60 



MEMOIKS OF THE NATIONAL ACADEMY OF SCIENCES. 



tbougUt ii tabiilatiou of the hourly .speed of the vessel might give some imlicatioii of the diurnal 

 course of the wiud velocity. The following table was therefore made, which gives the hourly 

 speed, taken from the ship's log, through the courtesy of Cajitaiu Carpenter. It will be seen that 

 the mean values show a distinct increase in the evening and a corresponding decrease in the 

 morning, with the maximum at 11.00 p. m. and the minimum at 11.00 a. m. It seems fair to attribute 

 this to the diurnal variation in the wiud velocity. There is (juite an unexpected regularity in the 

 progression when we consider the approximate nature of the method. If not attributable to 

 diurnal change in the wind itself, it yet indicates a diurnal change in the eli'ect of the wind upon 

 the sails, and is therefore of interest. 



Hourly speed of the U. 8. 8. Hartford, March 23-April 13. 



