172 LIEUT.-COLONEL SYKES ON THE ATMOSPHERIC TIDES 



leshwur, observed at both these periods for eight months ; and Mr. Dalmahoy, at 

 Kotagherry, between 9 — 12 p.m. and a little before sunrise, observed for five months. 

 On the 30th of November 1828, at Poona, the a.m. minimum tide turned at 4^" 30°* 

 A.M., and the maximum nocturnal tide at 10^ 30™ p.m.; the fall between these periods 

 being '0150, and the difference of attached thermometer — 7°'6. The other tides of 

 this day were a rise of -0572, thermometer +9°-0, from 4^^ SO'" a.m. to 9^ 30™ a.m. ; 

 fall from 9^' 30™ to 4 p.m. -1330, thermometer +3°*4, and a rise of -0908, thermome- 

 ter — 11°'0, from the last hour to 10^ 30™ p.m. The mean of eighteen days in Sep- 

 tember at Poona, in 1827, gave a rise of -0753, thermometer — 5°'l, from 4 — 5 p.m. 

 to 10 — 11 P.M., and a fall of '0254, thermometer ^l°-37) from 10 — 11 p.m. to sun- 

 rise. The rise from the latter hour to 9 — 10 a.m. was '0352, thermometer -|-3°*65, 

 and the fall from 9 — 10 a.m. to 4 — 5 p.m. was '0844, thermometer +2°'82. For 

 twenty-one nights in October the fall from 10—11 p.m. to sunrise was only "0010, 

 thermometer — 2^*39 ; the rise from 4 — 5 p.m. to 10 — 11 p.m. '0745, thermometer 

 — 4°*76. But for nine nights in November the nocturnal a.m. tide occurred with a 

 contrary sign, the barometer being -0052 less, thermometer — 10°-2, at sunrise than 

 at 10 — 11 P.M. The maximum night tide, however, appears with the proper sign, the 

 rise being -0801, thermometer — 1 ]°65. On the 3rd of November of the following year 

 the A.M. minimum tide appears with the proper sign, the fall being '0040, thermome- 

 ter — 4°*0; and the rise from 4 — 5 p.m. to 10 — 11 p.m. was '0714, thermometer — 6°-5. 

 In the above, although we find great discrepancies in the fall from 10 — 11 p.m. to 

 sunrise, we yet observe great uniformity in the nocturnal rise from 4 — 5 p.m. to 

 10 — 11 P.M. with a falling thermometer. Dr. Walker found the mean nocturnal a.m. 

 tide for eight months to be -0180, thermometer — 1°'68 ; and the rise from 4 — 5 p.m. 

 to 10 — 11 P.M. to be '0439, thermometer --5°*58. Mr. Dalmahoy, at Kotagherry, 

 from 9 — 12 p.m. to a little before sunrise, for four months, found the mean fall to 

 amount to '0433, and the rise from sunset to 9 — 12 p.m to be '0430. Mr. Prinsep, 

 F.R.S., in a voyage from Calcutta to Bombay, during thirty-two days found the ba- 

 rometer fall '0220 from 10 p.m. to sunrise, and rise '0440 from sunrise to 10 a.m. ; fall 

 •102 from 10 a.m. to 4 pm., and rise '0800 from the last hour to 10 p.m. Observa- 

 tions taken hourly at the Madras Observatoiy, every tenth day and night, make the 

 night tide from 10 p.m. to 4 a.m. to amount to '035, and the 4 a.m. to 10 a.m. tide to 

 be '047 ; the other two tides being respectively '079 and '063. The smallness of this 

 maximum diurnal tide appears very anomalous, considering that Madras is in a low 

 latitude and at the level of the sea. 



In opposition to the above facts. Dr. Russell, at Boorhanpoor, gives a nocturnal 

 minimum tide with a contrary sign, or a n^e instead of a, fall of 0200, between 10 p.m. 

 and 5 a.m.; and in observations of Dr. Royle, at Saharunpoor in India, at 1000 

 feet above the sea, and of Fray Juan, at Vera Cruz, the nocturnal tide appears 

 in the monthly means so often with a plus instead of a minus sign, that the annual 

 mean establishes this tide only by '001 at Saharunpoor, and by -002 at Vera Cruz. 



