T. C. Mendenhall—Acceleration of Gravity at Tokio, Japan. 125 
objection to the process on account of resistance is removed. 
Indeed it is in the possibility of determining these fractional 
parts of a second at the beginning and at the end, that the 
merit of this method consists. The chronograph used in these 
determinations is by Alvan Clark and Sons, and for uniformity 
of speed it is everything that could be desired. The line made 
by the pen is sharp and clear. The length of one second on 
the sheet is about 8 mm., so that it can be easily measured with 
rom either knife edges equal to each other, is a matter of con- 
siderable difficulty and involves much labor. In the present 
instance no attempt was made to secure a closer agreement 
between the two periods than that of those recorded below, for 
the reason that the difficulties in the way of obtaining the 
exact length of the pendulum were such as to make any greater 
degree of accuracy as far as time is concerned unneces ‘ 
There being at that time no standard of length in the posses- 
sion of the University, recourse was had toa standard bar three 
meters in length, made by Troughton, belonging to the Depart- 
ment of Public works. “As the pendulum was approximately 
