MR. ESPiPS PAPER READ TO THE BRITISH ASSOCIATION. 543 



and near New Haven, Ct., off the light house, Captain Woolsey, of the 

 steam boat Providence, informs me that on Sunday afternoon till near 

 sunset, the wind was strong at N. N. W. ; but at 9, P. M., it had veered 

 to N. W. and was very heavy. 



[From the Boston Mercantile Journal.] 



Mr. Editor I learn from your paper of the 14th inst., that Mr. Espy 

 stated in his late lectures, that the observations of the storm of December 

 15th, which I published, " were taken in the evening after the storm 

 had passed away ;" and that to prove any thing, these observations 

 " should have been made in the middle of the day." 



To answer this, I need only say, first, that on putting down the obser- 

 vations made at noon on that day, I find the same general result as in the 

 statements and diagram before published, viz : a circuitous course in the 

 wind which was moving around the centre of the storm : This centre, at 

 noon, being of course in a different location from that found at sunset. 



W. C. REDFIELD. 



New York, ISth Jan. 1840. 



Mr. Redfield says this storm blew in a great circuit round its central 

 portion in the direction which is contrary "to the hands of a watch which 

 lies with its face upwards, as is found to be the case in all gales which 

 he has examined, not excepting even those upon which Mr. Espy is ac- 

 customed to rely, in his attempts to sustain his favorite hypothesis of a 

 centripetal motion ! ! Let the candid reader judge who makes hypothe- 

 ses. I disclaim them. 



D. 



Mr. E spy's Paper , read at the meeting of the British Asso- 

 ciation. 



[From the London Athenaeum, Oct. 1840.] 



Mr. Espy read a paper at the meeting of the British Association, to 

 show that the four fluctuations of the barometer which occur daily, are 

 produced entirely by the increasing and diminishing elasticity of the air, 

 due to increasing and diminishing temperature. When the sun rises, 

 the air begins to expand by heat ; this expansion of the air, especially of 

 that near the surface of the earth, lifts the strata of air above, which will 

 produce a reaction, causing the barometer to rise ; and the greatest rise 

 of the barometer will take place when the increase of the heat in the 

 lower parts of the atmosphere is the most rapid, probably about nine or 

 ten, A. M. The barometer, from that time, will begin to fall ; and at the 

 moment when the air is parting with its heat as fast as it receives it, the 

 barometer will indicate the exact weight of the atmosphere. The bar- 

 ometer, however, will continue to descend on account of the diminishing 

 tension of the air, and consequent sinking upon itself, as the evening ad- 

 vances, and its greatest depression will be at the moment of the most 

 rapid acceleration of diminution of temperature, which will be about 4 or 

 5 o'clock. At this moment the barometer will indicate a less pressure 

 than the true weight of the atmosphere. The whole upper parts of the 

 atmosphere have now acquired a momentum downwards, which will 



