



APPLICATIONS OF CENTRIFUGAL FORCE. 



147 



rotation, the air within the radiating strips is compelled 

 to rotate with it, and is expelled by centrifugal force 

 through the tube as a powerful current, while a new 



FIG. 103 (an.proj. 3- real size). 



supply of air is conveyed into the interior from the 

 outside through the circular hole at the top. 



Similar contrivances are employed on a large scale 

 in various technical arts, for the purpose of producing 

 powerful currents of air, as in mining, smelting, etc. 



The radiating strips are cut from stout drawing paper, l cm wider 

 than their required height ; they are sharply folded l cm from the 

 edge, along their length, and the portions bent in are glued to the 

 i disc, radiating regularly from the centre ; after drying, every strip 

 which is not quite vertical is bent straight with the hand. The cap 

 should be made of rather thin cardboard ; fig. 104 represents a 

 model, on a sma.ll scale, for cutting the cardboard. In cutting it out 

 and putting it together the following points must be attended to : 

 1st, The circumference of the piece which forms the top of the cap is 

 314 times as great as its diameter, but the strip which forms the 

 cylinder must be taken about l cm longer than this, since the external 

 diameter of the cap is greater than the internal ; 2nd, The curved 



L 2 



