On the Peltier Effect at different Temperatures. 359 



The system of currents indicated by these numbers is that 

 approximately shown by the equations given above, the phase, 

 however, being different. * Along the meridian, on which the 

 local time is 4, the currents now from the equator towards the 

 north, they turn round in our latitude towards east and west, 

 join on either side again to go south, where the local time is 

 half-past 7 in the morning, and come back along the equator. 



The numbers given in the columns as intensity become 

 amperes when multiplied by 10~ 6 . They are approximately 

 of the same magnitude as the currents we are accustomed to 

 send through our vacuum-tubes ; but as the thickness of layer 

 through which they are distributed must be very large com- 

 pared to that on which we experiment, the current-intensity 

 at such place is very small, far too small to cause luminosity. 

 The currents, on the whole, are weaker at Greenwich than at 

 Bombay ; but while they almost vanish at one time at Bom- 

 bay, making the ratio of the strongest to the weakest current 

 equal to 73, that ratio is only 3J at Greenwich. The minimum 

 at Greenwich in the early morning is as pronounced at the 

 afternoon minimum, but much less so at Bombay. 



On the whole the numbers, both as regards direction and 

 intensity, show such a remarkable regularity that there is 

 good hope of obtaining a good mathematical representation of 

 their distribution. 



But more detailed investigations will require much time 

 and consideration. They can hardly upset the conclusion 

 arrived at in this paper, that the greater part of the diurnal 

 variation is due to disturbing causes outside the earth's sur- 

 face. I forbear at present from entering into some very 

 curious conclusions to which we seem almost forced if we 

 adopt this view. 



It will be interesting to apply the method here used to the 

 other periodic variations of terrestrial magnetism which have 

 been discovered. 



XL VIII. On the Peltier Effect at different Temperatures* . • 

 By G. Gore, LL.D., F.R.S.f 



IN order to examine this question I made the following- 

 experiments : — A current of about *10 ampere was 

 passed, during five minutes, through a thermoelectric pile, 



* See Campbell, Proc. Roy. Soc. Edin. vol. xi. 1882-83, p. 807, and 

 vol. xii. 1883-84, p. 293 ; consult also a paper by Naccari and Bellati on 

 the same subject, Wiedemann's Beibldtter, 1878, vol. ii. p. 223 ; and one 

 by Bellati, ibid. vol. iii. p. 638. 



f Communicated by tlie Author, having been read before the Birming- 

 ham Philosophical Society, February 11, 1886. 



