TIDAL OBSERVATIONS 



575 



Tepliiz £ay.^^e.s\x\ts from 58 days, April i, oh to May 28, 23h, 1904, mean local civil 

 time, to wkich is added the results obtained by the expedition of the Duke of Abruzzi, 1899- 

 1900, as taken from the scientific results of his polar expedition, published in Milan, 1903. 



The tides discussed by the Duke of Abruzzi consisted of three short series — September 19 

 to October 17, 1899, March 16 to April 3, 1900, and June 3 to 27, 1900. The record was 

 very defective, especially for the first series, where only a few readings were obtained on most 

 days. The values given above are the corrected mean results, taken from his published 

 report without change, other than converting meters into feet and minutes into tenths of 

 degrees. For the most part there is a very satisfactory agreement between the results of the 

 two analyses. 



I/UNiTiDAL Intervals 



The tide follows the moon much more closely than it does the sun, so that there is a ten- 

 dency for the tide to occur when the moon is in a given position in the heavens. The differ- 

 ence between the time of tide and the time of the moon's transit or meridian passage is called 

 the hmitidal iiiterval for the station, t Both upper and lower transits of the moon are usually 

 compared with the time of the first high water and first low water which follows the given 

 transit ; hence ! we may express the operation as follows : 



High-water lunitidal interval = H WI = Time of H W— ])'s transit ' ^ (i) 

 l/ow- waiter- lunitidal interval = I, WI = Time of LW — })'s transit (2) 



