666 ZONES AND REGIONS [Pt. Ill, Sect. Ill 



covering, for example, over a stone has reached a certain maximum of thickness, 

 which however cannot be very considerable, melting from below commences and 

 leads to the formation of a hollow space between the stone and the snow. ... In 

 spite of the extremely slight diathermancy of snow, the sole possible explanation ot 

 the phenomenon seems to be the heating of the stone buried under the ice by means 

 of absorbed rays. It is quite analogous with the formation of prismatic cavities in 

 ice caused by substances enclosed in glaciers, and is due to the same cause. A con- 

 dition demanded before this phenomenon can definitely set in, is the previous more 

 or less complete conversion of the snow into neve . . . since neve, possessing as it 

 does physical properties between snow and ice, presumably has a higher diatherm- 

 ancy than snow. 



' I found direct confirmation of these suggestions in the following observation. At 

 noon on the nth of May, a sunny warm day, a fringe of ice, 2-3 cm. in thickness and 

 lying at the edge of a heap of snow situated on a gently inclined southern mountain 

 slope, was perforated, and a thermometer inserted through the narrow orifice, so 

 that its bulb rested on the substratum, consisting of a felted mass of Empetrum, 

 Vaccinium, and Cladina. The lateral intrusion of warm air was hindered as much 

 as possible by interposing pieces of ice ; the distance of the thermometer bulb from 

 the lower surface of the ice was only about 2 cm. Although the cold melted snow 

 could not entirely be prevented from sliding down the thermometer-tube, yet the 

 temperature remained for a long time at 7 C. As soon as the icy shell had been 

 covered by an equal thickness of snow, the temperature sank to 3 , later on to i° C. 

 Close by, on soil free from snow, a thermometer with its bulb inserted among the 

 twigs and protected against direct insolation showed 20 C. The temperature of the 

 air, measured in the usual way, was at the same time y° C 



Such favourable soil-temperatures due to direct insolation last but a 

 short time, as the clouds, and specially the frequent fogs, soon conceal the 

 sun again. They are also limited to a superficial layer of slight thickness, 

 beyond which, either somewhat deeper or somewhat less deep, according to 

 the horizontal or inclined lay of the ground, constant zero is reached. 



Middendorff * says : — 



' On soil under direct insolation I repeatedly saw the thermometer at the begin- 

 ning of August stand over 24 R., so that it may easily become three times as high as 

 the temperature of the air. From the surface downwards the temperature diminishes 

 so rapidly, that at a depth of 2 inches it is hardly half as warm, at a depth of 4 inches 

 again only half, about 3 R., whilst at a depth of 1 to i| inches the ground remains 

 frozen hard and close to it the thermometer stands at freezing-point.' 



The atmospheric precipitations' 1 during the vegetative season are small but 

 very frequent. The frequent wet fogs must be highly important to the 

 vegetation, which consists only of shallow-rooted plants. Thus Martins 

 says 3 of Spitzbergen : ' The fogs are nearly continuous and so dense that 



1 Middendorff, op. cit., p. 666. 2 See the climatic tables. 



3 Martins, op. cit., p. 73. 



