V E L 



VARIATION diurnal. 



The horizontal needle, besides its annual change in direction, is also 

 subject to a daily change, amounting at certain seasons of the year to 

 about 14' or 15'. According to the most recent observations, it appears 

 that the needle attains its maximum direction eastward about 7 o'clock, 

 or y 2 past ? in the morning, that it continues moving westward till two 

 o'clock in the afternoon ; it then returns to the eastward till the even- 

 ing; it has then again a slight westerly motion, and in the course of the 

 night, or early in the morning 1 , attains the bearing it had 24 hours before, 

 or very nearly. It has also been admitted by all observers, that the daily 

 motion during the summer months is the greatest, and during the win- 

 ter months the least ; but the particular month in the summer when the 

 daily change is the greatest, is a little uncertain. Canton and Wargen- 

 tin make it about July j but Col. Beaufoy found it greater in June and 

 August than in July. 



Table of the mean monthly diurnal variation of the compass from April 

 1817 to March 1819. By Colonel Beaufoy, at Stanmore Heath. 



VELOCITY angular. See Central Forcet. 



VELOCITY paracentric, See Central Force*. 

 33ft 



