f>08 



ELECTRICITY, 



Van Ma- 



nuu. 



neriptiTe forests, and where the trees raise their ' from 



M 7* the surface of the earth, so t! 

 ""*""" * the electric fluid ;it 



elevated; while the sharp < .>f their ! 



boughs, and brand p ntj granted 



them by the munificent hand of \:'tnrc, to draw down 

 from the atmosphere th.it electric fluid which is so pm\ rr- 

 ful an agent in forwarding vegetation, and in promo- 

 ting the different functions of plants." 



The most correct ex|x'rinicnts ujxm this subject have 

 been recrntly made by Van Marum. He emj'! 



uis trees, such as the yung stems of a common 

 willow tree, and he electrified them in the middle of 

 April, when the young br.-inclies usually 'hoot forth. 

 :it shocks through two of these branches, eight 

 feet in length, in the first of them through a space 15 

 inches in length, and in two others through their top. 

 The trees were then planted, but the parts through 

 which the shocks went sent forth no branches. The 

 upper parts through which the shocks had- jjasscd, sent 

 forth a few shoots for some days ; but they came out 

 very slowly, and soon died. Those that were not 

 electrified, sent forth branches like other trees that 

 were planted near them. Hence Van Marum con- 

 cludes, that the effect of electricity upon vegetation is 

 the same as that of lightning. 



Van Marum also made some experiments, in order to 

 poratton of determine if the evaporation of vegetables was increa- 

 Tegeubl". sed by electricity. The pots containing the plants were 

 insulated, and communicated with positive conductors. 

 When they had been electrified for a quarter of an hour, 

 the loss of weight by evaporation was in some cases one- 

 fourth, and in others one-third more than what took 

 place without electricity. Van Marum, however, does not 

 place any confidence in this result, as he supposes that 

 the evaporation may be increased by the current of air 

 from the parts of the electrified leaves. 



This celebrated electrician likewise made experiments 

 on the sensitive plants, viz. the Mimosa puriica, and the 

 Hedysarum gyratu. After exposing the Mimosa pntlica 

 to the sun for the purpose of expanding its leaves, he 

 placed it at the distance of two feet from a conductor 

 positively electrified, and then at the same distance from 

 a negative conductor. No effects, however, were pro- 



On the evs- 



HU expert 

 menu on 

 ttiuitire 

 plants. 



When placed on the conductor, the small leave* 

 rose a little, ..nd expanded when no spark.* \\ 

 from the conductor ; but, when spark i , """ "V" 



ti.e conductor, the 1. . fill. After siiMei 



few changes of this l.ind, the\ began to approach each 

 other, to elosi- theniM l\cs up, and to Ixvomr totally 

 -shut. As thp sair.e ellect was produced by other kinds 

 i.f.slirulis. Nan Marum does n.if think thai they should 

 be ascribed exclusively to electricity. Electricity produ- 

 ced no acceleration or retardation in the motion of the 

 small leaves of the Hi-ili/xaium purans. 



M. A chard of Berlin, made several experiments on Achard* 

 the effects of electricity on the fermentation of vegeta- cxjwri- 

 bles. He took a small quantity of rye, which had been n:Lllt - 

 fermented for the purposes of distillation, and electri- 

 fied one half of it. After tin; lapse of five hour- 

 vinous fermentation was over in the electrified half, 

 while in the unelectrificd half it did not cease till after 

 eight hours. He repeated this experiment, by sending 

 a number of strong sparks through a portion of rye, in- 

 stead of giving it the electrical bath, and, excepting in 

 one case, he always found that fermentation was acce- 

 lerated by electricity. 



See Nollet, Recherchet tur let Causes parficulirrcs drs 

 Phenomenes Electrifies, p. 356', &c. Paris, 174<). Priest- 

 ley's History of Electricity, p. HO. Browning, Phil. 

 Trans. 17*7, vol. xliv. p. 373. Ingcnhousx i'muche 

 mil pflanzen, 1778 1790. Ingenhousz, in Itozier'a 

 Journal, vol. xxxii. page 321, and vol. xxxv. page 81. 

 Schwankhardt, in Rozier's Journal, vol. xxvii. p. 462, 

 vol. xxviii. This paper contains an account of Ingen- 

 housz's experiments, and a reply to the attacks of Duver- 

 nier. Carmoy, in Rozier's Journal, vol. xxxiii. p. 339. 

 Rouland, Dormoy, Bertholon, and Derozieres, in Ro- 

 zier's Journal, vol. xxxv p. 3, 161, 401, and vol. xxxviii. 

 p. 357, *27- Chappe and Mauduyt, in Rozier's Jour- 

 nal, vol. xl. p. 62, 2-tl. Bertholon, De I'Electricite det 

 yegetaux. Van Marum, Tneede Vervol% der Procf- 

 nemingen gedaan met Teyter's Elect. Much. Haarlem, 

 1795, 4to, or in Tilloch's Phil. Mag. Jan. 1801, page 

 314, 318. Achard, Mem. Acad. Berlin, or Tilloch's 

 Phil Mag. vol. iii. p. 52. Kies et Koestlin De Effecti- 

 bus Electricitatis. Tubingen 1775. See also the Histo- 

 ry of Electricity, p. 418. col. 2. 



PART II. PRACTICAL ELECTRICITY. 



Practical I HE various subjects to which we shall have occasion 

 rc"^." to direct the attention of the reader in the present Part 

 "* of the article, may be arranged under five different 

 heads: 



I. On Instruments for collecting Electricity ; 

 II. On Instruments for accumulating and discharging 

 Electricity ; 



III. On Instruments for indicating and measuring 



Electricity ; 



IV. On Instruments for condensing, doubling, and 



multiplying Electricity ; and 

 V. On Instruments for general Purposes. 



BOOK I. 

 lutm- ON INSTRUMENTS FOR COLLECTING ELECTRICITY. 



collecting THE instruments which have been employed for col- 

 eiectridtj. lecting electricity, are of three kinds: I. The electrify- 



ing machine, for collecting the electricity produced by Practical 

 the excitation of electric bodies ; 2. The Electrophorus, Electricity, 

 for collecting the electricity produced by the contact ""V"' 

 of dissimilar bodies ; and, 3. Electrical Kites, Thunder 

 rods, and Conductors, for collecting and discharging the 

 electricity which exists in the atmosphere. 



CHAP. I. 



On the Electrifying Machine. 



THE electrifying machine consists of several parts : Electrify. 

 Of the electric tubstance, which is excited by motion ; j ng ma. 

 of the rubber by which it is excited ; of the amalgam chine. 

 interposed between the rubber and the electric for in- 

 creasing the excitation ; of the mechanism for produ- 

 cing the friction ; and of the }jrime conductor, for recei- 

 ving the electricity as it is generated by the excitation 

 of the electric. 



