Effects of Radiation. 5 



ing cloud, the temperature may rise at niglit several degrees 

 above the freezing-point, and the next, the cloud having 

 passed away, the sky having become very clear, it may fall 

 as many below that point. Within a few hours, it is not 

 uncommon to experience almost every variety of weather ; 

 a frost may suddenly succeed rain, and freeze it ; the thaw- 

 ing snow be arrested, and converted into a surface of ice ; 

 thawing and freezing alternating with the passing clouds. 

 This last winter, drops of ice were several times seen hang- 

 ing from the leaves of evergreens, — frozen drops of I'ain ; and, 

 once, the leaves, after a slight rain, followed by a clear sky 

 and frost, were covered with a varnish of transparent ice, of 

 sufficient thickness to admit of separation, and when sepa- 

 rated, as it readily was, bearing not only the exact form, but 

 also a perfect impression of the leaf, as a cast, shewing 

 its most delicate fibres. Farther, in exemplification of the 

 sudden atmospheric changes to which this climate is liable, 

 I may mention a circumstance related to me by a dis- 

 tinguished individual, whose poetry has rendered this country 

 classical, and imparted to it surely an enduring interest. He 

 and his sister, in a Avinter afternoon, made a call on a family 

 in one of the adjoining valleys. The sky was obscured when 

 they entered the house ; there was a little fog, or it may 

 have been drizzling rain. Their visit was short, it might 

 have been of ten minutes ; on coming out, they found the 

 ground covered with ice, so slippery and dangerous, that they 

 considered it necessary, after going a little way, to stop at a 

 hamlet and get the village shoemaker "to sharp" their 

 shoes, that is, put nails into them, before they could venture 

 to proceed home. 



Owing to the same influence — radiation, considerable dif- 

 ferences of temperature are often perceptible here in going 

 from one spot to another, even in the course of a few minutes. 

 I may notice some instances. On the 20th of March, when 

 the atmosphei'e was very clear and calm, shortly after sun- 

 set, a thermometer in the air in a meadow, in the lower 

 part of the valley of Ambleside, stood at 20°, and placed on 

 the grass fell to 18°. Ascending immediately to a field only 

 a few minutes walk, about thirty feet higher, the thermo- 



