56 



to the vapour of these substances. For this purpose bis- 

 muth and palladium at a moderate heat, and gold at a high 

 temperature, afforded distinguishing tests. To determine 

 the relative attraction of fluorine for those metals upon 

 which it does not act except at high temperatures, they used 

 as positive poles of a battery of sixty pair of plates, mois- 

 tened fluoride of lead, palladium, platinum, gold, and rho- 

 dium. The palladium and platinum were always acted 

 upon, the gold occasionally, and the rhodium never ; from 

 which they suppose that fluorine might be obtained in an 

 insulated state, by electrolyzing fluoride of lead in a tube of 

 fluor spar, using rhodium as the positive pole. 



They were unable to repeat M. Baudrimont's experi- 

 ments in glass or fluor spar vessels. Supposing that the gas 

 he obtained was an oxide of fluorine, they heated in a dry 

 glass tube iodic acid and fluoride of mercury ; supposing 

 that since iodine decomposes fluoride of mercury, the oxygen 

 and fluorine, being set free from their combinations with op- 

 positely electrical bodies (iodine and mercury), would be in 

 the most favourable condition for combining. On the appli- 

 cation of a moderate heat a pale yellow vapour rose in the 

 tube, which did not act on the glass, and bleached litmus. 



Mr. Mallet read a paper " On an hitherto unobserved 

 Structure discovered in certain Trap Rocks in the County of 

 Galway." 



The town of Galway is built upon a part of an immense 

 trap dyke, which extends under the sea and to a consider- 

 able distance up Lough Corrib. Large excavations for a 

 dock are now making in this rock at Galway, and afford 

 a convenient opportunity of examining its structure. It 

 separates the limestone on the east (which it tilts up) from 

 the sienite of Cunnemara on the west, (which it overlies or 

 mingles with.) 



