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XV. — On the Action of the Atmosphere upon iieioly -deepened Soil. 

 By Thomas F. Jamieson, Ellon, Aberdeenshire. 



Prize Essay. 



Soil or earth newly turned up to the surface is exposed to many 

 influences which before affected it either not at all or only in a 

 faint degree. These influences mainly arise from the atmos- 

 pheric envelope surrounding our planet, and from the rays of 

 that luminary whose powerful attraction guides it in its path 

 through space. 



But besides this exposure, the soil is also thus released from 

 pressure, and has full freedom to expand, crumble down, and 

 spread itself out to the enriching effects of the sun and air, 

 and to inhale freely the breezes which play around it, bringing 

 materials which are as necessary for its amelioration and changes 

 as tliey are to the living organisms that exist upon its surface. 



The subject, therefore, naturally divides itself into these two 

 branches : — 



1. The sola?' influences, embracing the effects of temperature 

 and light. 



2. Tlie aerial influences, or those arising from that mixture of 

 substances which forms our atmosphere. 



It is proposed, therefore, first to take into consideration the 

 action of the sun's rays, then to pass on to the effects produced by 

 the several constituents of the atmosphere, and after that to look 

 somewhat into the ingredients of tlie soil with the view of 

 showing how they are likely to be affected by tliose agencies 

 which will have come under our notice. In this manner, it is 

 conceived, opportunities will be afforded of touching upon all 

 those topics which this paper should embrace. 



First, then, as to tlie influences emanating fi'om the sun. 

 The sunbeams which play upon our globe liavc a more compli- 

 cated action than was of old supposed. Newton, transmitting 

 one of these beams through a glass prism, found the resulting 

 spectrum to be composed of the seven rays, red, orange, yellow, 

 green, blue, indigo, and violet ; which Brewster would simplify 

 into tliree, Red, Yellow, and Blue, and their modifications. At- 

 tention being tlius direc ted to the compound nature of the solar 

 radiations, it was soon observed that tliey possessed different 

 properties, and it is now found that they have at least four well- 

 marked characteristics : — 



1. The calorific, or jiower of imparling heat. 



2. The luminous, or j)ow('r oi inij)arting light. 



3. Tlic chemical, or power of inducing chemical changes. 



