282 Mr. Whalton on a Safety Hood and Mouth-piece. [Ap ri l, 



lowest stratum of the apartment, where it is always the least 

 impure, to filtrate and cool it by transmission through the breath- 

 ing funnel, and thus to deprive it of the smoke and charcoal, 

 given off by the combustion, with which it is strongly impreg- 

 nated. 



No. 1, Roberts's invention as given by himself. 



No. 2, The same, with the suggested improvements. 



For these purposes the principle of Roberts's instrument is 

 well adapted, and its construction well imagined and invented ; 

 but several important improvements might be made which 

 would go far towards the completion of the machine, and which 

 immediately suggest themselves on a bare examination, or on 

 its application to experiment. 



The first alteraUon I would recommend is the insertion of a 

 screw joint into the upper part of the tube, at about two or three 

 inches from its origin, furnished with a washer of leather, and 

 made air-tight. This simple addition would secure two import- 

 ant advantages : first, it would enable the person using the hood 

 to relieve himself from exhaustion and oppression on coming 

 out of the apartment, by the instant admission and respiration of 

 pure atmospheric air, without incurring loss of time by removing 

 the whole hood, as is the case on its present construction ; and 



