On Niffht-Frofttfi. 



31 



the barn. The experiments were made över an area of l,i hectare (2,7 acres), 

 ïhe field was situated on the S side of one of the trenches near the juuction 

 and below the valley which interrupted the aforesaid sand-hill; as mentioned 

 above it sloped gently towards the trenches. It consisted of 9 plots of ground 

 about 10,5 m. broad. The lines in fiehl C. dénote the ditches which, on the 

 south side, came iip to the boundar}^ of the tield. 



In this fiekl 111 torches were pretty evenly pbiced along the edges of 

 the ditches. They were lighted at 10,3o p. m. and acted very satisfactorily. 

 At the points «, h, c, rf, e, thermometers Avere placed on pôles, one being 

 near the ground and the other 1,2 m. higher up. At /' and g thermometers 

 were placed close to the ground. On the tables, the indications of the lower 

 thermometer are marked by T„ and tliose of the upper by T,,. Outside the 

 field of experiments, at a distance of 30 m., at point x, a thermometer was 

 placed on the ground, in order to observe the changes of température there. 



The foUowing table, Tab. I, shows the changes of température until 2 

 p. m., June 12'\ 



TAB. I. 



In order to illustrate the changes of température, thèse observations have 

 been given here in curves. 



' All the zero-pniiits of the thermometers had been determined and the observations corrected. 



