22 A. M. Mayer on '•Hhe electro-ionic state." 



current or wave of electricity which shall always have the same 

 intensity. The following apparatus combines these require- 

 ments in an eminent degree. Twenty-five spirals (such as are 

 described in my papers in the Sept. and Nov., 1870, Nos. of this 

 Journal) were placed between twenty-live similar spirals, so that 

 each alternate spiral belonged to the same circuit. The termi- 

 nals of the first series of spirals were connected with a galvanic 

 battery, while those of the second combination were connected 

 with a spiral similar to one of those described in the paper "on 

 the measurement of electrical conductivities," in the Nov., 1870, 

 No. of this Journal. This spiral was placed on a magnet, about 

 3 ins. distant from its end, so that by suddenly slipping it otf a 

 current could be produced in the secondary wire without the 

 interposition of a liquid. By interchanging the connections of 

 the terminals of this spiral, an inverse current could be produ- 

 ced on sliding it off. A reflecting-galvanometer, reading deflec- 

 tions to 15", was also placed in the above circuit. 



If the spiral is always removeil from tlic suiiu; Icngtli of mag- 

 net with the same velocity, it iK'cr.^sui'ih- lolNnvs— 111.' (;ircum- 



stances in each case being alike tliat sn.ci's^ivr cnrrcuts of 



equal intensity will traverse th.^ sicMinlaiv wiiv. This con- 

 stancy of velocity in all tiic .■xprTinicnt- cai'i be; j^rwduccd in the 

 following manner. The mauiK't was [ilar.d vertically, N. pole 

 downward, and the tcnuiu/ils i,!' the spii-al which were 18 ins. 

 in length, were eoun.cted with the <Mnl> ..1 aevliiider of copper, 

 transversely divided }jv an insulatin-- disc of ebonite. Each 

 end of this horizontal cylinder rested on a V, and a close 

 contact was ensured by amalgamation. The spiral was now 

 allowed to fall off the magnet, and as it always made this move- 

 ment with the same velocity, it followed that currents of equal 

 intensity were produced during each fall. It was however found 

 that currents of such equality of intensitv were produced, by 

 quKhly slipping off the spiral, that the range of their differences 

 did not exceed 20" in the deflection of the needle of the reflect- 

 ing-galvanometer. In the experiments which follow, I used 

 the currents produced by quickly removing the spiral from the 

 magnet. This ready method of producing at will an electric 

 current or wave of any required intensity, seems to me will be 

 of value in many electrical researches, for I have found that 

 any current, produced by chemical means, fails in cmstancy 

 when its intensities are measunMl bv a ivlleetiri<>-<'alvaiiometer, 

 though by the or linarv iiistrmiatit it'inav api.rai'so. ' 



In the apparatus thus arraii<'v<l w InVi' \ rui'ubirririoii of 25 

 spirals, containinq ?,^u feet of"'^ i„..h r!,,,..-',- wiiv ii', proxin»itv 

 to a combination ot 2.1 sin,ilar%pira!s \ ,-u,Tent wa^ "; 

 through the first spirals, of such a stn'iiLith that the n-' 

 in the battery equalled the e)utside resi<taiie..< ii, the s^.i!; 



