THE ENGLISH LAKE DISTRICT. 115 



the 20th and 30th January, 1848, the ice had parted with 0-324 inch, or -032 per 

 diem, the average daily loss for the month being only -024 inch. For five days of 

 December, 1848, the loss was -037 per diem, the daily average for the month being 

 .032 ; and, from the 1st to the 8th of January, 1849, the depth evaporated was 

 equivalent to -017 per diem, the average daily loss during the month being 029 

 inch. Lastly, in the first six days of January, 1 854, the loss from the frozen con- 

 tents of the gauge was 0*2] 9 inch, or -036 per diem, which is identical with the 

 average daily evaporation in that month. Hence it appears that, notwithstanding 

 the large amount of heat required not only to liquefy but to vaporize frozen water, 

 the vapour thrown off by ice in an invisible form exceeds in amount the average 

 daily evaporation from an equal surface of water, in the winter season. This 

 apparently anomalous circumstance arises from the extreme dryness of the atmo- 

 sphere, and its consequently increased capacity for vapour, in severe frosts; 

 whereas, at other times during the winter, the air is very moist near the sea, 

 being generally not more than 2° or 3° above the point of saturation. 



At Whitehaven, the average amount of Evaporation for the twelve years end- 

 ing with 1853, is 29-664 inches, and the fall of rain for the same period is 43 # 02 

 inches,* so that the depth of water precipitated exceeds that taken up by evapo- 

 ration at the coast, in latitude 54 o, 30, by 13-357 inches. In the almost tropically 

 fine and dry year 1842, the evaporation (36-83 inches) exceeded the rain-fall by 

 2-143 inches. The evaporation is not unfrequently in excess in the months of 

 March, April, May, and September ; and, in 1 853, the amount of vapour absorbed 

 by the atmosphere equalled or exceeded that which was restored to the ground 

 in a liquid form, in seven months of the year. 



The evaporation force at the altitudes of our highest mountains appears to be 

 very feeble, notwithstanding the greatly diminished pressure of the air. At the 

 summit of Great Gabel, (2925 feet above the sea) there is a vertical cavity in the 

 rock, which, owing to the almost continuous presence of clouds, the high degree of 

 humidity, and consequent slight evaporation at this elevation, always contains 

 water, except in the very driest seasons. It is commonly believed that this " at- 

 mospheric spring" or well, as it is called, is never empty. The traditionary belief 

 is, however, not strictly correct. The well was quite dry in the Spring of 1844, 

 and also in April, 1852. 



The Evaporation Gauge is a copper vessel, 8 inches in diameter, and rather 

 more than an inch and a half in depth. Half an inch of water is accurately mea- 

 sured and poured into the dish every morning at 9 o'clock, and the loss is ascer- 

 tained at the end of 24 hours by means of a carefully-graduated tube, reading to 

 the logoth part of an inch. 



The evaporation dish receives a fair proportion of wind and sun, and is 

 always exposed in the open air during the day, except when rain is falling. At 



* The average annual rain-fall for 20 years, at Whitehaven, is 46-59 inches. 



