OCR Text |
Show 60 Additional Notes. 2. The curious circumstance of electric condensation appears from the violence of the shock of the coJ.ted jar compared with the strongest spark from an insulated conthtctor, tb?ugh the.latter possesses a mL~ch greater su rfacc; when vitreous electnc cthet: JS thrown on one s~de of a coated j ar, it attrac ts the resinous electnc e.ther of the ~ th e r s1de of the coated jar; and the same occurs, when resmous ether ~ ~ thrO\:n on one side of it, it attracts the vitreous ether of the oth er s1de of 1t, and thus the vitreous electric ether on one side of the jar, and the resinous ether on the other side of it b ecome condensed, th a t is ,accumulated in less spac e, by their r eciprocal attraction of each othe r. This contlensation of the two electric ethers owing to their reciprocal attraction appears from another curious eveut, that the t hin ner the glass jar is, the stronger will the charge be on the same quantity of surface, as then the two ethers approaching nearer without th eir intermixing attract each other stronger, and consequently condense each oth er more. And when the glass jar is very thin the r eciprocal attractive powers of the vitreous and resinous eth er at tract each other so violently as at length to pass through the glass by rupturing it, in the same manner as a less forcible attraction of them ruptures and passes through the plate of air in the production of parks from the prime conductor. As these two ethers on each side of a charged coated jar so power· fully attract each other, when a communication is maue between them by some conducting substance as in the common mode of di sch arg ing an clectrised coated jar, they r eciprocally pass to each ot her fo r tbe purpose of combining, as some chemical fluids are known to do ; as when nitrous gas and oxyg en gas are mixed together; whence as these tluids pass both ways to intermix with each other, and th en explode ; a bur appears on each side of a quire of paper well pressed togeth er, when a st.rong electric sTwck is passed through it; which is occasioned by their explosion, like a train of gunpowder, and consequent emission of some other ethereal fluid, either those of heat and li ght or of some uew one not yet observed. Whence it becomes diff-i cult to ex plain, according to the theory of Dr. Franklin, which way the e lectric fluid passed, and which side of the coated jar contained positive and which the negative charge according to that cloctrine. Chemical Tlzeury qf Electricity and Magnetism. 61 B.ut the theory of the ingenious.Dr. F.ranklin failed also in explaining othet phenomena of the coated Jar· smce 1'f the ·t· 1 · · . . ' post Ive e ectnc1ty accu_mulatecl on one Side of the jar repelled the electricity from the coatmg on the other side of it so as to produce an elect · 1 · ' nc vacuum; w lY sho_ulc~ It be so eage~·, wh en a communication is made by some C01~ductm g. body, to run mto that vacuum by its attraction or gravit~ tJOn, wh1 ch has been made by its repulsion; as thus it seems to be vwlently a_ttra.ct~~~ by t.he vacuum, from which it had previously repcll ~d a fhud s:mtlar to Itself, which is not easily to be comprehended. :.> •. There Is. anoth er mode Ly which either vitreous or resinous elect~1c ether 1s capable of contl ensation; which consists in contractmg the volume, so as to diminish the surface of the electrised body;. ~s was. ing eniously shown by Dr. Franklin's experiment of electnsmg a Sl!ver tankard with a length of chain rolled up within it; and then drawmg up the chain by a silk st ring, which weakened the el e ctri~ attraction _of .the t~nkard; which ~vas strengthened again by returnmg the cham 1nto 1t; thus the con<.l ensation of an elcctrised cloud is beli eved to cond ense the electric eth er, which it contains and thus to occasion the lightning passing from one cloud to anothe;·, or from a cloud into the earth. This experim ent of the chain and tankard is said to succeed as well with what is t ermed negati ve electri city in the theory of Dr. Franklin,. as wi th what is termed positi\re elec tri city ; Lut in that th eory the neo·a~ tive electri c ity means a less quantity or total deprivation or vacuity0 of that fluid ; now to condense negat ive electri city by lowering the suspend ed chain into the t ankard ought to make it less negative ; whereas. in this ex perim ent I am told it becomes more so, as appears by its stronger repuls ion of cork baUs suspend d on silk strings, and previ ouslyelcctrised by rubbed sealing wax : and .if the negative el ectri city be believed to be a perfec t vacuum of it, the cond ensation of a vacuum. of elec tri city is totally i ncomprehcnsiblc; and this experiment alone seem to demonst rate the existence of t wo electric ether . |