132 Proceedings of the British Association. 



are luted. Col. Everest mentioned, that the best material for the valves 

 of an air-pump was the swimming bladder of a fish. 



A Comparison of the Rain which fell at the seat of the Earl of Ennis- 

 killen, Florence Court, from July 6th, 1843, to July 6th, 1844, with that 

 which fell at Belfast during the same period, by Mr. W. Thompson. — 

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



east, the other towards the west, of the north of Ireland. 



Inches. 

 The total depth of Rain which fell, was 



At Florence Court, 40-6 



At Belfast 30 34 



Monthly average at Florence Court, 3-38 



Belfast, 2-53 



The greatest Monthly fall, was 



At Florence Court, in November, 6051 



At Belfast, in October 5-046 



The fall at Florence Court, during October 5-943 



„ Belfast, during November, 3*943 



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



At Florence Court 0041 



At Belfast 0-273 



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

 of September, 1843, only 051 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 gene- 

 rally very dry at both places. 



* On the Irregular Movements of the Barometer,' by T. Hopkins. — 

 Mr. Hopkins maintained that the irregular movements of the barometer 

 arise, not from alterations of surface temperature, but from the con- 

 densation of aqueous vapour, and the consequent formations of rain. 

 This (he said) caused local heatings of the atmosphere and considerable 

 reductions of its pressure in the locality, particularly in the colder lati- 

 tudes. Within the tropics, the barometer does not ordinarily fall as 

 much as in colder latitudes, notwithstanding the abundant rains which 

 take place there, because the condensation occurs, and the temperature 

 is increased at a greater height in the atmosphere, and the reduction of 

 the incumbent pressure in the part is spread over a wider area. The 

 condensation takes place too at an elevation, where the air, from being 

 subjected to inferior pressure, is more attenuated, and the heating is 

 consequently more diffused. Rain is formed in certain latitudes, say at 

 an average height of 3,000 feet, where the air has a density proportioned 



