Chase.] 



288 



[December. 



order to obtain that approximation, it will be seen that I took, 1st, 

 the mean of the ranges and ratios for the three successive years ; 2d, 

 the ranges and ratios of the mean results of the three years ; 3d, the 

 grand mean of these two primary means. I could think of no other 

 method which would be so likely to destroy the eifects of changing 

 seasons and other accidental disturbances. 



The following table exhibits the eiFects of latitude on the aero- 

 baric tides. The differences between the theoretical and observed 

 ranges may be owing partly to the equatorial-polar currents, and 

 partly to insufficient observations : 



Station. 



Arctic Ocean, 



Girard College, 

 Washington, 

 St. Helena, 

 Equator, 



Mean 

 Range. 



•012 in. 



•060 



•062 



•066 



•082 



torial ratios bv 



•' R 



The theoretical ratios are determined by multiplying the equa- 

 The formula, p=z . — , (p indicating 



the ratio of the mean range to the mean height), gives 



Theoretical Ratio. Observed Ratio. 

 Latitude, 0° ^002 190 '002670 



Latitude, 78 37^ '000432 ^000404 



showing that the ratio is less near the pole and greater near the 

 equator than our theory indicates, a natural consequence of the cen- 

 trifugal force at the equator and the cold surface currents that pro- 

 duce the trade winds. 



The revolution of the sun around the great Central Sun must also 

 cause barometric'fluctuations that may possibly be measured by deli- 

 cate instruments and long and patient observation. The Torricellian 

 column may thus become a valuable auxiliary in verifying or rectify- 

 ing our estimates of the distances and masses of the principal hea- 

 venly bodies. 



Dr. Wood, requesting Prof. Cresson to take the Chair, 

 described the peculiarities of the growth of the olive tree in 

 Spain and its method of cultivation, reading from his journal 

 an interesting account of his tour through the olive-planting 

 districts. 



