32 



BUI4LETTN 1233, V. S. DEPABTMENT OF AGRICULTURE. 



and again an unseasonable rise with the recurring winds of March. 

 April brings much less wind and the heaviest snows; hence the low 

 temperatures. 



(5) The autumn temperatures contain little of interest unless it 

 be in the somewhat sharp depressions for the second decade of Sep- 

 tember and the second of October, which are very often periods of 

 heavy, wet snows. 



Range of air temperatures. — It is very doubtful whether the range 

 of air temperatures is of much biological significance, at least in con- 

 nection with plants so " hardy " and so accustomed to a great variety 

 of conditions as the coniferous trees. For this reason it seems neces- 

 sary only to show the normal values, by decades, as computed up to 

 March. 1918. . (Table 3). These have a value also in connection with 

 the table of mean temperatures in indicating the maxima and minima, 

 which may be directly computed by use of the two tables and which, 

 therefore, will be omitted. 



Table 3 shows that the mean daily range at the control station is 

 22.3°; and, although it varies for individual decades by as much as 

 7° and is greatly influenced by cloudiness, wind, and other circum- 

 stances, the maxima and minima, respectively, may be approximated 

 if 11° are added to or subtracted from the mean temperature for any 

 period. 



Table 3. — Mean daily range of air temperatures at the control sta!io?i (averages to 



March, 10 IS). 





Record by decades and months in degrees Fahrenheit. 



3 



3 



D 

 c 

 a3 



a 



cj 



M 



a 

 "i 



Decade 



a 



«-. 



03 



s 



,0 



p 



i 



a 



3 



P. 



< 



1 



| 



>> 



^5 



+3 



3 



I 



S3 



£1 



I 



<D 









 O 



- 

 fit 

 5 

 



5 



y 



! 



m 



a 



] 



22. 5 

 21. 2 

 22. 2 



24.4 

 22.0 

 19.8 



21.9 



23. 2 

 22.0 



20.9 

 19. 6 

 2a 1 



2 1 . 2 

 20. 8 



23. 6 



21. 8 

 20.9 



23. 1 

 21. 1 

 22.1 



23. i 

 22.2 



23. 2 



23.0 

 23.5 



23.0 22x3 







2 



22. 6 



23. 1 







3 

















90 



22. 2 



22. 3 



20.3 



21.3 







- 



22.7 



23. 2 







22, 32 











1 Sec note, p. 29. 



From the purely meteorological standpoint, the shortening of the 

 daily range in the stormy period of April is of some interest. Of even 

 ater interest is the de< ewindy winter months, which 



does not show up in the means because here the action and reaction 

 are about equal. A west wind may have any one of several effects 

 on the temperature curve, but uearly always gives it an abnormal 

 shape, because the wind rarely attains its greatest, force during tiie 

 warmer part of the day. Arising in the evening, after a cloudy day, 

 it may bring the maximum temperature at midnight. If the follow- 

 ing day witnesses a dying of the wind, its maximum temperature may 

 be recorded at the begini minimum at the end of the mid- 



night to midnight period. A steady wind may hold the daily range 

 down to 8 or 10 \ but a sudden rise or cessation will elevate it to 40 . 

 There are, of course, other cosmic conditions at the source of such 

 winds, which accentuate their effect on temperature. 



