1^22.^ Col. Beaufoi/'s Meteorological Journal for 1821 . 91 



with the daily mean ; and in almost every other case, there is a 

 greater probability that this mean should be accurate than that 

 the one found from two, three, or even a greater number of 

 observations should be so. It seems then that the self-register- 

 ing barometer affords a much more certain method of obtaining 

 correct results of the daily pressure of the atmosphere than any 

 other that could be conveniently adopted ; but as the foregoing 

 observations and remarks may not appear so conclusive to others 

 as they do to myself, 1 purpose giving a series of observations 

 made with the common and self-registering barometers in the 

 month of October, which, I trust, will prove to the satisfaction 

 of every one the great superiority of the latter as a meteorological 

 instrument. 



Article III. 



Meteorological Journal kept at Bushey Heath, in the Year 1821. 

 By Col. Beaufoy, FRS. 



(To the Editor of the Annals of Philosophy,) 



DEAR SIR, Bufhey HeaHi, Stanmore, Jan, 7, 1822. 



You will oblige me by inserting in the Annals of Philosophy o. 

 summary of a meteorological table kept by me at this place, 

 and which I beheve to be accurate ; one day's observation only 

 (the 17th of July; is omitted. The mean monthly heights of the 

 barometer, thermometer, De Luc's hygrometer, together with the 

 quantity of rain and evaporation in inches, are inserted, as well 

 as the mean temperature observed with a Six's thermometer. 

 The altitudes of the barometer and thermometer were taken at 

 nine o'clock in the morning, at which hour the heat of the 

 weather nearly corresponds with the mean temperature of the 

 natural day ; the greatest difference in January amounting to 

 2*83 degrees, the thermometer in the morning being minus that 

 quantity. The rain guage is I64. feet above the ground, and 

 538^- feet above the sea. This height was deduced from several 

 corresponding barometrical observations made at Bushey, and 

 in the Strand by Mr. Gary, whose instrument is 73 feet higher 

 than the mean level of the sea; and the summit of Bushey 

 Heath 558 feet, or four feet lower than the Signal House at 

 Beachy Head, which I found was elevated 562 feet above low 

 water mark. 



On the 25th of last month (December) at half-past twelve in 

 the morning, the mercury in the barometer at this place sunk to 

 27*609 inches, the night was very dark, with fog and small rain, 

 accompanied by a light wind from the eastward. This unusual 

 dcpressioa of the quicksilver, instead of being indicative of a 



