1 4 Mr. J. JefFreys's Expeinments o?i Exosmose "with reference 



the water and to the gas, the density was still sufficient to de- 

 tain the water during the time the gas kept extricating itself, 

 and constantly occupying the pores of the ware to the exclu- 

 sion from them of the water. Though the chief force, the 

 mechanical one, acted upon both fluids, a little might turn 

 the scale in favour of the relief taking place by a departure of 

 the one and not of the other. Now quite enough to decide 

 the point in favour of the exit of the gas might be found in 

 the well-established diffusive tendency of gases shown in the 

 phffinomena of electric exosmose, by which the gas on the 

 one hand would seek a departure into the atmosphere through 

 the ware, while on the other hand the cohesion of the liquid 

 particles would favour their remaining together within it. 

 This process went on until the gas was nearly all discharged, 

 the small remaining quantity being detained by the affinity 

 of the alkali and the water. 



In the instance of great porosity first noticed, the results 

 explain themselves at once. Here there was not closeness of 

 texture sufficient for even such a detention of the contents as 

 would enable the gas and liquid to part, and the process of 

 exosmose to remove the former ; but both fluids were pro- 

 pelled through the pores, the water in fine rain which formed 

 into a mist. 



Atmospheric air was not tried with water, on account of 

 the difficulty of retaining it condensed into water while the 

 vessel is being secured ; though with apparatus devised for 

 the purpose the experiment might easily be made, if ware 

 of the peculiar closeness were procurable. The impregnation 

 of water with hydro-sulphurous acid gas, which was being con- 

 ducted on a large scale at the time, would have enabled me 

 to try it, had the machinery constructed for that purpose 

 been capable of exercising a pressure of more than two at- 

 mospheres, which was not sufficient for the effect. 



Of the compositions of which the various kinds of stone- 

 ware and china are manufactured in England, there are pro- 

 bably some which by a certain heat would be brought to the 

 points of densit}' suited for the experiments. Specimens of 

 Staffordshire earthen and China ware, however, (all of which 

 are absorbent,) upon being treated with greater heat than those 

 at which they had been manufactured, did not pass into any 

 state of great density, but after a certain approximation of 

 their parts, a decomposition of them commenced, attended 

 with a swelling or enlargement of the whole, and an increase 

 of porosity. I also doubt if the body used for the Derby 

 porcelain would pass at any heat into the suitable texture; 

 and from experiments made on oriental china from Canton, 



