6 ÖKi>iM Lejmstöji. 



the kind influence of Senator Norrmén, I received a subvention of 2,000 

 Marks ' and with this means and tlie continued help of Governor (Jostunlier 

 I executed the experiments, wliich will be detailed here. 



In order to acquaint the reader with the signification of the niethod em- 

 ployed and its eifects, it is necessary to deal with the phenomenon in general 

 and the causes of its appearance. 



Befoi'e proceeding to treat this mattei', I will as a general rule lay down: 

 that a method to prevent the damage of frost, it may be as easy as possible 

 and as chep as can be, never discharges the agriculturist from bis duty to 

 take all the steps necessary to diminish the danger of frost on bis flelds. 

 It happens now so well that all means, spent to augment the fertility, also 

 diminish the susceptibility to frost. A well drained land acts against the frost 

 in letting the cold air scape along ditches and trenches! A fertile field will 

 produce plants, higher and stronger developed, which resist the frost far better 

 than weak and crippled ones. 



I. 



ON TUE CAUSES OF NIGHT-FROSTS IN SUMMER. 



The principal cause of night-frosts is no doiibt the radiation of heat from 

 lie surface of the earth and from the things that are upon it. [See Note I] 

 Every body, the température of which is higher than that ot its surroundings, 

 sufters a constant loss of heat until its température is the same everywhere. On 

 a summer-day the surface of the earth is lieated by the sun, i. e., the earth 

 obtains a surplus of heat, which in varions kinds of surfaces is différent and 

 which pénétrâtes more or less deeply into the ground, depending on the con- 

 ducting power of heat. When the sun's effect bas ceased, the earth and the 

 objects on it begin to give out heat through radiation in space. The tempéra- 

 ture of the eai'tli sinks at first very rapidly, being bigher in comparison to 

 that of space, but låter more slowly, depending on the circumstances of its 

 suri'oundings. The radiated heat must tirst go through the atmosphère, which 

 contains besides the principal ingrédients of air, aqueous vapour, carbonic 

 acid, small quantifies of ozon, nitric oxides, ammonia and water in solid and 

 liquid form and particles of dust of varions kinds. 



1 The Finnish mark = the franc. 



