M. J.-M. Gaugain on Grove's Gas Battery. 465 



1845, April 15.— See Pbil. Mag. vol. xxx. p. 127. 

 1845, July 14. — On the top of -Scuirmorc, near Glenquoich. 



Meantime. Above horizon, 



h m o / 



5 24 Altitude of Arago's neutral point. b* 40 



R=232° max. polarization in zenith plane. 



1845, September 6. — Barom. 30*10 in. Fine clay; a milky 

 sky. 



110 R= 17° max. pol. in zenith plane. 



5 31 It =23°. Arago's neutral point . . 11 



5 41 Arago's secondary neut. point seen in hor. 13 24 



6 36 Arago's neutral point .. .. 19 10 



5 43 \ Babinet's. R= 28i° maximum polariza- \ 24 



6 28 J tion, 24° in horizon .. J 20 24 



1850, July 1, 15, 29.— See Phil. Mag. vol. xxx. p. 176. 

 1850, July 9. — Barom. 2979 in., rising. Fine clear sky. 



6 56 Bands just visible at the land horizon. 



7 5 Bands invisible close to land horizon. 



7 21 During the previous 21 minutes no trace of the + bands 

 was seen. At 7 h 21 ra they were seen, and became ra- 

 pidly brighter. 



The positive action which here produced the secondary neutral 

 point was not strong enough to produce it by exhibiting the + 

 bands counteracting the — ones at some height above the hori- 

 zon ; but it was strong enough to neutralize them for 21 minutes, 

 and to weaken them greatly when they did appear. 



LIX. On Grove's Gas Battery. By M. J.-M. Gaugain*. 



ALL physicists are acquainted with Mr. Grove's gas-ele- 

 ment, and with the theory of it which he has given. 

 This theory is now generally admitted ; and probably few persons 

 remember the objections which from time to time have been 

 urged against it, especially by M. Schonbein. I have been led 

 by other investigations to return to the subject ; and although 

 I was not acquainted beforehand with M. Schonbein's investi- 

 gation, I have arrived at almost the same conclusions. 



I used a mode of investigation quite different from those 

 hitherto employed. I only worked with one element at a time ; 

 and instead of measuring the intensity of the current, I mea- 

 sured the, electromotive force directly by the method of opposi- 

 tion. I could thus numerically estimate the influence of the 

 modifications which I have successively introduced into the 

 arrangement of the couple. 



Mr. Grove thinks it indispensable that each of the platinum 

 electrodes in his gas-couple should be simultaneously in contact 

 * Translated from the Comptes Rendus, February 25. 



Phil. Mag. S. 4. Vol. 33. No. 225. June 1867. 2 H 



