ANNIVERSARY ADDRESS OF THE PRESIDENT. XXVU 



I need scarcely remind you that the manner in which iron pyrites 

 is formed mider certain conditions, when organic matter is present, is 

 now well understood. Perhaps one of the most illustrative cases is 

 that of the formation of iron pyrites from the decomposition of the 

 bodies of mice in a solution of sulphate of iron, described by Mr. 

 Pepys, in 1811, in the first series of our Transactions, vol. i. There 

 is also an instance of a dog having fallen down a mine-shaft near 

 Mousehole, Cornwall, at the bottom of which there appears to have 

 been a solution of sulphate of iron. Its remains, when disco- 

 vered some time afterwards, were found surrounded by sulphuret of 

 iron. In such cases, the hydrogen evolved from the decomposition 

 of the animal matter would appear to take the oxygen both from the 

 sulphuric acid and oxide of iron, so that iron pyrites, or bisulphuret 

 of iron, is produced. Artificial iron pyrites has also been formed 

 in the dry way. The ammoniacal liquor of gas-works contains much 

 sulphuretted hydrogen. An instance is known where, in employing 

 this liquid in the manufacture of sal ammoniac, the sulphur of the 

 sulphuretted hydrogen combined with the iron of the vessel in which 

 the operation was conducted, and formed crystallized iron pyrites of 

 a bright yellow colour, which have retained their lustre during many 

 years to the present time. 



In a note on the Souffriere of St. Vincent, Major Henry Davis 

 calls attention to the evidence of eruptions prior to that of 1812, 

 when such an abundance of ashes was vomited forth from this vol- 

 cano and scattered to great distances. He found beds of vegetable 

 matter interstratified with volcanic layers, marking times of repose 

 when parts, at least, of the mountain could be clothed by plants ; and 

 he observes, that in some instances we may conclude, from the thick- 

 ness of the vegetable beds, long intervals of time to have elapsed 

 between the eruptions. The manner in which a succession of vol- 

 canic eruptions may be thus geologically chronicled is not only inter- 

 esting in itself, but such facts as Major Davis notices are valuable 

 as illustrating the mode in which, during the long lapse of geological 

 time since ashes were ejected from volcanic vents (and we have rea- 

 son to conclude that such were driven out from various parts of the 

 earth's surface at very early periods), not only may vegetable matter 

 have been imbedded amid ashes, but the remains of animal life also. 

 Certainly the chances of preserving these remains when the move- 

 ments on the earth's crust were such as to depress volcanic districts 

 beneath the sea are but small. We have only to consider the effects 

 which would be produced by sinking any modern volcanic region, 

 such as Etna or Vesuvius, or any district of extinct volcanos, such as 

 Central France, beneath the sea, to judge of the slight chance of 

 preser\ing such alternations of vegetable matter and volcanic ashes 

 and cinders from removal by the breakers as they slowly worked 

 upon the slightly coherent materials. Supposing a gradual descent 

 of the land, so that finally the whole volcanic region would be sub- 

 merged, we should scarcely expect any of the loose materials to re- 

 main as accumulated in the atmosphere, but to be spread about be- 

 neath the water by tidal streams, or ocean and sea currents. Under 



