82 



Laboratory Arts 



of 120 apart, mounted upon a ground conical pillar, which 

 may be tilted through a quadrant and clamped by a milled 

 screw. There is also a bye-pass which enables the jets to be 

 changed instantly by swinging round without the extinction of 

 the flame. By this means all the above-mentioned flames are 

 available. No better tool could be desired, though the bye- 

 pass might be a little stronger mechanically. 



Messrs. Fletcher, Russell & Co.'s blowpipe, after being cut 

 down, will be found an exceptionally handy tool, as one tap 

 controls both gas and air, and ensures a perfect proportion of 



FIG. 71. Fletcher, Russell & Co.'s new pattern C 10 B blowpipe. 



gas and air at all jet apertures. The actual jet is constant for 

 all flames, and an advancing sleeve over the outer tube enables 

 one to get rid of the white tip for various flames. The actual 

 working of this for small jets is more easy than that of Letcher's 

 machine, as the flame comes gradually and with great precision 

 to the size required, while in Letcher's, the small flame is only 

 obtained by moving the jet round beyond the correct central 

 position, as though there were too large an air supply. 



The actual regulation of the gas and air supply requires to 

 be made for each kind of gas used; a blowpipe correctly 

 adjusted in one town does not necessarily work well in 

 another, owing to the difference in the composition of the gas. 



