14 REPORT 1844. 



A Comparison of the Rain which fell at Florence Court, the seat of the Earl 

 of Enniskillen, from July 6th, IS^S, to July 6th, 184<4', tvith that which fell 

 at Belfast during the same period. By W. ThOiMPSON, Esq. 



Belfast and Enniskillen are seventy-two miles apart ; one towards the east, the 

 other towards the west, of the north of Ireland. 



The total depth of rain which fell, was inches. 



At Florence Court 40*6 



At Belfast 30-34 



Monthly average at Florence Court 3*38 



Monthly average at Belfast 2*53 



The greatest monthly fall, was 



At Florence Court, in November 6'051 



At Belfast, in October 5-046 



The fall at Florence Court during October 5*943 



The fall at Belfast during November 3-943 



The least fall happened in May 1844, at both places. 



At Florence Court 0-041 



At Belfast 0-273 



The only singular discrepancy which occurred was, that in the month of September 

 1843, only 0-51 inch fell at Belfast, while at Florence Court, in the same month, 2-759 

 fell. This, when explained by Lord Enniskillen's steward, who keeps the register, 

 was found to arise from a very heavy fall which took place in one day. The month 

 was generally very dry at both places. 



On the Orthockronograph, inveyited by the late Mr. Lowman. 



This is a portable instrument for ascertaining the time at any place, by one or 

 more observations, previous and subsequent to the sun's passing the meridian ; the 

 circle or circles on the silvered plane being correspondent with the arc described by 

 the sun in its apparent diurnal passage through the heavens. In taking an observa- 

 tion, the upper plate is adjusted so that the reflexion of the sun's rays through the 

 circular aperture cuts at its edge one of the circles on the silvered plate ; the time 

 indicated by the watch or clock is then noted, and the instrument left stationary, 

 until the sun's image, after traversing the plate, has returned to the same circle, and 

 again the time marked as accurately as possible. 



The interval between the two observations will depend on the time when the first 

 is made, and should not be less than three hours : the results thus obtained are 

 added together, and divided by two, a correction made for the alteration of the sun's 

 declination during the interval, and the ditference between this result and twelve 

 hours will show the clock's error as compared with solar time ; lastly, the equation 

 of time will give the error from mean time. 



The Mean Year, or Solar Variation through the Seasons of the Barometer in 

 the Climate of London. By Luke Howard, F.R.S. [Plate XLI.] 



The variation of the barometer through successive months in any given year has 

 been sufficiently shown to be connected with the lunar influence, by which the tides 

 of the ocean are governed ; and this influence, until more fully investigated, will 

 continue to present difiiculties in the use of the barometer as a weather-glass — the 

 atmospheric tides requiring for this purpose to be set aside while we attempt to pro- 

 gnosticate results from currents of another nature. It may be useful for this purpose 

 to have tables of the variation of the barometer (in connexion with the prevailing 

 winds) in which the lunar influence is set aside by proper averages. 



Such a set of tables are here presented ; the calculations being made upon data 

 to be found in the author's long-published work, 'The Climate of London,' and the 

 years chosen, as most convenient for the purpose, extending from 1813 to 1830. A 

 near approach is thus made to the cycle of 18^ years, in the course of which it is 

 presumed that the effect on our atmosphere of the various positions of the earth and 



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