334 proceedings: philosophical society 



certificates of the watches' performances. In conclusion, some results 

 of pocket tests of watches made by Mr. F. M. Bookwalter were shown 

 and the principal uses and value of a laboratory test in later use and care 

 of one's watch pointed out. The paper was discussed by Messrs. 

 Bowie, Fischer, and Wells. 



Mr. W. P. White then spoke on Calorimeter jacket design The two 

 difficult features of calorimetric work are temperature measurement and 

 cooling rate determination. The more nearly the cooling rate is propor- 

 tional to change in temperature, the better is the result. The general 

 conclusion was reached that cooling rate has not so much to do mth 

 distance between two surfaces of calorimeter as with shape of cavity. 

 The paper was discussed by Mr. Dickinson. 



Mr. W. Bowie communicated informally the initiation by the Cana- 

 dian government of an extended gravity survey of Canada. He also 

 stated that the Coast and Geodetic Survej^ has found that Western 

 Union noon time signals may be relied upon to 0!l ; this means that cost 

 of gravity work may be much reduced, there being no further need of 

 field time observations. At 10 p.m. the meeting adjourned. 



The 740th meeting was held on April il, 1914, at the Cosmos Club, 

 Vice-President Eichelberger in the chair; 42 persons present. 



Mr. W. D. Lambert presented a paper entitled The motion of falling 

 bodies. The author discussed the effect of the Earth's rotation on the 

 motion of a body falhng from rest and particularly as regards the com- 

 ponent of the motion parallel to the plane of the meridian. The problem 

 was treated in two ways, first by considering the falling body as a satellite 

 of the Earth and, second, by the method of moving axes. The first method 

 is not limited to short intervals of time but neglects the effects of the 

 Earth's equatorial protuberance. If the displacement parallel to the 

 plane of the meridian be expanded in powers of time, t, and terms involv- 

 ing powers of co higher than ox^ be neglected, co being the angular velocity of 

 the Earth's rotation, then there is no term in the expansion with a 

 power of t lower than the sixth. The second method may be arranged 

 to take account of the Earth's ellipsoidal form, the changes in the direc- 

 tion of gravity being allowed for in successive approximations. The 

 second method verifies result of the first as to term in w and brings out a 

 very small southerly deviation (reckoned from the direction of gravity 

 at the starting point) due to the ellipsoidal form of the Earth. The result 

 may be analyzed in the following manner, speaking for the northern 

 hemisphere: The direction of gravity changes during the fall of the body, 

 first from the oliange in centrifugal force, which tends to give a northerly 

 deflection; second, from the change in attraction of the equatorial protu- 

 berance, which tends to give a southerly deflection. There is, however, 

 also a relatively large easte^'ly deflection, and the velocity with which 

 this takes place gives rise to an apparent force due to the Earth's rota- 

 tion and tending to swing the easterly deviation to the right (northward) ; 

 this is just sufficient to neutralize that arising from change in centrifugal 

 force and leaves outstanding that due to Earth's equatorial protuberance. 



