15S Proceedings of Philosophical Societies. [Auc. 



of iron, with some earthy matter. Mr. Smithson, hy way of 

 introduction to His paper, gives a view of his opinions about the 

 origin of the earth. In his opinion, it was originally a sun, or a 

 comet, and was brought to the state in which it is at present by 

 undergoing combustion at the surface. The volcanoes are the 

 relics of this original combustion, and the materials were the 

 metallic bases of the earthy substances of which the primitive 

 strata are composed. As a proof that these primitive strata have 

 been formed by combustion, he mentions that garnets, horn- 

 blende, and other crystals found in them, contain no water, and 

 that little or no water is to be found in the primitive strata them- 

 selves. 



3. Observations by Dr. Maicet on the cold produced by the 

 evaporation of sulphuret of carbon. This liquid evaporates more 

 rapidly than any other, and produces in consequence a greater 

 degree of cold. A spirit of wine thermometer, having its bulb 

 surrounded with cotton cloth or lint, if dipped into sulphuret 

 of carbon, and suspended in the air, sinks from 60° to 0. If it 

 be put into the receiver of an air-pump, and a moderate ex- 

 haustion be mace, it sinks from G0° to — Sl° (1 have seen 

 it myself in these circumstances sink from 7 i<? to ~~ 7-°)- 

 If a tube containing mercury be treated in the same way, the 

 mercury may be readily frozen, even in summer. The drier the 

 air in the receiver is, the more easily is the cold produced. Hence 

 the presence of sulphuric acid may be of some little service in 

 removing the vapour from the air in the receiver previous to 

 exhaustion ; otherwise it occasions no increase of the cold. 



4. Observations on the composition of fluor spar, and on its 

 acid basis, by HSir Humphry Davy. The author begins his paper 

 with an historical detail of the attempts made by himself, and 

 Gay-Lussac and Thenard, to decompose fluoric acid, and the 

 ill success of these attempts. It appears from the compounds 

 into which fluoric acid enters, that tbe weight of an integrant 

 particle of it does not exceed l - 05, supposing an atom of oxygen 

 to weigh 1 . Hence it follows that if it is a compound of oxygen 

 and an inflammable base, the base can only have the 20th part 

 of the weight of the oxygen. This supposition he considers as 

 unlikely to be correct. He therefore supposes that fluoric acid, 

 like muriatic acid, is a compound of hydrogen and an unknown 

 supporter of combustion, to which he gives the name of fluo- 

 rine. He relates many experiments made in order to obtain 

 fluorine in a separate state, but none of them were attended with 

 success. As chlorine has the property of decomposing several 

 oxides, and driving off their oxygen, it occurred to him as 

 likely that it might in certain cases drive oil* fluorine. Filiate of 

 silvei and f uate of mercury, with this view, were acted upon by 

 chlorine. The fluoric acid (or fluorine) was. disengaged, and 

 horn silver and corrosive sublimate formed ; but no fluorine was 



