer coating," 

 then if my unit jar be inaccurate on this ground, surely the Lane's 

 bottle dignified in M. De la Rive's work with the title of " Bou- 

 tcillc electrometriquc," directly interposed between the outer 

 coating of the battery and the earth, must be necessarily at 

 least an equal obstruction to the charging of the battery. The 

 fact is, that there is little or no obstruction at all in either case. 

 The unit jar neutralizes at each explosion, and each discharge 

 must correspond to an equal quantity of electricity accumulated 

 in it. This must be so on the principle long since established 

 and admitted by M. Riess himself, viz. that the quantity of elec- 

 tricity accumulated in a jar will be as the distance of the discharge 

 direetlj"^, all other things being the same. Now submit the unit jar 

 to this experimental truth. Attach a Lane's electrometer to ajar 

 exposing about five square feet of coating, or to a battery of 

 smaller jars; set the balls to given measured distances, say to 

 successive distances which are to each other as 1 :2. Here it will be 

 found, if the experiment be carefully made, and there is no dissi- 

 pation of the charge, that at twice the distance twice the numbfr 

 of units as measured by the jar will correspond with the great 

 explosion of the large jar. But how could this happen if the 

 quantity represented by twice the number of discharges of the 

 unit measure was not double the quantity represented by the 

 number of explosions or discharges taken as unity ? Faraday, 

 one of the best authorities on such questions, has, upon a full 

 consideration of the subject, acknowledged the accuracy of my 

 views*. So far from this method being open to the doubts 

 which ]\L Riess has thrown upon it, it will really be found much 

 more accurate than the method of insulathig the battei-y, which 

 is only a clumsy way of eifecting the same thing. The large open 

 surface of an insulated battery is always liable to give off elec- 

 tricity in other directions than that of the " bottle of measure," 

 and we are always at the mercy of the insulations. 



27. If we turn to Poggendorff's Annaleny vol. lii. for 1841, 

 * No.id, Manual of Electricity, p. 141. 



