168 LIEUT.-COLONEL SYKES ON THE ATMOSPHERIC TIDES 



great masses of clouds, and distant thunder and lightning ; a storm threatened, but 

 did not take place. The same appearances continued daily until the 21st, on which 

 day there was a hail storm, whilst the thermometer stood at 86°'3. On the 23rd 

 there was another hail storm and thunder : this weather continued to the end of the 

 month, and the daily oscillations were so great as to make the mean exceed that of 

 any other month in the year. Here there could be little doubt of the oscillations 

 being affected by the state of the weather. In 1827 the maximum oscillation of '1892, 

 (difference of thermometer attached +10°, dewing-point 37° from saturation, wind 

 none,) took place on the 7th of March, and the weather was free from any of the 

 indications before noticed ; but on the 9th of March there was a little lightning 

 and some drops of rain. In 1828 the maximum oscillation of •1856, (difference of 

 thermometer attached +10° 8', no wind, and clear sky,) took place on the 2nd of 

 January. In 1829 the maximum oscillation was on the 26th of February, and amounted 

 only to "1648, difference of thermometer +11° 5', wind light east, and clear sky. 



In 1827 the minimum oscillation of the year occurred on the 7th of August, between 

 9 A.M. and 4 p.m., amounting to '0150; difference of attached thermometer — 0°'8, light 

 west wind, sky quite overcast, but no rain, although the dewing-point was only 3° 

 from the point of saturation. A nearly similar oscillation, *0153, thermometer +5°*2, 

 took place on the 29th of the preceding May, with a violent west wind and clear sky, 

 and no dew-point obtainable at 4 p.m. In 1828 the smallest diurnal oscillation of 

 •0155, thermometer +2°*3, took place on the 19th of October during a gentle rain 

 and light S.W. wind. In 1829 the smallest oscillation was '0281, thermometer +0°*9, 

 on the 2nd of July, with a partially clouded sky and fresh W.S.W. wind, the hygro- 

 meter being 6° from the point of saturation. On the 21st of March the next smallest 

 oscillation of the year took place, with a misty sky, light west wind, and air very dry. 

 In 1830 the minimum of the year was also in July, amounting to '0327, the thermo- 

 meter being half a degree lower at the minimum than at the maximum hour ; sky 

 overcast, no rain, wind light west, hygrometer 8° from the point of saturation. On 

 the 20th of March there is also a small oscillation of -0493, thermometer +9°'9, sky 

 clear, fresh west wind, and hygrometer 29° from the point of saturation. I have been 

 particular in noticing the state of the weather and the winds, &c., at the periods of 

 these extreme oscillations, as Mr. Snow Harris of Plymouth suggests that the atmo- 

 spheric tides may be influenced by the force of the wind, whilst others refer them to 

 hygrometric causes. 



The mean of the diurnal oscillation of the barometer in Dukhun from 9 — 10 a.m. 

 to 4 — 5 P.M. for 1827 was '1025, mean range of attached thermometer between the 

 two periods +5°-99. In 1828 it was ^1093, thermometer +6°'36. In 1829 it was '0991, 

 thermometer +3°-92. The smallness of the range both of barometer and thermometer 

 in this year is attributable to three months' observations having been taken at an 

 elevation of nearly 4000 feet above the sea. In 1830 the barometers were stationary 

 for the whole time at Poona, and I look upon these observations as affording the 



