On Night- Frosts. 43 



From this follows without cloubt that the purpose of the torches is only 

 to defer the fulling of the température, to a certain number of degrees ( 2" 

 near the gronnd) until an honr after niidnight, during the nioiitlis of efune and 

 July. The torches, liaving proved, according to the experiments, not only to 

 answer their purpose hut also to prevent the formation of hoar-frost, we seem 

 entitled to drawing such conclusions respecting the numlier of torches in 

 proportion to the area, their placing on the tield, the time of lighting etc, 

 as will be of importance for a successful result of further experiments. 



Before proceeding to the discussion of these experiments and the drawing 

 of conclusions, we will give an acx'ount of the observations made during the 

 autumn 1892, as they are of great importance for the tinal result as to the 

 use of the torches at a time of early spring-frosts or of autumn-frosts during 

 the second half of August or first half of September. 



VI. 



EXAMINATIONS OF THE RADIATION OF HEAT lUlRING CLEAR 

 NIGHT8 OF THE SUMMER AND AUTUMN OF 1892. 



The following observations, the parpose of which was a doser knowledge 

 of the dependence of température on the appearance of the sky during cold 

 summer, and autumn-nights, especially with regard to the night-frost, were 

 made at the estate of Nieniis, in the Houth of Finland. The main-building of 

 the estate is situated about 10 m above the surface of lake Wanjärvi on a 

 slope, the greater part of which is occupied by the aforesaid lake, bordering, 

 for the most part, on meadows, hut also on cultivated ground. On the N of 

 the lake there is Wanjärvi estate, with extensive lands and to the W there is a 

 village or two with their tields. In the lake flows the river Wanjoki Co- 

 ming from NNW through a valley and continuing its course SW to lake 

 Hiidenvesi. 



At Wanjärvi night-frosts are a common occurrence on the N of the lake, 

 but are very scarce on the S at Niemis, so the place was not favourable for 

 the intended examination. The rainy summer with very few clear days was 

 not suitable, either, for such investigations. They were not commenced until the 

 beginning of August and the observations were made only during clear nights. 



