326 Mr. Lubbock on Cask-Gaging. 



escaping into an atmosphere of another gas, and escaping into 

 one of its own kind. For this reason, Leslie's experiment 

 cited in the notes of his Treatise on Heat, and Mr. Faraday's 

 on the Escape of Gases through Capillary Tubes, (Quarterly 

 Journal of Science, vol. iii.) present results differing from 

 each other, from Mr. Graham's, and from the deductions of 

 theory. It is, 1 think, not improbable that when gases are 

 subjected to pass rapidly through a porous medium, as is the 

 case when they escape into a vacuum, instead of being re- 

 tarded by the opposing atmosphere of another gas, the angu- 

 lar irregularities of the channels of communication may pre- 

 sent greater obstruction to those gases which are disposed to 

 move with great velocity, than to those whose motion is not 

 so rapid. When, on the other hand, the gases mutually dif- 

 fuse into and retard each other, it becomes a question of time 

 and not of velocity; and the supposed inequality of obstruc- 

 tion may greatly diminish if not entirely disappear. 



This supposition has at least the advantage of reconciling, 

 in some degree, Mr. Graham's experiments with the theoreti- 

 cal deductions. But it is to be hoped that future researches 

 may throw further light on this interesting question. 



Primrose, near Clitheroe, April 12, 1834. 



LV. On Cask-Gaging. By J. W. Lubbock, Esq., V.P. and 

 Treas. U.S.* 



~|Z* EPLER was the first who endeavoured to reduce the art 

 of gaging to accurate principles, in his work entitled, 

 Nova Stereomeiria Doliorum Vinariorwn, published in 1615. 

 He gave in this work the solution of several new problems re- 

 lative to the content of various solids, and he showed how 

 the solution of others might be made to rest upon considera- 

 tions more simple than those which had previously been em- 

 ployed. The art of gaging is one of such practical import- 

 ance in all countries, but more especially in our own, in con- 

 sequence of the immense duties annually levied by the Go- 

 vernment upon various liquids, the quantity of which is ascer- 

 tained by gaging separately the casks in which they are con- 

 tained f, that I trust the following remarks will not be consi- 

 dered superfluous, although it is not in my power at the pre- 

 sent time to do more than to show how the elementary prin- 

 ciples of the mensuration of solids should be applied to the 



* Communicated by the Author. 



■f The number of casks gaged annually on the (mays in this port alone, 

 before they arc deposited in store, amounts to more than 100,000. The 

 duty on brandy is 2"2s. (j<t. per gallon. 



