474- 



When the bulb of a thermometer, wrapped in fine lint, has been 

 dipped in the sulphureous liquor, if it be simply exposed to the air it 

 sinks to about zero of Fahrenheit's scale, although by a similar eva- 

 poration of ether the cold produced is not below 20. 



If a thermometer, coated as before, and wetted with the sulphuret, 

 be placed in the receiver of an air-pump, a cold of 65 or 70 below 

 is easily obtained, by a vacuum which supports one fourth of an 

 inch of mercury ; and if the air-pump can exhaust as far as one eighth 

 of an inch, the thermometer sinks to 81 or 82 in less than two 

 minutes, even though the thermometer at the commencement of the 

 experiment was as high as 70 above 0. 



Hence the freezing of mercury is an experiment that may be per- 

 formed at any time, and with no more apparatus than a common air- 

 pump, and enough of the sulphuret to moisten the bulb of a thermo- 

 meter. Since sulphuric acid has no affinity for the sulphuret, it has 

 no effect in adding to the degree of cold produced upon the principle 

 upon which that is employed by Mr. Leslie, excepting in so far as 

 it removes any moisture that may be present in the air, and which 

 in some measure impedes the process until it is converted into a 

 hoar frost, that may be seen adherent to the bulb of the thermo- 

 meter. 



On a saline Substance from Mount Vesuvius. By James Smithson, 

 Esq. F.R.S. Read July 8, 1813. [Phil. Trans. 1813, p. 256.] 



From the strong evidence we have that a very large proportion of 

 the world, as we now see it, has at some period been either in a state 

 of actual combustion, or has felt the effects of heat, a high interest, 

 says the author, attaches itself to volcanoes and their ejections, as 

 partial instances of similar operations now going on. 



In support of the igneous origin of primitive strata, it is observed, 

 not only that no crystal imbedded in them contains water, but that 

 none of the materials of the strata contain water in any state. 



The subject of the present experiments was thrown out in a liquid 

 state from the cone of Vesuvius about the year 1792 or 1793. 



It was of a dirty white colour, with streaks of yellow and green. 



When heated, it fused without any loss of weight. When fused 

 on charcoal, it was converted into sulphuret of potash. 



In water it dissolved readily, leaving particles of specular iron and 

 oxide of copper. Muriate of platina caused a copious precipitate 

 from the solution, from the presence of potash. Nitrate of barytes 

 afforded an abundant precipitate of sulphate of barytes. 



Sulphate of silver gave a curd-like precipitate, showing the pre- 

 sence of muriatic acid. 



Prussiate of soda gave a red precipitate, consisting of pru&siate of 

 copper. Carbonate, or oxalate of soda or potash, occasioned no pre- 

 cipitation of any kind of earth ; nor did any means employed detect 

 the presence of boracic, or of any other acid, excepting the sulphuric 

 and muriatic. 



