THE GRAPHIC METHOD 79 



white shellac in 95 per cent alcohol, 1 and hung 

 up until the alcohol is evaporated. The soot 

 will thus be coated over and held in place by 

 a thin layer of shellac, and the record will be 

 secure. 



The Kymograph. The improved kymograph 2 

 is shown at the right of Fig. 19, in which it is mounted 

 as part of the long paper device. It consists of a 

 drum revolved by clockwork and also arranged to be 

 more rapidly revolved or " spun " by hand. 



The drum is of aluminium, cast in one piece 

 turned true in the lathe to a circumference of 50 cm. 

 The height is 15.5 cm. The weight is about 600 

 grams. The drum slides upon a brass sleeve in bear- 

 ings 1.1 cm. deep (to prevent "sidelash"), and is 

 held at any desired height by a spring clip. The 

 sleeve ends in a friction plate, which rests upon a 

 metal disk driven by the clockwork. Sleeve and 

 friction plate revolve about a steel shaft which passes 

 through both the heavy plates containing the clock- 

 work, and is securely bolted to the bottom plate. 

 The sleeve bears upon the steel shaft only by means 

 of " bushings " at the ends of the sleeve, thus securing 



1 To make this solution, the alcohol should be allowed to 

 stand on the shellac a month or more before using. A satisfac- 

 tory solution may be made in twenty-four hours by dissolving 

 375 grams of rosin in 2500 c.c. of alcohol. 



2 Introduction to Physiology, 1901, p. 51. American Jour- 

 nal of Physiology, 1903, viii, p. xxxvii. Ibid., 1904, x, p. 

 xxxix. Science, 1906. 



