523] FLASK CHARGED A LONG TIME. 261 522] Computed power of above flask. The diameter of the flask at the surface of the water in tin pan on Saturday was 17; the height of that part above the bottom 5.1; the height of top of tinfoil coating above bottom 6.55; and the diameter of that place, 68; and the circumference at the widest part 13. The weight of that part under water was 1..2.. 7*, and that of the part between that and the top of coating was 2.. 4. If the spheroid agdm does not differ much from a sphere, and ab does not differ much from ad, the surface afea is nearly equal to the circumference (surface 2ab+gm the thickness of of gm × ab × 2 3ab (comp. pow. 62 power of the whole part below top of coating 6575, the specific gravity of the glass being supposed 2-68. Therefore inc. el. by comp. pow. = 1.78. 523] As it appears from the above experiments that the Florence flask contains more electricity when it continues charged for a good while than when charged and discharged immediately, it was tried whether the white globes would do the same. This was done by putting the globe 3 on positive side and the white cylinder and trial plate 6 on negative side, and first charging and discharging them in the common manner, and then discharging the magazine and charging it again, while the end c of the wire Ce rested on Bb, while the end C was prevented from resting on Aa by a silk string. When the magazine was charged, and had continued so for a little time, the end C was let down on Aa and the wire Cc immediately drawn up again so as to discharge the globe &c. The event was as follows, By these experiments the globe contains 45 inc. el. or about less when electrified in the common way than when charged before the rest, which is as much as is contained in 1 inch in length of the uncoated part of the neck (the whole neck being 1 inches), so that supposing the experiment exact it seems as if the globe contained rather more elec [Troy weight.] tricity when it continued charged a considerable time than when charged and discharged immediately *. 524] Diminution of shock by passing through different liquors †. Tried in November [1772]. The electricity was made to pass through 42 inches of a saturated solution of sea salt in a thermometer tube of a wide bore, and the two jars charged in such manner as that a slight shock should be felt in [the] elbows: it was then made to pass through rain water in a tube of a rather greater capacity, and the electricity made rather stronger. The wires were obliged to be placed within 18 of each other in order to feel the shock in the same degree. Therefore the electricity meets with more than 230 times the resistance in passing through rain water than salt. The above jars were electrified till light paper cylinders began to separate, and the shock made to pass through a tube filled with rain water. The wires were obliged to be brought within 48 inches of each other in order that the shock should be just felt in the elbows. When the same tube was filled with saturated solution of sea salt diluted with 29 its bulk of rain water, a much greater shock was felt when the wires were at 16 inches from each other. Therefore electricity meets with much more than 34 times the resistance from rain water than from a saturated solution of sea salt with 29 of rain water. When the same tube was filled with kitchen salt in 1000 of rain water, the wires must be brought within 44 inches; with pump water within 2 inches, and with spirit of wine almost close; therefore the resistance of Pump water is (4 less than that of rain water. S. salt in 1000 of rain water) 19 Mon. Nov. 16 [1772] with straw electrometer. With sea water a shock was felt when the wires were 19 inches distant; with rain water when they were at about 19 inches distant. Therefore resistance of sea water is about 100 times less than that of rain water. 525] Exper. Whether force with which two bodies repel is as square of redundant fluid in them. * [These phenomena are connected with the 'residual charge.' A careful investigation of them has been made by Dr Hopkinson, Phil. Trans., Vol. 167 (1877), p. 599.] [This is the first experiment on electric resistance.] [Arts. 386, 563, 567.] 525] REPULSION AS SQUARE OF REDUNDANT FLUID. Tried by pith balls hung by threads. 263 A and B are the coated plates A and B, the bottoms of which communicate with the ground, D and d are two bits of wood resting on them, supporting the pith balls E and e. G is a bit of wood for making a communication between them. The wire for electrifying the plates rests on B, and is so contrived that when that is lifted up the wood G is let fall on the plates. The pith balls E had bits of wire made to run into them in order to increase their weight. A paper with divisions was placed 6 inches behind the pith balls and a guide for the eye 30 inches before them. Tu. Oct. 26 [1773]. Th. 60. Com. - 6. N. 21. One of the balls E with its string weighed 5 gr. and its wire 14, the other '6 gr. and its wire 1·7. The two balls and strings together the weight of one of the strings weighed 105 gr., the weight of the string about '05, the weight of the two wires together was 3.2. When the wires were taken out of the balls E, and a communication made between the two plates, while the electrifying wire rested on B, then when balls e sep. balls E sep. 1.14 * (1.25 (1.2 The wires were put into balls E and the jars electrified while the electrifying wire rested on B. When the balls E sep. 1.3 inc. the electrifying wire was lifted up and the electricity of the plates taken away, immediately after which the electrifying wire was let down and immediately drawn up again when the balls e separated to 1·44. The electrifying wire being then let fall on B and suffered to remain, the balls E separated to 1.14. The jars were charged, and the electricity diminished by alternately drawing up and down the electrifying wire and discharging the electricity of the plates till the balls e separated to 1-2; then letting the electrifying wire rest on B, the balls E separated to 1.08. Wed. morn. The new heavy electrometer made with large wood ball and pith ball separates when the balls E separate to 1·52, and new light electrometer separates when the balls e separate to 1·44. When balls e separate to 1.44, balls E separate to ‘96. The new heavy electrometer above mentioned separates about or 1 inch when old light cylinder electrometer just separates. Result of these experiments. Balls E without weight separate farther than balls e with the same degree of electrification. If balls of given weight separate 15 with given degree of electrification, balls of 4 times weight separate 96, therefore if balls of given size are electrified in given degree, the distance to which they separate Therefore, in last paragraph, if balls of given weight separate 1.9 1.22 1.5 1.25' balls of 1.57 their weight will separate to 108, therefore if balls of given weight with given quantity of redundant fluid separate to given •475 distance balls of that weight separate to same distance with half that quantity of redundant fluid. 526] Whether the charge of plate E bears the same proportion to that of another body whether the electrification is strong or weak: tried by machine for Leyden vials. Wed. Oct. 27 [1773]. Th. 61. Com. 81. N. 201. Plate E of Nairne on neg. side against sliding tin plates placed at end of long wire [20 observations]. Result. Therefore with light electrom. the plate E is balanced The plate E is balanced by 37 inc. el. 527] Plain wax and 3rd dephlegmated wax with E + F and 5th rosin with double plate A and B. Also small ground crown with D + E + F, and large do. with C. The coatings were taken off from 4th rosin, and coatings 179 inc. diam. put in their room. This is called 5th rosin. A plate of dephlegmated bees wax was also made [120]* inc. thick and coatings put on 3-525 inc. in diam. This is called 3 dephlegmated bees wax. A plate of plain bees wax was also pressed out [119]* inc. thick and coatings put on 3.475 inc. diam. * [These measures are left blank in the Journal. I have supplied them from Art. 371.] 533] LIGHT ROUND EDGE OF COATING. 265 A piece of thick crown glass was procured from Nairne about 26 thick and ground down equally on both sides to about 07 inc. thick. Two circular coatings were put on, one 3.54 inc. in diam. the other 2.035. Wed. Jan. Th. 56. N. 27 [16 observations]. 528] K, L and M compared with D + E + F at distance and close together; also large ground crown with C and small one with D + E + F ; also 3rd dephlegmated wax and plain wax with E+ F; also 5th rosin with double B. Friday, Jan. 29 [1773]. Th. 33. N. 161. Tried with middle sized cork balls and a new white large trial plate [18 observations. Art. 656]. 529] K+L+M compared with A, B, and C; also A + B + C with H. Sat. Jan. 30 [1773]. Th. 50%. N. 16. [20 observations. Art. 657.] 530] K+L+M compared with B with electrification of different strengths. Sun. Jan. 31 [1773]. Trial plate F enlarged. [14 observations with light and heavy electrometer alternately. Art. 656, 658.] 531] K+L+M with A, B, and C; also D + E + F with K, L, and M; also small ground crown with K, L, and M; and D + E + F and large ground crown with A, B and C and K+L+ M. Mon. Feb. 1 [1773]. Th. 48. N. 16. [20 observations. Art. 657.] 532] On light visible round edges of coated plates on charging them*. Mon. Feb. 1 [1773]. Th. 48. N. 16. Some coated glass plates were placed on pos. side and electrified in usual manner in dark room in order to see whether any light was visible round their edges. With the plates M and L of Nairne and with the small ground crown glass a light was visible round the edges when the light electrometer was used, and nearly equally so with the large ground crown glass. The light seemed of the 2 rather stronger with the plate F and A of Nairne; no light was visible when light electrometer was used, but it was with the heavy electrometer. 533] Crown A and C and large ground crown with C; also 3rd dephlegmated wax, plain wax and sliding plate 3 with E+ F; also 2 double plates with E, F, and D. * [Art. 307.] |