Scientific Lectures. 



215 



The Babcock Fire Extinguisher. 

 Carbonic acid has been made use of in extinguishing: combustion. 

 Here we have a Babcock fire extinguisher, a vessel containing bicarbo- 

 nate of soda dissolved in water ; this is a substance charged with car- 

 bonic acid. In the upper part of the apparatus is a cup of sulphuric 

 acid. By turning the handle we set free the sulphuric acid, which 

 acts upon the bicarbonate of soda, and the carbonic acid is evolved in 

 the form of gas, which cannot escape till we open this valve, when a 

 jet of carbonic acid and of water charged with sulphate of soda is 

 thrown upon the fire. It is not claimed that' this will take the place 

 of water for buildings already wrapped in flames ; but if we have it 

 always on hand, so that it is only necessary to touch a spring to put 

 it in operation, it enables us to put out the fire before it has done 

 any serious damage. A great many fires have been already pre- 

 vented by its use. 



Interior of the Fire Extinguisher. 



The construction of the fire extinguisher is shown in this diagram. 



The leaden bucket A, holds the charge of acid, and is kept in its 



upright position by the leaden stopper O, attached to the rod B, 



coming through cap C. To prepare the extinguisher for use requires 



