180 LIEUT-COLONEL SYKES ON THE ATMOSPHERIC TIDES 



ber and January *. The means of four years' observations, from 1827 to 1830 inclu- 

 sive, made by Mr. Hudson at the Royal Society, give two maxima and two minima 

 in the year, the former occurring in February and October, and the latter in April 

 and September. Professor Forbes's observations in the same years at Edinburgh give 

 a mean maximum in the winter months, December, January, and February, of 29-442 

 inches, and a mean minimum in spring, March, April, and May, of 29*0359 inches. 



The annual mean height of the barometer at Poona was 27*9254 inches ; at Ma- 

 dras for twenty-one years it was 29*958 inches ; at Calcutta the means of three years 

 make it 29*764 ; M. Arago, at Paris, by nine years' observations, reduced to the level 

 of the sea, makes the mean height 29*9546 inches, almost identical with the mean 

 height at Madras. 



The climate of Dukhun is subject to very considerable variations of temperature, 

 more, however, in the diurnal than in the monthly or annual ranges ; indeed, less so in 

 the last particular than in Europe. In 1827, the extreme range of the thermometer 

 at Edmonton was 75° Fahr. (83° highest, 8° lowest) ; at Cheltenham it was 64°*5 

 (80°*5 highest, 16° lowest) ; in 1828 at Edmonton it was 61° (83° highest, 22° lowest). 

 These extremes are even exceeded on the continent of Europe. In St. Petersburgh 

 the thermometer has been as low as 35°*7 below zero, and as high as 91°* 4, the range 

 therefore 127°' 1. At Berne in Switzerland the range has been from 24° below zero 

 to 95°*25 Fahr. The extreme range of my thermometer in 1 826 was from 93°*9 to 

 40°*50 or 53°*4 ; the former occurring on the 12th of March at 4 p.m., and the latter 

 on the 15th of January at sunrise. In 1827 the extreme range was from 96°-8 to 48°, 

 exhibiting a difference of 48°*8, the maximum being on the 28th of March at 4 p.m., 

 and the minimum on the 12th of December at sunrise. In 1828 the maximum 

 occurred on the 7th of May at 4 p.m., being 101°, and the minimum 56° on the 16th 

 of February and 4th of December at sunrise, the range not exceeding 45°. I have to 

 remark, however, that for a short time on the 7th of May, the thermometer rose to 

 105° (this was at the source of the Beema river, at a height of 3090 feet above the 

 sea), the highest record of the instrument I have ever had in Dukhun, in the shade, in 

 very many years' observations. These occasional manifestations of extreme heat would 

 appear not to be confined to the equatorial regions, there being many similar in- 

 stances in the temperate zones. At Montpelier in France, in 1823, the thermometer 

 stood for some days at 100° Fahr. In Paris, in 1793, it was at 99°*6 ) and Humboldt, 

 in his Personal Narrative, mentions, on the authority of Arago, it being even 101°* 12 

 Fahr. at Paris. The range of the thermometer in Paris, between 1793 and 1795 in- 

 clusive, was from 8°*6 below the freezing-point of Fahr. to 99°*6 or 81°. 



The monthly means do not differ much from each other in Dukhun. In 1826 the 

 difference between the means of the hottest month, May (83°*28), and the coldest, Ja- 



* January, 0""»-56045 ; Temperature 15°-7. June, 0'"'"-56124; Temperature 15°-1. 

 December, 0""»-56013; Temperature 15°-0. July, 0"""-56134; Temperature 14°-2. 



Humboldt, Personal Narrative, vol. vi. part ii. page 743. 



