366 



Meteorology : variations of the Barometer. 



[Oct. 



purpose j but the Calcutta Journal for August 1833, gives the result of 

 six years' observations made at Singapur, by Captain C. E. Davis, as 

 follows : — 



Here too (it is almost needless to observe) the variations of the baro- 

 meter can be accounted for by a formula, similar to that employed in 

 Calcutta and Madras, save that the value of x will necessarily be very 

 small. That this formula should agree thus well with three independ- 

 ent registers, renders it highly probable, that the distance of the Earth 

 from the Sun does, under certain circumstances, affect the state of the 

 barometer. Now the influence of the Sun upon the Earth on the first of 

 January, is to its influence on the first of July (by reason of its relative 

 distances at those times) as 1032 ; 968; the effect of which is to create 

 a tide, or to produce a higher state of the barometer, in January, than in 

 July — the circumstances to which we allude are, the nature of the situ- 

 ation, with regard to its proximity to continents or seas, and its latitude. 



In the middle of a continent, or large island, for instance, we should 

 expect a very different result from that of a place situated upon the sea 

 coast, or from that of a small island ; and a further considerable allow r - 

 ance (due to the latitude) would probably be necessary for the obliquity 

 under which the Sun's rays enter the atmosphere at any place. Leaving 

 this last cause out of the question, as being likely to interfere but little 

 with the three cases under consideration, we find the location of 

 Singapur to be insular, or to differ but little from that of a spot in the 

 middle of the ocean ; we, consequently, should only expect a small 

 amount of correction : whereas at Calcutta (which is surrounded by 

 land) we should expect the largest amount of correction; and at 

 Madras (which is situated upon the coast) a correction of medium 

 amount, only, should be expected. Now although these expectations 

 are borne out by the results before obtained, still it would be rash, 

 in this early stage of the enquiry, and upon so few results, to enter- 

 tain any opinion beyond a suspicion. Under these circumstances, it on- 

 ly remains for me to apologize for this intrusion, when so ill equipped ; 

 and to explain that my only motive for so doing, is to shew how impor- 

 tant it is, to be exact in barometrical measures, and, by exhibiting how 

 deficient we are in meteorological materials, to attract a further atten- 

 tion to the subject. 



MEAN HEIGHT AT 6 A. M. 



January. 

 February 

 March . . 



April 



May 



June, 



29.947 July 



.933 August 



.920 September 



.920 October 



.897 November 



.890 December 



.908 

 .895 

 .918 

 .912 

 .913 

 .932 



