BELLOWS. 65 



SCREENS. 



These are made of perforated caoutchouc drapery, or whale- 

 bone, which may, in many cases, be substituted in safes, 

 windows, and cupboards for metal gauzes, on account of its 

 cheapness, and not being liable to corrode. 



TUNNELS. 



Are made of cord ware, hollow ware, elastic compound, or 

 caoutchouc whalebone. They are designed for druggists' use, as a 

 substitute for glass or wedgewood. For common use, they pos- 

 sess the superiority over tin of not being liable to be damaged, or 

 to corrosion. When made of cord ware, hollow ware, or elastic 

 compound, they have another advantage, that of being portable. 

 See plate xiii., fig. 3. 



BELLOWS. 



Wooden bellows are covered with the vulcanized fabrics, as 

 proposed under the head of bellows' covering. An improved 

 kind of smith and other bellows is made by covering a hoop of 

 iron or wood, as represented in plate xiii., fig. 4, and afterwards 

 cementing the covering to the hoop. This kind is made up 

 only at the factories, while the gum is in a soft state. Beside 

 the advantages which have been claimed for these fabrics, under 

 the head of Bellows Covering, this article avoids entirely the 

 great objection of leakage, about the parts where leather is com- 

 monly nailed to the wood, of which almost every person must 

 have knowledge who has had much occasion to use bellows. 



