26 R. G. PERKINS 



DESCRIPTION OF PLATES 1 AND 2 



The numbers on both plates refer to the same parts. 



1, Main frame containing clock and with gutter for water seal. The number 

 in the detailed print lies in the gutter. 



2, Cover over clock with openings for shafts and regulator. 



3, Revolving table turning once in twenty-four hours. 



4, Clamp for Petri plate, with vertical and horizontal adjustments to fit any 

 plate from 2 to 4 inches in diameter. 



5, Vertical shaft with rack to fit pinion adjustment under No. 4. 



Note. — This rack and pinion was taken from an old microscope. The open- 

 ings in No. 2 should be covered during use by an oiled felt washer to keep the 

 steel parts of the clock from rusting in the saturated atmosphere. 



