METEOROLOGICAL OBSERVATIONS. 



187 



to give the daily normal reading for comparison with the actual reading on that day 

 as observed. For the hours 8 A. M. and 8 P. M. this comparison is strict since the 

 diurnal fluctuation at these hours is nil ; but for the comparisons of 2 A. M. and 2 

 P. M. a new set of tables of normal temperatures wefe constructed by applying the 

 correction for maximum diurnal fluctuation at these hours to our first table of nor- 

 mals. We thus have four comparisons, at equal intervals, four observations each 

 day; these differences of temperature were tabulated and inserted in the proper 

 column for the direction of the wind then observed. There were nine such columns, 

 one for each of the eight principal directions and one for calms. The mean differ- 

 ence for each wind, for a period extending over a season, very nearly indicates the 

 elevating or depressing influence of each wind. A + sign indicates warmer, a — 

 sign colder temperature than the normal. An extension of this investigation to 

 twelve hours a day would only add to the labor without materially affecting the 

 result. By the process adopted the influence of the wind will be found independent 

 of the annual and diurnal fluctuation of temperature, and any possible tendency of 

 the wind to blow from a certain direction at the same time each day can be taken 

 into account. 



The results for the hours 2 A. M., 8 A. M., 2 P. M., and 8 P. M., do not mate- 

 rially differ; thus for the N. E. wind we flnd at these hours — 1°.9, — 2°.l, — 1°.7, 

 and — 1°.8 respectively, and for the warmer S. W. wind at the same hours, +2°. 6, 

 + 0°.5, +1°.0, and +0°.4. 



As there are but few entries of winds from the north, east, south, west, and north- 

 west, the results were contracted in two means, one for the winter half of the j^ear 

 (October to March inclusive), the other for the summer half (April to September 

 inclusive). The blanks in the table indicate too few observations to give any 

 reliable result ; numbers between brackets are of little value. 



Elevating (+) or depressicg ( — ) effect of the winds on the temperature of the air. 





K. 



N. E. 



E. 



S. E. 



S. 



s.w. 



W. 



N. W. 



Calm. 



Winter half year . 

 Summer " 

 Year . . . . 



+ 20.5 

 ^-0.2 

 + 1.3 



— 10.6 



2.2 



—1.9 



— lo.l 



+ 30.5 

 —0.3 

 + 2.4 



( + 8°.T) 



+50.1 

 —1.1 



+ L2 







30 2 



+ 3.0 

 —0.3 







(+90.8) 



(-0°.3) 



Number of entries 



36 



637 



1 



49 



1 



225 



11 



1 



3Y4 



The northeast and east winds are cold winds, the southeast, south, southwest 

 (and probably west also) are warm winds ; calms depress the temperature. The 

 northeast wind is cold all the year round, and the southwest is warm, particularly in 

 the winter ; during winter calms are accompanied by a lower temperatiu'e ; during 

 summer by a high temperature, m opposition to the winds. The distribution of 

 the winds is very irregular ; the prevailing wind, northeast, blows longer than all 

 the other winds together, in which time that of the calms may also be included. 



If we take for the effect of south and Avest winds the mean of the effect of the 

 adjacent winds, and subtract 0°.5 from all numbers, we find the values given below. 



