3B+C+2A=(9.2) commun. to 1 row, 2 passed through 2 loops, once missed, once did not pass through 3, never through 5. R communicated to 7 rows = 20.6 was tried 3 times without ever passing through 3 rows. Wed. May 31 [1775]. 606] 1 jar was elect. and commun. to 1 row of battery, and shock taken without torpedo. There seemed a little difference in the strength of the shock according to which row it was communicated to, but hardly more than was observed at different times from the same row. Result of exp. May 30. 607] By mean, quant. el. req. to give same shock with 7 rows is to that with 1 :: 18-3: 11·5 :: 1·6 : 1†. water. 608] The 2nd leather Torp. was tried in sand wetted with salt The Torp. lay flat on sand and was covered by it all but pos. elect. parts & middle of back. With 3 rows charged to 11, felt a shock whether I laid bare hands on torp. & on sand 16 inc. dist. from nearest part of Do. or whether I touched torp. with metals. In latter case shock seemed much the same as shock 10 inch plate crown glass § received 91 through Lane's el. at 1600 inc. If I laid pieces of sole leather|| which had been soaked in salt water for a week and then pressed between paper with hundred weight for * [Arts. 433, 605.] S[Arts. 411, 430.] + [Arts. 406, 573, 610, and Note 31.] 610] SHOCK THROUGH SALTED WOOD. 317 day to drain out moisture on torp. and on sand, and received shock with metal that way, shock was about equal to that of 10 inc. plate with 61 Lane at 1600' The torp. taken out of sand and tried with metals in usual way gave shock about equal to D° plate, Lane at 183. Being tried in same manner with 1 row, shock was weaker than in sand through leathers, & with 2 rows stronger than without leathers. The spe. gra. bottle with water which came from sand weighed 8.4.11. Th. at 69, so that the water with which it was moistened appears to be of right strength. 609] Bits of beech, wainscot & deal* about inch square were soaked in salt water for 3 or 4 days, then taken out and wiped and exposed to the air in dry room for about 6 hours. The shock of the Torp. was received touching pos. el. part with metal and neg. with one of these bits, the end which touched the torp. and that part which I held in hand being bound round with tin foil. With 6 rows elect. to 1, I felt slight shock through wainscot: dist. tinfoils 2 inc. With Do charge through deal, tinfoils at 1 inc., none. With 3 rows to 1; received shock through beech, tinfoils at 4 inc. dist., about as strong as with 1 rows when touched with metals on both sides. With Do charge through 4 inches of dry deal dipt in salt water and tried the instant it was taken out, none. Taking hold of tail in one hand & touching pos. side with metal, brisk shock. When touching neg. side with metal much slighter, the exper. tried with each pos. and each neg. part. Mon. June 12 [1775]. 610] Jar 1 elect. to 21 by pith el. seemed to give shock of same strength as B+ 2A comm. to whole battery; it was weaker than 2B and stronger than B commun. to Do, but as there is a good deal of difference between the sensations of the 2, it is not easy comparing them. According to this exp. the numb. jars which el. should be divided amongst in order to produce given shock should be as the 27 power of quant. el., and therefore el. 2 jars should be comm. to 5 more in order to produce same shock as 1 jar t. * [Art. 588.] + [Arts. 406, 573, and Note 31.] Mon. June 18 [1776 *]. IR + 3B + C + 2A comm. to 7 rows = (341), & el. to a given mark on pith el. gives shock equal or rather greater than 1 row el. to same degree and not commun. to rest. 1R + 3B + C + 2A elect. to 1 on straw el. and comm. to rest always passed through 1 loop of machine. The same elect. to 1 sometimes passed, sometimes failed. 1 row charged to 1 and not commun. to any more passed 3 times through 5 loops without once failing. IR + 3B + C + 2A el. to 1 and comm. to rest would never pass through 2 loops. 611] 2nd Leather torpedo tried under water with metals with glass tubes on them, all rows charged to 4 gave briskish shock, which was much greater than shock out of water with 1 row to 1, but rather less than with 2 rows to Do. The shock received in same manner with 1 row not communicated to rest was less when el. to 1, and about equal when el. to 21. With 7 rows el. to 1 shock of D° Torp. when received through the salted lime tree wood gave slight shock about equal to 3A passed through same wood without torpedo. Charge of 7 rows el. to 4 is to that of 1 row el. to 1 as 7 x 2.8 : 1 :: 12 to 1. 13 612] Tu. July 4 [1775]. 2nd leather torp., the wire belonging to convex side fastened to outside of battery and inside of battery touched by wire of flat side. Under 3 rows of battery charged to 1 and comm. to remainder. water no sensible diff. whether I touched convex or flat side with one hand. Out of water, touching tail with one hand and one side of one elect. organ with metal, a much greater shock if I touched convex side than flat side. The event was the same if it was elect. by neg. elect. Touching convex side of both organs with one hand only, standing on electrical stool, a shock in that hand, but I think scarcely so strong as under water. Touching flat side in same way, much the same. Laying 1 finger on convex surface of one organ & another finger of same hand on the middle of the convex surface, a very slight shock. [Probably June 19, 1775.] 614] CAPACITY OF REAL TORPEDO. 319 Laying one finger on convex surface of one organ & the other on the nearest edge of the torpedo, a considerably greater shock, but not strong. Laying one finger on convex and another on flat side of same organ, a considerably greater shock, but do not know how to compare it in point of strength with that taken the usual way. Tried without any torpedo *. 613] 3B being comm. to 7 rows and passed through 1 loop of 26 links of small chain. If the chain was not stretched by any additional weight, the shock did not pass. If the middle link was stretched by a weight of 7 pwt. it passed, & the light was visible in a few links. If it was stretched by a weight of 13 pwt. no light was seen. There was no remarkable difference in the strength of the shock, whether it was received through chain tended by 13 pw. or without chain. The chain was fastened to the same machine that was used in a former experiment, it was 7.9 inc. long and the distance of the supports 5.1. The room was quite dark, it being tried at night without any candle in the room. 3 rows of battery were elect. till pith el. sep. to 1, its el. was then comm. to the rest of the battery, & I received the shock of 1 row, the elect. having its choice whether it would pass through my body or through some salt water. I then elect. 1 row of battery till pith el. sep. to same degree, and commun. its elect. to rest of battery and received the shock of 5 rows of it in same manner. The shock seemed to be nearly of same strength, perhaps rather less. Therefore shock of 5 rows elect. to a given degree seems about equal or perhaps rather less than that of 1 row el. to 3 times that degree. 614] The mean thickness of the section of the elect. organ in the section given in Mr H. † paper, in which the breadth is 10-3 inches, that is, the same as my torpedo's, is 1.3 inc.; the area of one organ is 121 2.5 × 51 × 9 sq. inc., as found by cutting out a piece of paper 15 of that size and weighing it. And according to Mr H. there are about 150 partitions in 1 inch, therefore comp. charge both organs reckoned in old way is 19 × 1.3 × 150 × 1 × 150 = 748000, and the real charge is 1122000 inches of el. supposing the par [Art. 437.] +[Anatomical observations on the torpedo. By John Hunter, F.R.S., [Phil. Trans. 1773]. Art. 436.] titions to consist of plates of white glass inc. thick, which is about 2 times as much as my battery, that being = 451000 inc. el. 615] Tried with the 2nd leather torpedo, new covered, in large trough full of water, the torpedo laid flat as in figure, the electrical organ being (as supposed) 3 inches under water. was just sensible in elbow. If torpedo was tried out of water with 1 row to 1 comm. to 7 and touched with hands in usual manner, the shock was just felt in hands, and if touched with metals, Tried under water in above-mentioned manner with 7 rows el. to 4, the upper surface being touched with the pestle of a mortar held in one hand, the other hand dipt into water as far as wrist, a shock in the wrist of the hand in the water I believe full as strong as the former. The place where the hand was dipt into water was about 11 inc. from the front of the fish, and conseq. about 14 from elect. organ. Tried in the same manner as before, except that the fish lay in an open wicker basket*, just big enough to receive it, and which had been soaked for some days in salt water. The shock seemed much the same. Holding hand in water in same manner as before without touching torpedo-no sensation. With three rows to 1 out of water, the shock was stronger if I touched convex side with one hand laid flat on elect. organs than if I touched flat side in same manner, but the difference was not great. Charge of 7 rows el. to 4 is to that of 1 row el. to 1 as 19.6 to 1. The water appeared by its spe. gra, to contain of salt. 31 * [Art. 421.] |