MEAN TEMPERATURES IN FORESTS AND OPEN FIELDS. 



95 



be selected, otlierwise suitable' and wliere the difterences ot elevation 

 are less marked. Such are yiven in the accompanying table. One 

 station is in the wooded district, the other in the plains, and they have 

 been selected with reference to being in the same latitude, to being as 

 near the maigin as possible, and to having at the same time only mod- 

 erate ditfereuces of elevation. 



Mean IciiipcidtKri's for stationx i?i j;«ir.s. 



Littli' Kock 



Fort Sill 



Fort Siuith 



Flirt Elliott 



Davenport 



Korth Platte .... 



Moorliead 



Bismarck 



St. ViiKiait 



Fort Assinniboiiie 



Lat. N. 



34.7 

 34.7 

 35.4 

 35.5 

 41.5 

 41.1 

 46.9 

 4(5.8 

 48.9 

 48.5 



Alti- 

 tude. 



Feet. 



288 



Annual 

 mean 



temper- 

 ture. 



o 

 00.0 



.Tune temperatures. 



Mean. Max. Min 



75.3 

 73.1 

 75.0 

 82.1 

 68.4 

 75.6 

 64.5 

 67.9 

 61.4 

 69.9 



85.7 

 90.5 

 87.5 

 92.3 

 76.6 

 87.0 

 75.6 

 78.6 

 73.1 

 82.5 



67.4 

 67.8 

 65.7 

 67.7 

 58.9 

 64.9 

 52.2 

 55.6 

 48.8 

 58.4 



December terajieratures. 



Mean. Max. Min. 



43.4 

 38.2 

 39.2 

 38.1 

 26.9 

 28.1 



9.5 

 11.9 



4.0 

 21.5 



50.9 

 53. 1 

 50.8 

 52.7 

 34.9 

 42.9 

 20.1 

 26.6 

 14.7 

 32.8 



35.2 



37.1 



30.0 



28.3 



19.3 



20.8 



0.4 



6.7 



.5.8 



14.1 



The mean annual temperatures are persistently lower at that station 

 of the pair which is situated in the wooded district. The same is true 

 of the mean June temperature, while it is reversed for tlie December 

 one. The maxima are lower at the stations in the wooded area and 

 also, generally, the minima. The mean monthly amplitudes for each 

 pair for June are IS-^.a to 22^.7, 21o.8 to 24o.6, IJo.T to 22°.?, 2S°A to 

 23-3.0, 240.3 to 240.1 ; for December they are 15o.7 to I60.O, 20° 2 to 

 240.4, 150.6 to 220.1, 190.7 to 190.9, 200.5 to I80.7. They are generally 

 larger at the station on the i>lains — always so at the lower latitudes. 



It appears, therefore, that wooded districts have an advantage in 

 temperatures over treeless areas. The forests lower the mean tempera- 

 ture slightly and also cut down the range. 



There lias been much discussion over evidence of change of tempera- 

 ture at individual stations, or over more extensive areas, which might 

 accompany changes in the quantity or distribution of the forests. The 

 general opinion is that the data are not sutlicient to give satisfactory 

 cou<*lusious. To be sure of a cliange, one must be sure of a definite 

 and marked change in the amount of forests and must also be s*ire of 

 the temperatures before and after the cliange. Tlie Hrst requirement 

 is not without its difficulties, and the second is usually impo.ssible. 

 The early observations, if any were taken, aie always defective in 

 methods, instruments, and the care given to them. A variation in 

 the exposure of the tlnn-moineter alone might cause a greater difi'erence 

 of mean temperature than we would expect to find between forests and 

 prairies. 



