540 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



side expiratory valves nearly all the moisture of the breath 

 is set free. 18 A,Jtme 9, 1876, 326. 



ELECTRICAL ALARM AGAINST CARBONIC OXIDE. 



The following is the general construction of a small aj^pa- 

 ratus, designed by Ansell, which is said to indicate the pres- 

 ence of a comparatively small amount of carbonic oxide in 

 the atmosphere by starting an electrical alarm, and seems 

 to be especially adapted to sleeping-chambers, where there 

 may be any danger from the escape of gas. A pear-shaped 

 vessel, closed at the top with a porous membrane best with 

 an unglazed earthen plate is connected at the bottom with 

 two communicating tubes filled to a certain height with mer- 

 cury. The tube not immediately connected with the vessel 

 ends in a small hollow glass bulb, containing a platinum 

 w^ire reaching nearly to the mercury. The poles of a bat- 

 tery, including in its circuit an alarm-bell, are connected re- 

 spectively with this wdre and the mercury. In an atmos- 

 phere containing carbonic oxide, this gas, of lower specific 

 gravity, will difi"use so much more rapidly through the por- 

 ous membrane into the vessel filled w^ith air, that sufiicient 

 pressure will be produced to cause a depression of the mer- 

 cury in the tube connected with it, and a corresponding ele- 

 vation of it in the other, until it comes in contact with the 

 platinum ware, when the alarm wdll be sounded by the com- 

 pletion of the circuit. 18 C\ February 9, 1876, 81. 



