BLOWING QUARTZ FIBERS. 



the cloth in diffuse sunlight at a larger angle of reflection it will be 

 found covered with fibers of various sizes and lengths, the heavier 

 ones, of course, coming from the cooler parts of the flame. Colored 

 spectacles will be found serviceable in this work. 



The handling of such fibers requires some dexterity, and in acquiring 

 it the manipulator generally develops some system of his own. The 

 writer has had the best success by employing two flexible glass rods, 

 of about 2 and 8 cm. length respectively, with a bit of shellac solution 

 on one end of each. The quartz fiber is secured from the cloth by 

 means of the longer glass rod, while the shorter one is permitted to 

 hang free from the other end of the fiber. Holding the radiometer or 

 galvanometer suspension in the right hand and the long glass rod in the 

 left, the shellacked end of the suspension is brought against the quartz 

 fiber, close to the long glass rod, which is then turned several times 

 around the suspension. A sudden pull severs the rod from the sus- 

 pension, leaving the quartz fiber, with the short glass rod at the other 

 end, hanging free. A hot wire is brought near the suspension (now held 

 vertically) to dry the shellac, care being taken that the shellac does 

 not become too hot, otherwise the fiber will drop off. The metal sus- 

 pension head having previously been laid at one end of a wooden tem- 

 plate, which is used to get the exact length of the fiber, the quartz 

 fiber is now laid across this head and the suspension is laid on the 

 template. The short glass rod hangs over the end of the template and 

 draws the quartz fiber taut. The fiber is pressed against the suspension 

 head (previously shellacked), the hot wire is applied, and the task is 

 completed. The manipulator then raises the wooden template into 

 the vertical position, and, if the lint has previously been burned off, the 

 suspension will swing free from it. By proceeding in this manner, 

 which takes less time than required to write this description, no tension 

 greater than the weight of the suspension is brought upon the fiber 

 and rarely is one broken in mounting. A glass tube, of a diameter 

 to hold the metal suspension head, mounted in a wooden block, is 

 serviceable in storing such a suspension and in carrying it from the 

 mounting table to the instrument. 



The diameter of such fibers, which of course make excellent cross- 

 hairs, has not been determined, and it will be sufficient to add that they 

 look blue in dim light. The finest fibers appear crinkled, as one 

 removes them from the cloth. The bow-and-arrow process will no doubt 

 produce just as fine fibers, but the present method is better adapted for 

 speed. As already mentioned, the method is not new, but to the 

 writer's knowledge no full description of the actual manipulations 

 involved has been published heretofore, and if this attempt will be of 

 service to any one interested in the subject its mission will be fulfilled. 



