166 Proceedings of the Royal Irish Academy. 



The alumina includes a trace of phosphate and some titanium dioxide. 



This result fully confii-ms Mi\ Seymour's opinion, if we assume that most 

 of the iron originally present as ferrous oxide has been oxidized, and that the 

 lime has been almost completely removed, and in part replaced by magnesia 

 — changes which would natiu-ally result in the process of weathering. The 

 weathering must have taken place when the rock was exposed to atmospheric 

 influences, and mainly through the action of water. It cannot be supposed 

 that the rock from which the vessel was fashioned contained the reatlily 

 soluble salts which 1 detected in it ; the presence of these salts also 

 precludes the idea that any appi-eciable weathering has taken place since the 

 vessel was used as a lamp. It is highly probable that the weathered rock was 

 selected on account of the ease with wliich it could be cut into the required 

 form. How is the saline matter to be accoimted for ? There cannot, 1 

 think, be any reasonable doubt that the sodium chloride has its origin in the 

 use of ordinary domestic grease, obtained in the process of cooking, as a 

 material for buruiug. Such grease, unless it were carefidly purified, would 

 be certain to coutaiu nitrogenous matter ; and this, if bvuut, woidd accoimt for 

 the ammonium compounds also pi-esent. 



The saline matter was almost completely free from potash. The quantity 

 of potash was so small that it was ouly detected with difficulty by means of 

 the spectroscope. Tliis almost complete aljsence of potash is difficult to 

 explain. Some kind of wick must have been used, probably a vegetable 

 substance, and its ash would certainly contain potash. Moreover, potash is 

 usually found in animal tissue, such as would have given rise to the 

 ammonium compounils found The only explanation I can offer is that any 

 potash derived from the substances burnt in the lamp formed insoluble 

 compoimds with constituents of the rock. That potash may replace lime in 

 certain silicates is well known, and perhaps this is the reason why lime, which 

 enters so little into the comi>osition of the rock, is present in notable quantity 

 in the saline matter. 



What is the explanation of the large proix)rtion of sulphates in the saline 

 matter? For the reason alreaily refen-etl to, soluble sulphates could scarcely 

 have been present in the original weathered rock. The small quantity of 

 sulphur in the organic substances, likely to have been associated with the 

 grease burnt, would not account for the sulphates found. In hair, which is 

 rich in sulphiu: in comparison with animal tissues, the ratio of sidphur to 

 nitrogen is 1 to 3"4 ; whereas, in the saline matter removed from the lamp, the 

 corresponding ratio is 1 to 004. A certain amount of sulphates must have 

 been contained in the common salt associated with the grease burnt ; but only 

 a small psat of the sulphur can be accounted for in this way. It is obvious 



