90 



FOREST INFLUENCES. 



is the case of the temperatures in open fields about Vienna and in the 

 Vienna forest. The elevations vary by less than 200 feet and the ob- 

 servations are corrected for the variation. Tho uiean temperatures 

 about Vienna are obtained from four stations. 



The best forest station for the comparison is Hadersdorf, IS miles 

 southwest of the Hohe Warte, and its altitude differs from this by 92 

 feet. If the second or cooler pair of stations in open country near 

 Vienna be represented by A, the first or cooler by B, and the observa- 

 tions at Hadersdorf by C, the comj)arison stands as in the following 

 table. 



This table shows that there is an appreciable cooliug- in the Vienna 

 forest and that this is greatest in summer and least in winter. The 

 forest consists of beech trees only. 



A detailed comjiarison also brings out a curious fact. The tempera- 

 ture in the forest region is nearer that in the open region at the 2 p. ra. 

 observations than for that at the 9 p. m. observations. The monthly 

 means for the years 1875-1884 give the Hadersdorf temperature as 0o.2 

 higher to 0^.7 lower than the Hohe Warte temperature at 9 p.m., 1^.1 

 lower to 40.5 lower, the difference being greatest in the summer months. 

 The 7 a. in. observations are intermediate, varjdng from l^.l to 2o.2'lower 

 at Hadersdorf. The explanation of this is probably to be found in the 

 fact that the station at Hadersdorf is, in some sort, a glade station. 

 The thermometer is not under trees, but is on the north side of a build- 

 ing nnder the usual Austrian shelter. As ah-eady pointed out, the 

 glade has a greater range than the open field, and its maxima and min- 

 ima must fall at about the same hour of the day. If the 2 p. m, obser- 

 vations were deferred an hour or two, the temperatures at Hadersdorf 

 would probably be higher than at Hohe Warte. 



The stations in forest regions used in making these general compar- 

 isons are not likely to be under trees. They are the ordinary meteoro- 

 logical stations, and while in wooded territories, they could not prop- 

 erly be established under the shelter of the compact foliage of a forest. 



