174 LIEUT.-COLONEL SYKES ON THE ATMOSPHERIC TIDES 



in latitudes more or less near the equator, it seemed to him that the extent of the 

 variations diminished very little with the elevation of the spot. Mr. Colebrooke re- 

 marks, that in the interior of India the periodicity of the tides is manifest, and inde- 

 pendent of the variations of the temperature and the seasons of the year. My obser- 

 vations, on the whole, tend to strengthen the opinions of Messrs. Humboldt and 

 Colebrooke. 



I found the stationary/ period of the tides to vary from nil to one hour and a half. 

 With respect to the maximum diurnal tide, it appears by the accompanying Table 

 that it never turned before 9 a.m. or after 10^ 20™ a.m. during the whole of 

 the year 1830; the seasons therefore were inoperative; and this is confirmatory of 

 Mr. Goldingham's observations at Madras in 1823, although no great reliance can 

 be placed upon them, from their having been made onli/ every tenth day : confirmatory 

 also of Margue Victor's observations made for years at Toulouse. I found the maxi- 

 mum diurnal tide (indeed all the tides) to oscillate in its time of turning, and in its 

 stationary period between the hours stated, without relation to any change in the 

 attached thermometer. On the 5th of February the tide turned before 10 a.m. ; on 

 the 14th it turned at 10^^ 20™ ; on the 11th of March at 9'' 15™ ; on the 19th not be- 

 fore 10 A.M.; April 11th at 9^ 30™; April 17th at 9^ 45™; on the I4th of June it 

 turned at 9 o'clock ; on the 10th of June at 10 o'clock ; and similar anomalies occur 

 in the following months. The stationary periods of the maximum a.m. tide range 

 from to 45 minutes, and the Table shows several instances of the latter. The fall 

 of the barometer in equal periods of time after the turn of the tide presents irregu- 

 larities. On the 1 1th of March the fall was '010 in 30 minutes : on the 1 1th of April 

 in 30 minutes it was only "001. 



The afternoon tide has the same irregularities as the preceding. It never turned 

 before 4 p.m., and in a few instances only after 5 p.m. On the 5th of February the 

 tide turned at 4 p.m. ; on the 8th at 4^ 30™ ; on the 20th of August at 5 p.m. ; on the 

 4th of October at 4 p.m., &c. 



The stationary period was from to 45 minutes ; but of the latter there is only one 

 instance in the Table, although there may be more in the registers, as the extracts 

 were taken at random. On the 9th of February there is a curious instance of the tide 

 turning at 4*^ 15™ p.m. ; then rising -004 to 4** 30™, continuing stationary until 5 p.m., 

 and then resuming its rise. As in the morning tide, the movements of the barometer 

 were not equal in equal times. On the 5th of February the tide rose only -002 in 



board ship in the terrible hurricane of the 27th and 28th of August 1794, found that the column of mercury- 

 fell only '4448 (11"""*3). — Personal Narrative, vol. vi. part ii. page 794. 



I am enabled to strengthen this assertion by the following extract from the log-book of the Duke of Buccleuch, 

 Captain Henning, from Calcutta to London, in January 1833, during a frightful tempest of two days' duration 

 off the Isle of France : — 



" 21st. Lat. 24° 31'. Long. 61° 49'. Bar. max. 30°00. Bar. min. 29°-60. Temp. 80|°. 



22nd. Lat. 25° 39'. Long. 57° 32'. Bar. max. 29°-76. Bar. min. 28°-94. Temp. 82°." 



The whole fall, therefore, amounted to no more than one inch and six hundredths in the two days. 



