TOL. LXI.] 



PHILOSOPHICAL TRANSACTIONS. 



145 



XXXIII. Meteorological Observations at Caen in Normandy ; for 1765, I76d, 

 1767, 1768, 1769. By Nathaniel Pigot, Esq., F.R.S. p. 274. 



This meteorological register contains the greatest and least heights of the ba- 

 rometer and thermometer, in each month of the years above mentioned; with 

 remarks on the winds and the weather. At the end of the register, the means 

 of the heights of the barometer, ai|e qoHected, and ranged in a table, as follows : 



Mean Heights of Barometer at Caen in Normandy. 



Months. Mean Heights in Inches, in 



January 



February 



March 



April 



May 



June 



July 



August 



Sept. 



October 



Nov. 



Dec. 



Means 



17O0. 



30 35 

 3{).0(i5 

 •29 5 5 

 29.875 



296 



.9 505 

 '.J0.495 

 29.9; 6 

 29 9^0 

 30.000 

 29..^)90'29..^85 

 29.660 '30.(i6"5 

 . . . m-990 



. . . 29.555 



29.6+0 



29.730.. .. 



1766. 



1767. 1 176s. 



29.57329.550 



2^.665129.965 



|29.705 



9-795 



29.860|2976o 

 29.77029.855 

 29. 82329.840 

 .. .'30.015 

 29.890 29-740 

 29920 

 29790 

 29.8 1 5 



29.655 ':9 992 29.790 



29.+ 10 

 29-770 



29828 



1769. 



.-.. These observations were made at 

 noon, in a south-west room, with a 

 barometer, whose tube is about -^-^ of 

 an inch diameter; in which the mo- 

 tion of the quicksilver, in squalls and 

 gusts of wind, is extremely percepti- 

 ble ; yet for further satisfaction, Mr. 

 P. ordered another to be made in Lon- 

 don, with the greatest care, by Heath 

 and Wing, with a nonius giving the 

 -pfj- part of an inch. He placed this 

 barometer by the other, in July 1769; 

 and having compared them every day 

 for a year, he found that the ancient one marks t-J-j- of an inch more than the 



other ; therefore, if from th.e rnean height as above 29. 802 



be deducted. , «. 



29-825 

 29 725 

 29-8.-15 



2960, 



29 945 



29920 



29.('00 

 29 810 

 29-785 

 2y.980 

 i0 035 

 29.59" 



29.8O5 



'And the mein of all tbe!>e 5 means is 29-802. 



on 



;^F« i' * »lm*m '•''JTi^ ^t 



I <9 •' 4 • -W . 



0.050 



the true mean height is 29.752 



The greatest height observed at noon was, Jan. 29, I766 30.72 



The least, Dec. 23, 1 769 28.69 



Limits of the motion of quicksilver 2.03 



Hence it appears, that if the mean height of barometers, on a level with the 

 surface of the sea, be supposed, with Dr. Scheuchzer, Phil. Trans. N° 405, 406, 



29.993 inches 



and the mean height at Caen .... 29-752 ditto. 



then the mean difference 0.241 will be the greater mean weight of 



the atmosphere at the surface of the sea, than at Caen: and if, with the doctor 

 we allow, for each lOth of an inch depression of the quicksilver, QO feet eleva- 

 tion, Mr. P.'s room, which is in the highest part of the town, will be about 217 

 feet above the level of the sea. 



VOL. XIII. U 



