Whether there is surface resistance 287 



By the mean, the resistance of 1-3 of distilled water = that of 23^ of mixed. 



10-9 inches of tube 5 in the place where used holds 120 grains of $, or 37 

 inches holds 408 grains, which is the same as tube 8: therefore the resistance 

 of distilled water is 18 times greater than that of mixed, or 702 times greater 

 than that of a saturated solution of sea salt. 



578] Whether the electricity is resisted in passing out of one medium into 

 another in perfect contact with it. 



The Qth tube of P. 126 [Art. 575] was filled with 8* columns of saturated 

 solution of sea salt inclosed between columns of , the end columns being 

 The tube 7 was filled with one short column of at the bent end, and a long 

 column of saturated solution of sea salt. 



It was found that the shock of one jar, charged till the straw electrometer 

 separated to i-o, passed through a column of the salt water in tube 7, 



' [ inches long, was rather j diminished than in passing through the 



mixed column in tube 9, the wires used in tube 9 being immersed in the end 

 columns of , and those used in tube 7 being immersed one in the short column 

 of $ at the end and the other in the column of salt water. 



The length of the mixed column in tube 9 was 43-5 inches, its weight was 

 10-5, the weight of a column of of the same length was 18-10, therefore the sum 

 of the lengths of all the columns of salt water was 21-8 inches, and by the 

 experiment the shock was as much diminished by passing through 24-4 inches 

 of salt water in tube 7 as through this. But as the bore of tube 7 in that part 



which was used was greater than tube 9 in the ratio -- ' x = 1-06 to i 



22-3 37'4 



nearly, the shock should be as much diminished in passing through a column 

 22-94 long in tube 9 as through one of 24-4 in this. Therefore the shock is as 

 much diminished in passing through a mixed column, in which the length of 

 salt water is 21-8 inches, as through a single column of the same size whose 

 length is 22-94 inches. 



The difference is much less than what might proceed from the error of the 

 experiment. 



579] A slip of tin was made consisting of 40 bits soldered together, all 

 i\i inch broad and all about \ inch long. They were made to lap about ^ inch 

 over each other in soldering. I could not perceive that the shock of a jar was 

 sensibly less when received through this than through a slip of tin of same 

 length and breadth of one single piece. 



If the jar were charged pretty high and a double circuit made for it, namely 

 through this piece of tin and my body, I could not perceive the least sensation. 



580] Made at Nairne's with his large machine. 



A long conductor was applied to the electrical machine and a smaller con- 

 ductor to its end, a Henly's electrometer was placed on the middle of the long 



* [8 in MS. Perhaps 80.] 



