VOL. LXXI.] PHILOSOPHICAL TRANSACTIONS. 1 2Q 



XXVL Further Experiments on Cold, made at the Macfarlane Observatory 

 belonging to Glasgow College. By Patrick Wilson, M. A. p. 386. 



Monday morning, Jan 22, 1781. 



Some days of very cold weather, lately in this fa Therm. Therm, 



country, afforded an opportunity of prose- y ' . . in t'. . . '-T^' 



cuting a little further the experiments and i 30..!! !!!! +2.1 ."..! -12 



observations begun in the course of last year. 1 * 5 - _» -8 



The frost set in on Sunday the 2 1 st of Jan. 3 -0. ...!!- 4 



after a considerable fall of snow on the pre- ^ 45 ~° -8 



ceding evening, and about midnight the ther- 4 30. 1 . . . ! ! 1 -3. ! . 1 11- 8 



mometers were exposed near the observatory in ^ ^ -2 -»2 



the situations mentioned in my former letter. 6 45 .' .' .' \ .'.'!! —2. .!!!.- 10 



The annexed register shows the difference of 7 -3 - 13 



temperature between the snow and the air, till 8 \ \ \ \ \ ' \ \ _ 4 [ ' ' " " _ u 



8 o'clock on Monday morning, to which are 8 30 -2 -10 



subjoined some facts which prove very consonant to those described in the former 

 paper. The sign — prefixed, denotes degrees below O. The sign + degrees 

 above O, of Fahrenheit's thermometer. 



From 1 o'clock till 3 in the morning, the thermometer in air, at the 

 balustrade of the east wing of the observatory, pointed from + 4 to -f 6, and 

 on the snow there from — 1 to 0. At half an hour after I the thermometer in 

 air, 24 feet from the ground, and to the windward of the house, pointed to 

 -j- 7, and at 8 o'clock to + 1. At 3 o'clock the snow in the park, 3 inches 

 below the surface, raised the thermometer to -f 14, and at 6 inches below, near 

 the ground, to + 24. The barometer stood at 29.8 inches, and there was a 

 perceptible motion of the air from the east and J point south. This night was a 

 very general and lively aurora borealis, most part of it of a bright red, which 

 formed a crown near the zenith; Monday evening. Therm. Therm, 



but it mostly vanished about 3 h - m - in air. in snow, 



o'clock, after which time the air 8 3o!!!!.'.'.!!!!l!J!!!l!! +14 +3 



became more still. During the 9 + 8 +1 



whole of this night, as well as l0 "!!!!!!!! !*! .' \\\\ .* .' .' J 7 \\ 



of the succeeding times of ob- ' 30 ........+ 6 + 



. , 11 Ball of therm. ', an inch 

 serving, the air was not nearly above the surf, of the sn. + 5 +3 



so much disposed to give out W Ditto + 5 +3 



'. . luesday morning, 



hoar-frost as it was last year. l Ball oftherm. as formerly 



On Monday evening the dif- half immersed in the sn.+ 6 +3 



J e , 2 + 8 -1-5 



terenceot temperature was found 2 30 +]0 _rg 



to be as in the annexed register. 



vol. xv. S 



