APPENDIX V. 



NOTE ON BLOWING FINE QUARTZ FIBERS. 



The bow-and-arrow method of shooting quartz fibers invented by 

 Boys, as well as the method of heating a quartz bead to incandescence 

 in an oxyhydrogen flame and drawing it out into a fine fiber, seems 

 familiar to nearly everyone. Nevertheless, in making rapidly the finest 

 obtainable fibers, such as are necessary for radiometer and for light 

 galvanometer suspensions, there is one step in the latter method which 

 seems a novelty to so many investigators with whom the writer has 

 recently come in contact, that a description, with diagrams, is given 

 here, though there can not be anything new in the process, which seems 

 to be handed down by tradition rather than by recorded history. 



Fortunately we can now buy rods of vitreous quartz, and are no 

 longer obliged to build up rods from bits of pulverized quartz crystals 

 by holding them in the hottest part of the oxyhydrogen flame. By the 



Ox 



o 



c 



01 

 *\ 



O 

 o 



r* 



x 



Hyd 



FIG. 93. 



following method the manipulator can blow enough fibers in a few 

 minutes to last him many months, provided he stores them in a box 

 away from draughts and flies. 



To be brief, the oxyhydrogen or oxy-illuminating gas flame is regu- 

 lated to a length of 5 to 8 cm. A shallow box (5 by 50 by 100 cm.) 

 with a lid, lined with black canton flannel or simply a black cloth, is 

 placed vertically at a distance of about 35 cm. from the flame, which 

 is horizontal. The manipulator, facing the cloth, holds the rod of 

 vitreous quartz (i to 2 mm. diameter) in the hottest part of the flame, 

 as shown in fig. 93, which is a horizontal view. When the rod begins 

 to melt it is drawn apart in a horizontal direction, the one end toward, 

 the other end away from the cloth. At the point of rupture a fine fiber 

 will be drawn out by the flame, and the heated gases will drive it against 

 the cloth. The two melted ends are then stroked past each other as 

 rapidly as the manipulator desires, and each time a number of fibers 

 will be drawn out. The fibers are so thin that only the heavier incan- 

 descent ones will be seen in the flame and hot gases, but on examining 

 126 



