22 report — 1842. 



second, and the height of an unbroken wave was 27 feet above the surface level ! These 

 waves were breaking in iive and six fathoms. On the 1st of October the velocity of the 

 waves travelling at right angles to the wind, was 46' feet per second, the distance be- 

 tween the waves was 345 feet, and their height only 5 feet! 



On the Tidal P/tcenomena in the Bay of Fandy and the River de la Plata. 

 By Mr. Rook. 



On the Meteorology of the Province of Coorg, in the Western Ghats of 

 India. By Colonel Sykes, F.R.S. 



In offering a further contribution in support of an almost established law in me- 

 teorology, a few prefatory observations may be useful. Towards the end of the last 

 century it was remarked, in a series of barometrical observations made at Calcutta, 

 that there was a periodicity in the daily rise and fall of the mercury ; the barometer 

 throughout the whole year being highest between 9 and 10 a.m., and lowest between 

 4 and 5 p.m., the semi-diurnal oscillation however varying from - 030 to "150 or even 

 •170. Humboldt determined the same fact in South America, not only at the level of 

 the sea, but on the elevated plateaux of the Andes, finding however that there appeared 

 to be a gradual diminution of the oscillations between 9 — 10 a.m. and 4 — 5 r.M. in 

 2)roportion to the ascent or elevation above the level of the sea. These phenomena 

 led to hourly barometrical observations, and it was found that whereas during the 

 day there was a maximum pressure between 9 and 10 a.m. and a minimum pressure 

 between 4 and 5 p.m., so during the night there was a maximum pressure between 

 10 and 11 p.m. and a minimum pressure about 4 or 5 a.m.; thus establishing two 

 ascending and two descending waves or tides in the atmosphere during the twenty- 

 four hours. My meteorological observations, carried on for several years in the 

 Deccan at 2000 feet above the sea, and published in the Philosophical Trans- 

 actions, were entirely confirmatory of those made by Humboldt ; there never having 

 occurred a single instance, whatever the season of the year, wet or dry, hot or cold, 

 in which the barometer was not higher at 9 — 10 a.m. than at 4 — 5 p.m. The same 

 facts were obtained from the Nilgherry mountains at 8000 feet above the sea — by 

 Colonel Sabine from the coast of Africa — and from numerous other places within the 

 tropics. From the irregular movements of the barometer beyond the tropics, the phe- 

 nomena escaped observation for some time, but of late years numerous careful ob- 

 servations and a series of averages have eliminated the same facts which characterise 

 the tropics, the amount or range of the semidiurnal oscillation, however, gradually 

 diminishing from the equator towards a parallel not yet determined, in very high 

 latitudes (but which is beyond 70° N-.), where the hours of maximum and minimum 

 pressure are not the same as at the equator. Mr. Snow Harris's singularly uniform 

 successions of curves of average pressure of the barometer at Plymouth for several 

 years, show the same hours of maxima and minima that 1 found in the Deccan ; and 

 by a series of observations transmitted to Colonel Sabine from Finmarken, in latitude 

 70° N., the average height of the barometer is still found in that high latitude to be 

 greater at 9 a.m. than at 3 p.m., the mean annual temperature of the place of obser- 

 vation approximating to the freezing point. 



Although there is a perfect accordance in the hours of maximum and minimum 

 pressure within and without the tropics, there is not the same accordance in the ex- 

 tent or range of the semidiurnal oscillation of the barometer. In the tropics it is 

 considerable ; in high latitudes very small ; and from such observations as have been 

 made in intermediate latitudes, grounds are afforded for the belief, that the amount 

 of the semidiurnal oscillation gradually diminishes from the equator toward the 

 poles, and that the time of the occurrence of maxima and minima are reversed, 

 the exact latitude where this change takes place not being yet satisfactorily de- 

 termined. 



With these prefatory' observations I may state, that the meteorological observations 

 obligingly communicated to me by Dr. Blest of the Madras army, from a new locality 

 in the Western Ghats, are entirely confirmatory of those I made in the Deccan re- 

 specting the movements of the barometer. 



