9 6 



Laboratory Arts 



from a jet such as that figured, owing to disturbing eddy currents 

 being produced behind the projecting portions. A properly con- 

 structed jet should require little or no adjustment of the orifice after 

 making, the contracted portion leading by a single and even curve 

 to the correct-sized orifice. This is easily attained by allowing the 

 tube to thicken in the flame before pulling out, Fig. 84 (fl), and by 



(CL) 



FIG. 84. Stages in making a wash-bottle jet. The jet shown in (b} is too 

 wide, and to be closed must be treated so as to produce (c), which will 

 not eject an even stream. If (a) be pulled out correctly, a jet shaped as 

 Fig. 83 (3) will result, and will need no constricting of the orifice. 



pulling very slowly at first, giving the glass time to partly solidify 

 before finally shaping. A little experience will soon show the 

 exact amount of latitude possible, and any desired shape and 

 diameter of jet may then be produced at will. 



EXERCISE 2. To close the end of a tube. 



(a) Rounded. Proceed as in Exercise I, producing a jet. Heat 



withj a finely pointed flame at 

 the point A, Fig. 85, and pull 

 off sharply the thinner portion, 

 when the glass is well softened. 

 Turn the glass to a more acute 

 angle to the flame, and heat the 

 end until the glass shows signs 

 of collapse. Blow gently to 

 prevent this, and by alternate 

 blowing and heating, always 

 continuing the rotation, shape 

 the tube to the desired hemi- 

 sphere, the walls being equally 

 thick throughout, Fig. 85 (i). 



(b) Flattened. By heating the 



end of the tube so produced in the side of the flame, and main- 

 taining the rotation, the glass maybe permitted to collapse, leaving 

 a flattened] interior, while the hemispherical exterior is preserved, 



(2) 



FIG. 85. 



(3) 



