88 



FOREST INFLUENCES. 



Tvmpi'raliire differences in yJade and plain. 



Again, J)r. Hamberg; studied tlie relations of this difference to the 

 direction of wind, and fonnd the effect to be very slight, perhaps not 

 appreciabh'. Tlie horizontal reflection of the rays of heat from tlie 

 foliage could cause an area of greater maxima and the shelter from the 

 winds an area of lower maxima about a forest. The two together 

 would cause an area of greater am])litudes or more rigorous climate, 

 and this has been directly observed by La (Jour in Denmark. Obser- 

 vations ^vel•e taken at a series of stations at dillerent distances from 

 the margin of the forest but at elevations above the sea, varying by 

 only 10 or 12 feet. The result of twenty-four days' observati(m in the 

 summer of 1807 in Jutland are given in the following table, where the 

 corrections for differences of elevation are already made. The ther- 

 mometers were arranged on a line from a northern to a. southern forest: 



station. 



200 feet witliin northern forest 



At its ni:iri;iii 



200 feet from iiiiirgiii 



401) feet f 1(1111 iiiarji'iii 



2lKI feet fioiii soutli forest 



At its iiiiirgin 



200 feet within it.' 



Daily 



aiii]ili- 



tude. 



Degrees. 

 9.2 

 9.9 

 i:t.3 

 12.6 

 13.3 

 12.4 

 11.0 



It appears that the least amplitudes are in the forest and the great- 

 est at something over 200 feet, not less than 400 feet, outside. In this 

 case the highest temi»eratures are at the same distance. A correspond- 

 ing series of observations were taken on the island of Zealand, and a 

 similar area of highest amplitudes was found. 



OONCLITSIONS REGARDING TEMPERATTTRES WITHIN AND WITHOUT 



FORESTS. 



This completes the review of tiie direct comparative observations of 

 temperatures in woods and without. While the t)bser\'atioiis show, 

 like all other meteorological i)henomena, very great variations due to 

 soil, topography, latitude, and many other agencies, they permit us to 

 draw a series of couclusitms which nnu' be considered as definitely 

 established in their general features. Tliey are — 



