19 



<lue ^N^orth and South, skirting the seaboard of Xorway, througli 

 •Germany to Venice, where it turns East across what used to be 

 Turkey, and the Black Sea.* 



This extreme irregularity calls for some explanation. Why is 

 it, we may ask, that places so differently affected by the sun should 

 liave the same temperature 1 The answer depends very much on 

 the special conditions of each place. One, the most familiar to 

 every one, is the aspect. A place fronting towards the noon-day 

 sun, on the side of a slope, sheltered from cold winds by a line of 

 hills or high land, or even a clump of trees, is often found to be 

 very much warmer tlian other places in the same neighbourhood. 

 Most of the health resorts along our South Coast — Ventnor for 

 instance — are so situated ; so are the favourite sites along the Eiviera. 

 The giving out of heat by freezing water, or the absorption of heat 

 by melting ice, when these processes of nature go on a large scale, 

 as within the Arctic circle, have a very remarkable effect in 

 nmeliorating or embittering the climate of special localities, where 

 ice is formed and drifted away, or where ice is continually pushed 

 in and stored up to be melted. More generally important are 

 differences of soil or geological conformation. Everj'one knows 

 that on a hot July day, a green field may be pleasant enough to 

 walk in, whilst a dusty white road is almost unendurable. It is 

 that the heat, as it strikes the arid road, is at once given off to the 

 air; Avhen it strikes on grass, it remains there to do work, and is 

 -{vbsorbed in the life it nourishes. And so on a large scale, a 

 tract of country such as the Great Sahara, or the Stony Desert of 

 Australia, is as a dry dusty road of great magnitude ; the un- 

 pleasantnesses of it are magnified, and the temperature of the super- 

 incumbent air is often very great : in each of tlie above-named 

 localities, a temperature of about 1.30° F. in the shade has been 

 observed. 



But all these purely local causes, however important, are 

 trifling in their effects in comparison with those of the wind, and 

 its great ally, the ocean. The air is the receiver and transmitter 

 of all the heat which makes the earth habitable ; without the air 



* Tlie Isothermal Maps exhibited were, in the main, reproduced from 

 Mr. Scott's Ehnuntary Meteordo'ji). 



