128 A. W. Duff— Secondary Undulations 



close together as to defy copying, to clear cases of a definite 

 measurable period. Sometimes as many as 40 oscillations can 

 be counted. The mean periods obtained are* 4*7 m., 4*8 m., 

 4'8 m., 4'65 m., 4*7 m., 4 - 7 m. — final mean 4-7 m. Along with 

 these there occasionally occurs a series of much longer period 

 depending apparently on a state of high wind. The period in 

 such cases is difficult to determine accurately owing to the 

 other markings referred to. The following exceptionally clear 

 cases are of particular interest. On Oct. 15th, 1898, 11 regu- 

 lar oscillations gave a mean of 12*9 m. and on Oct. 16, 1898, 

 14 oscilations gave a mean of 12*9 m. In the latter case the 

 amplitude was at times a foot and the whole tide was elevated 

 1-J feet both at high water and at low water (a marked sign of 

 high wind). 



2. Souris, Prince Edward Island. Secondary undulations 

 are almost always present. The extent is usually only one or 

 two inches, at times three inches, occasionally swelling out to 

 seven inches and showing strong signs of the coexistence of 

 systems of different period. The only casesf in which the 

 periods were definite and determinable gave 22 - 5, 21*8, 21*2, 

 21*2, 22*0, 216, 20-0, 22'4, 24*5 minutes— mean 21-9 minutes. 



3. St. Peter's Bay, P. E. I. Secondary undulations are very 

 common but usually very irregular. At times the irregularity 

 shows evidence of the superposition of different systems. On 

 a very few occasions;); the undulations become regular, giving 

 mean periods of 19, 22, 21 m. — final mean 20 m. On another 

 occasion § seven very regular oscillations gave a mean period of 

 30 m. pointing probably to the conflicting system. The gauge 

 was only a month in operation. 



4. Charlottetown, P. E. I. (on an irregular shallow bay con- 

 nected by a narrow entrance with Northumberland Strait 

 between P. E. I. and JNL B.). Secondary undulations very rare 

 and irregular. 



5. Pictou, N. S. (at the eastern end of Northumberland 

 Strait). Secondary undulations are frequent and persistent 

 but of small extent; periods| 33, 31, 26, 24, 30, 30, 28— mean 

 29 m. The preceding were from the records of a large gauge 

 in the summer of 1896. In the following year a small gauge 

 replaced the large one and periods 1 ! were observed of 26, 27, 

 32, 31 m. — mean 29 m. as before. 



* July 4 (10), 3 (20); Oct. 3 (17), 1 (14): July 25 (40) Sept. 9 (7)— 1893. 



f July 8? (4), 17 (11); Aug. 17 (4), 24 (4), 29 (5), 29 (6); Sept. 20 (3), 19 (7), 



?(±). 



% Nov. 15 (5), 13 (4), 15 (10). 



§Nov. 16 (7). 



|| Sept. 7 (5); Oct. 27 (6); Nov. 1 (6); June 20 (4); June 27 (3); June 30 (3); 

 July 6 (5)— 1896. (Occasionally some doubt as to exact date.) 



^ July 7 (10); Sept. 21 (5), 23 .(5), 24 (8). 



