186 FRAGMENTS OF SCIENCE. 



judice to the action. A wire-gauze cover, shown in 

 plan under fig. 5, keeps the substances from falling out 

 of the respirator. A layer of caustic lime may be 

 added for the absorption of carbonic acid ; but in the 

 densest smoke that we have hitherto employed, it has 

 not been found necessary, nor is it shown in the figure. 

 In a flaming building, indeed, the mixture of air with 

 the smoke never permits the carbonic acid to become 

 so dense as to be irrespirable ; but in a place where the 

 gas is present in undue quantity, the fragments of lime 

 would materially mitigate its action. 



In a small cellar-like chamber with a stone flooring 

 and stone walls, the first experiments were made. We 

 placed there furnaces containing resinous pine-wood, 

 lighted the wood, and, placing over it a lid which 

 prevented too brisk a circulation of the air, generated 

 dense volumes of smoke. With our eyes protected by 

 suitable glasses, my assistant and I have remained for 

 half an hour and more in smoke so dense and pungent 

 that a single inhalation, through the undefended mouth, 

 would be perfectly unendurable. We might have pro- 

 longed our stay for hours. Having thus far perfected 

 the instrument, I wrote to the chief officer of the 

 Metropolitan Fire Brigade, asking him whether such 

 a respirator would be of use to him. His reply was 

 prompt ; it would be most valuable. He had, however, 

 made himself acquainted with every contrivance of the 

 kind in this and other countries, and had found none 

 of them of any practical use. He offered to come and 

 test it here, or to place a room at my disposal in the 

 City. At my request he came here, accompanied by 

 three of his men. Our small room was filled with 

 smoke to their entire satisfaction. The three men 

 went successively into it, and remained there as long 

 as Captain Shaw wished them. On coming out they 



