130 7. C. Mendenhall—Acceleration of Gravity at Tokio, Japan. 
This result is slightly greater than that given by many of the 
formulas for computing the value of “g” in any latitude. 
An excellent opportunity is offered in Japan for measuring 
the force of gravity at a considerable height above the sea level, 
in the great extinct voleano, Fujiyama, which reaches a height 
of between 12,000 and 18,000 feet. An excursion is being 
arranged for the purpose of making this determination during 
the coming summer. For this purpose what may be called an 
‘invariable’ pendulum is now being vibrated in the place at 
which the above result was obtained. Its period will be care- 
fully ascertained here before carrying it to the mountain, then 
on the top of the mountain, and again here after it has been 
brought back. 
Nearly all of the labor of the above determination had been 
The data furnished in the paper are by no means as complete 
as would be desirable for a thorough discussion of its value, 
but much may be learned by an examination of what it does 
contain. 
dulum has been almost universally made use of since. The 
great objection to the use of a long pendulum is the difficulty . 
of measuring it im place. Messrs. Ayrton and Perry measured 
their pendulum by placing it in a horizontal position, and 
stretching it by allowing the end near the ball sy hd over a 
wheel with very little friction. The length was obtained by 
comparison with a bar one meter long, and as this bar must be 
