922 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



great success of the apparatus, becoming rare and dear, Mr. Gali- 

 bert was obliged to have recourse to cylinders of artificial tissue, 

 perfectly impermea1)le and very strong, which he prepares by 

 glueing together two strong linen and hemp cloths, each coated 

 with eight layers of India rubber varnish. They are filled in a 

 few seconds by means of a small bellows, and are capable of con- 

 taining eighty litres (nearly 141 pints) of air. They are carried 

 on the back of the operator like a knapsack, by means of straps. 

 The communication between the air of the reservoir and the mouth 

 and respiratory organs is made by two fixed tubes of India rubber, 

 that of aspiration at the bottom of the reservoir, and that of expira- 

 tion at the top of the bag, l)oth tubes terminating in a sort of 

 mouth-piece, which the operator places between his teeth. A 

 strong clip prevents breathing by the nostrils, and the eyes are 

 protected b}^ two concave glasses set in a circular band of leather, 

 which surrounds the head and shuts hermetically. Thus pro- 

 vided with air, the operator can penetrate and remtdn without 

 suffering in the most mephytic and foul atmospheres. If his 

 sojourn should be prolonged he can carry with him several cylin- 

 ders for exchange, ready filled. He carries, also, suspended at his 

 waist, an India rubber hollow ball or tube, which sounds on the 

 hand being pressed against it, in case of danger. This apparatus 

 has been adopted by the fire brigade of Paris and of many depart- 

 ments, by the general gas company, the navy, &c. It is absolutely 

 indispensible for well-sinkers, sewerage workmen, repairers of gas- 

 mains, and those who penetrate places in distilleries where fer- 

 mentation is going on, as well as those in laboratories when nox- 

 ious gases are generated. 



Corrugated Iron. 



Mr. Richard Montgomery exhibited several specimens of his cor- 

 rugated iron. He compared the strength of ordinary sheets of 

 iron with those of the same thickness which had been corrugated, 

 and showed that the lateral resistance was greatly increassd by the 

 process of corrugation. 



Mr. Norman AViard said a boiler made of this corrugated iron 

 would be so stiff that it could not make one trip from here to 

 Albany. It is the elasticity of boilers, like those of the St. John, 

 that renders it possible for them to sustain the pressure they are 

 suliject to. By corrugating the boiler plates, they are made fifty 

 times as stiff as the plain boiler. It is well known that metals 



