163 IV. CLIMATE. 



and August of other j'ears, so high a temperature as 39 

 was not indicated by mountain springs in Aberdeenshire, 

 Forfarshire, and Perthshire, except by those below 3000 

 feet of altitude. 



The temperatures of twenty -three springs on the 

 Grampian mountains, about latitude 47, in the East 

 Highlands, were noted down in July and August of 1841 

 and 1844. The discrepancies between these were so 

 considerable, as to render an average deduced from the 

 whole far from satisfactory ; although it may be the best 

 yet attainable. The temperature of the highest of these 

 springs was 37, at the altitude of 3450 feet in Aberdeen- 

 shire, on July 12, 1844. On comparing twenty-one 

 others, each one in succession with this highest spring, 

 their average rise of temperature is found to be at the 

 rate of one degree of Fahrenheit for 32S feet of descent. 

 In making this average the note for one of the springs is 

 rejected, on the supposition of some error; as it indicates 

 only half a degree of the thermometer for a difference of 

 700 feet in altitude. 



Extreme exactness cannot be attained ; and while this 

 is the case, it may be well to adopt some rule which will 

 adapt itself to our instruments, and can be readily ap- 

 plied to botanical objects. On the figures above given, 

 there can be no wide error in assuming the relation of 

 temperature and altitude to be at the rate of one degree 

 for one hundred yards ; that is, a decrease of temperature 

 at the rate of one degree of Fahrenheit's scale for each 

 hundred yards of ascent. This rate may likely be some- 

 what too rapid for the temperature of the ground, as 

 measured by that of springs. On the contrary, it may 

 perhaps be rather too slow for the decreasing temperature 

 of the air, not close to the surface of the ground. The 

 growth of mountain plants, seldom rising many inches 



