64 REPORT— 1839. 



terminating orifice of either of the cocks, so as to fill the space between 

 its extremity and the plug, and retain this liquid by the end of the 

 fore-finger. Insert the extremity thus prepared into the vessel that 

 contains the preferred reagent, and remove the finger. Turn the plug 

 of the inserted stop-cock for the admission of the reagent. Apply the 

 lips, or an exhausting syringe, to the orifice of the upper cock, and 

 commence the process of exhaustion. Gently turn the plug of this 

 upper cock during the exhausting process, and when the reagent has 

 risen so as to occupy 30, 40, or more of the lower divisions of the tube, 

 turn back the plug, and close the upper stop-cock. After a moment's 

 pause, close the lower stop-cock also. Note the number of divisions 

 unoccupied by the reagent, the tube being held upright. 



Apply the finger to the lower orifice of the cock which has been 

 immersed, in order to retain that portion of the reagent which will 

 occupy the space below the plug. Agitate the tube with its contents. 

 Immerse the same end of the tube again in the vessel containing the 

 reagent, and remove the finger. Turn the plug of the lower cock, and 

 watch the rise of the liquid within the tube until it has attained its 

 fixed level. Then close the stop-cock, by turning back the plug, and 

 replace the finger. Agitate well. 



Repeat this simple process until the reagent ceases to absorb air 

 from within the tube. Then suspend the tube by a loop of wire from 

 a pin or nail fixed into some convenient corner of the wall, until the 

 interior surface has become drained, and a permanent level established. 

 Now open the upper cock, when a small quantity of air will rush into 

 the tube to relieve the tension, and with it, generally, a single drop of 

 the reagent that had occupied the small space within the bore of the 

 upper cock beneath its plug. 



The difference between the number of divisions, or parts, first ob- 

 served to be unoccupied by the reagent, and the number of parts lastly 

 observed to be unoccupied, will be the number of parts of carbonic 

 acid gas that was contained in the number of parts of air first observed. 



It will be evident that a correction for tension will be necessary to 

 complete the process. This can be easily obtained ; and a table once 

 supplied, and entered in the laboratory note-book, will suffice for all 

 experiments with this instrument. 



Mr. Coathupe explained a process by which the operator may con- 

 struct such a table for himself. 



On a New Safety Lamp. By the Baron Eugene de Menil. 



The peculiarity of this lamp consists in its open chimney, the prin- 

 ciple of small apertures being employed only for the admission of air, 

 on each side of the wick, through tubes capped by metallic gauze. The 

 strong flint glass cylinder inclosing the flame is protected by a dozen 

 small bars of tinned iron. The oil is kept in the lamp at a constant 

 level. The chimney, which rises above the general body of the lamp, 

 is contracted at the summit and covered (not closely) by an arched 



