56 SCIENTIFIC AMUSEMENTS. 



three-legged stand of iron (fig. 7) and place a good sized Bunsen 

 gas-burner under the copper part so that the flame laps well 

 round it. Specially constructed gas-burners for heating soldering 

 tools in workshops, &c., are to be bought tolerably cheaply. As 

 a rule a spirit-lamp will not give sufficient heat, except for very 

 small tools not applicable for good sized joints. 



Expt. 48. To Bend and Cut Glass Tubing. Another matter 

 highly useful in the construction of apparatus is the cutting to 

 length and bending of glass tubes. For tubes not much bigger 

 than a stout quill (the kind mostly used) the cutting is 

 effected simply by drawing across the tube the edge of a triangular 

 file (which may be slightly wetted) so as to make a scratch ; by 

 pressing the tube with both hands as though you were trying to 

 bend it at the scratched part, it will generally break clean across 

 at the scratch (fig. 32) ; it is always safe to grasp the tube by means 

 of a handkerchief or towel whilst doing this in case it should not 

 break properly, so as to avoid possibly cutting the fingers. The 



Fig. 32. Cutting Glass Tube. Fig. 33. Bending Glass Tube. 



edges of the cut parts should be smoothed down slightly with the 

 file, otherwise they are apt to cut and injure corks when passed 

 through perforations therein. 



In order to bend the tubing, the best way is to hold the tube 

 horizontally in a " bat's wing " ordinary flat-flame luminous gas- 

 burner (fig. 33) (preferable to a spirit-lamp or Bunsen gas-lamp, 

 either of which may, however, be employed in default of a bat's 

 wing burner), slowly turning it round so as to heat it equally ; in 

 two or three minutes a length of some 3 inches is thus heated 

 sufficiently to form a neat regular bend on pressing the tube in 

 the proper direction. After removal from the flame, when the 

 bend is complete the glass should be held in the air a while by 

 hand or a clampholder to cool ; if laid on a table whilst hot the 

 table will be burnt and very probably the glass will crack at the 

 bend from the comparatively sudden chilling. When quite cold 

 the film of lampblack or soot sticking to the glass is wiped off 

 and the bend is complete. Care must be taken not to attempt to 



