j84 Mr Henry Meikle's Remarks and Experiments 



so many errors, that no confidence can be put in it. Mr Dal- 

 ton, to whom this department of science owes so much, has 

 made many experiments in this way to ascertain the force of 

 aqueous vapour at the freezing point ; and these seem to have 

 been very inconsistent, as Mr Dalton only concludes from them, 

 that this force is not greater than three, nor less than two tenths 

 of an inch of mercury.* The latter is Dr lire's estimate ; and 

 Mr Southern makes it 0.16 inch. At lower temperatures, I 

 suspect our tables are little else than a guess. 



But it is not less remarkable, that as great a diversity of opi- 

 nion should exist regarding the density of steam at the boiling 

 point, or still higher temperatures. Thus M. Gay Lussac 

 makes it to that of air, of the same temperature and pressure, as 

 5 to 8. Sir Humphrey Davy again alleges, that steam just 

 occupies the same volume as a mixture of its constituent gases 

 does under like circumstances. Its specific gravity would 

 thus be to that of air as 5 to 12, if not rather lower +. 



I shall now proceed to give an account of some experiments 

 of a different sort from those just mentioned, but connected with 

 this subject ; and which I should be glad to find carefully repeat- 

 ed by others. In order to determine how far the depression of 

 a wet thermometer inclosed with some drying substance, is affect- 

 ed by the capacity of the vessel, I made the following experi- 

 ments. Into a wide mouthed bottle capable of holding an im- 

 perial gallon, I put a quantity of sulphuric acid sufficient to cover 

 its bottom to a small depth ; and from the middle of the cork 

 I suspended two thermometers mounted upon one broad scale. 

 Their balls were about an inch separate, and on the same level ; 

 the one was covered with wet linen, and the other naked. At 

 the time of putting in the acid, the whole interior surface of the 

 bottle had been wetted with it ; and after the moist thermome- 

 ter became considerably depressed, I wetted the interior surface 

 afresh with acid, and then moved the bottle gently, so as to agi- 

 tate the thermometers considerably. This I had also done 

 from the beginning. After fully half an hour, the dry thermo- 



* Manchester Memoirs, Second Series, iii. 473. 



f Annales de Chimie, Ixxx. 218; Supp. Encyc. Britan. Art. Steam Engine, 

 p, 535. 



