fof collecting and transferring Gases, f 45 



V/Ub the utility of the instrumems before named, to render 

 any further observations concerning them necessary. 



,4t is in consequence of such reflections, and the invita- 

 tions I have received from others, whose judgement I re- 

 spect, that I take the freedom to lay before the public the 

 annexed sketch of a pneumatic table, which in the routine 

 ot niy profession I have found extremely useful in operating 

 on ^ases, which I flatter myself will be found aaacquisitioa 

 among the apparatus to the laboratoty. 



Tlie discovery of the gases, and their great importance In 

 the researches of modern chemistry, have occasioned, as is 

 well known, the necessity of some peculiar instruments, by 

 means of which these bodies may be caught, collected, 

 transferred, and. submitted to the action of other bodies, 

 Aniong these _the very simple aad ingenious reservoir, in- 

 vented by Dr. Priestley, and named by him the pneumatic 

 trough, is the most intlispensable. Several alterations have 

 been proposed in the structure of this vessel, to reader it 

 more. convenient for use ; but these, it may be said, relate 

 either to its form only, or to its !\eatness and general ap- 

 pearance, and not to its principles, or application and utility,^ 

 as connected with the operations of pneumatic chemistry. 

 Fig. I. (Plate VII.) represents a wooden table three feet 

 six inches high, two feet ten inches long, and one toot 

 eight inches broad. At each end of this table, and at a 

 depth of ten inches from its upper edge, is a moveable 

 board or platform d d measuring 18 inches by IC^. These 

 platforms are supported horizontally by swing-brackets 

 e e, which may be turned aside to allow the platforms d d 

 to fall down between the inner sides of the legs of the 

 table. The brackets e e are then concealed from view. The 

 platforms d d serve to support table furnaces, retorts, and 

 stands,, or other apparatus employed in the production of 

 gases. Fia:. 2. is i^w ceconomical lamp furnace with its 

 retort in action, to show the use of the platforms. The 

 upper part of the pneumatic table is siuTounded by a broad 

 rim or border xx two inches and a half deep, ^o as to 

 form a shallow tray. It is of rather larger dimensions 

 than the table, projecting over the frame of it about 

 three fourths of an u^h. This tray (as 1 shall call it) is 

 divided into two unequal compartments, namely, a cistern 

 a a occupying one end or side, and a stage or shallow plain 

 b occupy mg the other. The cistern a a is 16 inches deep, 

 J 9 wide, and 16 broad ; the stage or plain b occupies the 

 l'em;iining part of the tray b. When the table is intended to 



be 



