852 



The Meteorology of TFhitehaven. 

 Terrestrial Radiation. 



The direct eiFect of terrestrial radiant heat is determined by exposing 

 a delicate naked thermometer on a grass-plot, and comparing its mini- 

 mum with that of a Six's thermometer at four feet above the ground. 

 The difference is the amount or effect of the radiation. 



The first part of the above table needs no explanation. The first 

 column under the head ** Radiation," shews the greatest difference be- 

 tween the minima of the naked and standard thermometer, under the con- 

 ditions above described ; the second column indicates the day of the 

 month on which it occurred ; the next gives the least difference during 

 the month ; and the last exhibits the mean radiation, or sum of all the 

 nightly differences during the month, divided by their number. Thus, 

 the naked thermometer in 1846, one night with another throughout the 

 year, has fallen 1^ degrees lower than the standard thermometer at four 

 feet. 



The naked thermometer is generally exposed on a flat piece of cork 

 about an inch in thickness, but in clear and settled weather it is placed 

 in a wicker^ basket containing a layer of raw wool. Under a clear sky, 

 the difference between a thermometer on cork and one on wool, is about 

 2°-3 in favour of the latter ; but in cloudy and windy weather, the indi- 

 cations of both are very nearly the same. 



The naked thermometer has been below 32° in every month of 1846, 

 except June and August. In June it fell to within l-°5, and in August to 

 within 5° of the freezing point. 



