Sir D. Brewster on certain Isothermal Lines in Ameiica. 431 



Table III. — Showing the State of the Winds observed thrice a 



day. 



During the past year there were, 



92 North winds 

 49 NNW 

 59 NW 

 32 WNW 



85 West 1 170 South 



45 WSW 34 SSE 



106 SW 49 SE 



41 SSW i5 ESE 



23 East 

 6 ENE 



42 NE 



21 NNE. 



Hence we see that the prevailing winds are those of the 

 south and the south-'west. 



LXXVI. Observations on the Isothermal Lines on the North- 

 west Coast of America, as deduced from the Results in the 

 two preceding Articles. Bij Sir David Brewster, LL.D. 

 F.RS. Ssc. 

 TN determining die inflexions of the isothermal lines round 

 *- the pole of maximum cold in the Arctic regions to the 

 North of America, I employed the valuable observations of 

 Mr Scoresby; a long and valuable series of observations made 

 on the west coast of Greenland, and communicated tome by Sir 

 Charles Giesecke ; together with observations made in Iceland, 

 and in different parts of Canada. I sought in vain, however, 

 for measures of mean temperatures in those parts of the Arctic 

 regions which are placed in a meridian nearly opposite to 

 our own; and it Is therefore a source of great satisfaction to 

 me to have received from M. Kupffer the valuable observations 

 contained in the two preceding papers. These observations 

 intieed have been yet made for too short a peiiod to give us 

 a very accurate measure of mean temperature; but the ap- 

 proximate results which they afford will be of some use, till 

 we obtain a larger series. 



In order to compare the observed mean temperatures of 

 Jloidouk and Sitka with those calculated from the formula 



Mean temperatme = (86°-3 sin D) —3^, 



D being the distance of the place of observation from the 

 North American pole of maximuui cold, which is situated in 

 north latitude 80", and west longitude 100°. 



Professor Kupfler has not given us the longitude and lati- 

 tude of Jloulouk and Sitka. The position of Ounalachka, 

 however, according to the observations of English naviga- 

 tors, is between 1(J8"' 40' and 1C8° of west longitude, and be- 

 tween 53° 45' and 54° of north latitude. We shall take, there- 



