62 



NA TURE 



[May 17, 1883 



was similar to the one at Oratunturi, but the galvano- 

 meter here was not so sensitive, as the needles had lost 

 some of their astatic quality through the journey. 



On December 29 there appeared above this apparatus 

 a single column of aurora some 1 20 metres in height .' Its 

 plane was determined from several points, viz., S.S.W. to 

 E.S.E., within an angle of 90° with the plane of the 

 horizon, and there was not the slightest doubt of the 

 aurora appearing just above the apparatus. No spectrum 

 analysis was, however, made, as the question of the 

 greatest moment on this occasion was to determine the 

 plane of the column in relation to the apparatus. A faint 

 aurora in the sky at the back of the mountain might 

 perhaps have influenced the analysis ; besides which 

 another difficulty arose from the temperature being - 35 , 

 and the instrument in consequence difficult to handle. 

 But that a spectrum similar to the one at Oratunturi and 

 the one of 1871 on the Luosmavaara would have been 

 received I have not the slightest doubt. 



The galvanic measurements were effected as follows : — 

 First, the galvanometer was connected with the inner coil 

 of the " utstromnings " apparatus, 80 square metres in 

 area, when deflexion was observed ; secondly, it was 

 connected with the outer coil, 320 square metres in area ; 

 and thirdly, with both apparatuses combined, or 400 

 square metres in area. 



The deflexions were, in consequence of the small sensi- 

 tiveness of the galvanometer, weak ; but it was clearly 

 noticed that the current increased with the area of the 

 apparatus. As the deflexions varied considerably, it was 

 impossible to ascertain exactly their natural law, but it. 

 seemed apparent that the strength of the current was pro- 

 portionate to the surface area of the apparatus laid out. 

 The galvanometer used in this case was similar to the 

 other, but not so sensitive. If I designate the inclina- 

 tions at Oratunturi with O and those of Pietarintunturi 

 with P, the relative proportion of the sensitiveness of the 

 galvanometers would be 



P = 0-370, 



with very nearly the resistance of 20 Siemens units. The 

 metre was here divided into l'"2. The following shows 

 the results of the experiments : — 



December 29, 1882. — With the inner coil, or an area of 

 80 square metres : — 



First deflexion, 2'i parts of the metre. 



Second „ 09 ,, ,, 



Third ,, 10 ,, ,, 



Fourth ,, 2'4 ,, ,, 



Fifth „ 20 ,, ,, 



The temperature was on that day, as almost during the 

 whole period of experimenting here, —30°, or under. The 

 air was clear. 



December 31, 1882. — With the whole surface of the 

 apparatus, or an area of 400 square metres — 



First deflexion, I '6 parts of the metre. 



Second ,, 2"8 ,, ,, 



Third „ 3-8 „ ,, 



Fourth ,, 3 - i ,, „ 



Fifth „ 3-1 



With a Leclanchd's element the result was : — 



1. With the carbon pole against the mountain deflexion = -o - 2 

 With the zinc „ ,, ,, +7'5 

 Of which deflexion by the current from the atmosphere = 3-65 

 And ,, ,, ,, Leclanche's element =385 



2. With the carbon pole against the mountain deflexion = - i'5 

 With the zinc ,, ,, ,, =11*9 

 Of which deflexion by the current from the atmosphere =5 '2 

 And ,, „ ,, Leclanche's element =67 



The experiments with the different parts of the appa- 

 ratus resulted as follows : — 



I. Plane of equilibrium (o) 271 '61 



(b) 271-4/ : 

 Inner apparatus A = So square metres. 



271-5 open circuit. 



/in J- = 271 6 closed circuit. 



(*) 271 7 J 



Plane of equilibrium (c) = 270-4 open circuit. 



Deflexion from A = o"6. 



Outer apparatus B = 320 squire metre;. 



(a) Plane of equilibrium = 270-4 open circuit. 



(Jj ;: ;: gi*}=»yi-s «*-•*««««*. 



(b) ,, ,, = 2701 closed circuit. 

 Deflexion from B = 12. 



Entire apparatus C = 400 square metres. 



(a) Plane of equilibrium = 270-1 open circuit. 



j# " " *l°'% \ = 270-8 closed circuit. 



(*) .. .» 270 7 J 



(b) „ ,, = 269-7 open circuit. 

 Deflexion for C = 0-9. 



During these experiments it was noticed that the first 

 deflexion was always far greater than the subsequent 

 double, constant ones, and I have therefore noted this 

 one only. When the circuit was closed it was observed 

 that the needle pair always was at rest in the plane of 

 equilibrium. 



2. A. riane of equilibrium 269-7 open circuit. 



(a') ,, ,, 270-8 cloied circuit, 1st defl. 277-0 

 (b) ,, ,, 269S open circuit. 

 Deflexion for A = i - o 1st defl. =7'2 



B. (a) Plane of equilibrium 269 'S open circuit. 



(a) ,, „ 271 -3 cl ised circuit, 1st defl 281 - o 



(b) ,, ,, 270-4 open circuit. 



Deflexion fir B = 1 -2 Ist defl. = irS 



C. (a) Plane of equilibrium 270-4 open circuit. 



(a') ,, ,, 2718 closed circuit, 1st defl. 284-9 

 (/') ,, ,, 270-4 open circuit. 

 Deflexion for C = l'4 1st defl. = 14-5. 



3. A. (n) Plane ofequilibrium270-4 open circuit. 



( 1 ) ,, ,, 271-7 closed circuit, 1st defl. 278-2 

 lb) ,, ,, 270-8 open circuit. 

 Deflexion for A = i'i 1st defl. = 7 - 6 



B. (<?) Plane of equilibrium 27C8 open circuit. 



(a') ,, ,, 274-0 closed circuit, 1st defl. 282-0 

 (//) ,, ,, 273-6 open circuit. 

 Deflexion for B = 1 -8 1st defl. = 10S 



C. (a) Plane of equilibrium 274-5 open circuit. 



((/) ,, ,, 279-0 closed circuit, 1st defl. 292-3 

 (*) ,, ,, 275-6 open circuit. 

 Deflexion for C = 39 1st defl. = 17-2 



If these observations are connected we obtain : — 



A = 80 square metres 



B = 320 



C = 400 ,, 



Deflexion ist. defl. Deflexion. ist defl. 



1. ... o - 6 ... — ... I"2 ... — 



2. ... ro ... 72 ... i-2 ... 11S 



3. ... i"l ... 76 ... i-S ... 10S 



Deflexion. ist defl. 

 .. 09 ... — 



.. I'4 ■•• I4-5 

 .. 3-9 ... 172 



If it now be considered that the current from the atmo- 

 sphere was very variable, besides that the insulation was 

 rather imperfect, the results of these experiments are not 

 so reliable as might be desired. Still, this inference can 

 safely be drawn from them, that the strength of the current 

 increases with the area of the " utstromnings " apparatus 

 or with the number of points, but the natural law of the 

 increase I have not yet been able to determine. As will 

 be seen from the subjoined figures the conductive power 

 of the wire was that day very small, although the temper- 

 ature was comparatively high, viz. at 1 a.m. - 18° C, but 

 falling. 



The entire apparatus (C) with one of Leclanche's 

 elements : — 



(a) Plane of equilibrium 273-1 open circuit. 



(</) ,, ,, 275-3 the zinc pole against the mountain. 



(b) ,, „ 270'4carbon ,, „ 

 (/' ) ,, ,, 270-1 closed circuit. 



From this we obtain : the current from the atmosphere 

 = 1-5, and from the element = 2-45, which figures show 



