Spreading of electricity 261 



537J Crown with slits and H with D compared with white cylinder; and A 

 and C with oblongs compared with B *. 



The coatings were taken off from the plates A and C and oblong coatings 

 without slits put in their room. The coatings were also taken from the crown 

 glass, and oblong coatings with slits like those put to C put in their room. 



Fr. Feb. 12 [1773]. Th. 49. N. 

 [34 observations, Art. 660.] 



538] Experiment of p. 61 [Art. 535] tried with small ball blown to the end of 

 a thermometer tube. 



A ball rather less than | inch diam. was blown at end of glass tube and was 

 coated on outside with tinfoil, the inside being filled with $. This was used 

 instead of plate D in exper. to see whether charge of Leyden vial bore the 

 same proportion to that of another body whatever force it was electrified with. 

 It was found that 12 inches of this tube when coated contained as much el. 

 as K + jj^D, and therefore the spreading of the el. ^ inch on surface of this 

 tube increases its charge by ^%D, whereas the spreading of el. ^ on surface 



of D increases its charge by j D. 



5s 



Th. 49. N. 13$. Tin plates at 17 inches from wire. 

 With electrometer at I + 3. 



Div. on 

 sliding plate 



4 22 



3 3i 



3 ' 6 



4 *9i 



sep. about i diam. pos. 

 D neg. 



With electrometer 

 DO 

 D 



Sum. 



32-1 



32-2 



Fringed rings on plate of crown glass &c. f 



Sat. Feb. 13 [1773]. 



It was found on looking at the plate of crown glass that there were narrow 

 fringed rings of dirt all round the edges of the coatings, the space between these 

 rings and the coating being clean. This was supposed to be done by the ex- 

 plosions. 



The distance of these rings from the edge of the coating seemed nearly the 

 same both within the slits and without, but of the 2 seemed less within the 

 slits. The mean distance seemed about -105 inc. which seems to shew that the 

 electricity spreads pretty nearly the same both within the slits and without. 



'Something of this kind has been frequently observed in the sliding trial 

 plate i and sometimes I believe in some of the coated glass plates. 



Sun. Feb. 14 [1773]. Th. 49. N. 17. Last exper. repeated. 

 [At 1 + 3, Sum = 29-6, at 3 + i, Sum = 28-3. Plate D gave 26 and 27-5 

 respectively. See Art. 664.] 



* [Art. 321.] f [Art. 308.] 



