47 



HOL'RLY OBSERVATIONS. 



Hourly oliserv;itii)Us wei'O maintiiiiieil dm-iiig the moatlis of ilarch, June, 

 September ami December. The entire series of observations is not here repro- 

 (hiceil as the principal object was to ascertain tlie dinruiil lluctuations. In tables 

 T and U will be Ibund the liourly means obtained for this purpose. Table T 

 contains the hourly means lor each month and table U the mears fctr the whole 

 jieriod of four months. In this the velocity of the wind is omitted and the 

 mean force of vtipor for each hour in the day is inserted. Diurnal fluctuations 

 are seen much more rjadily in charts 18, 19, 20, 21 and 22. On the two pii^es 

 of chart number IS are the barometric curves for each of the four mouths and 

 also for tlie mean of all. Concerning the curve lor the month of June and also 

 for the table for the same month, it ought to be said th;it it wis found necessary 

 to reject the observations of one day. During a portion of the forenoon of June 

 Ttli the barometer readings were undoiditedly serions'y in error an 1, as no 

 means existed fur their correction, it was consiilered best to le ejt them ciitiivly 

 and in consequence, the barometric observations for the entire <lay. The hourly 

 means of the barometer for that month are, tlierefore, based on observations 

 during 29 days instead of .30. There were no reasons for doubting the observa- 

 tions of temi)er iture, humidity etc. made n|ion the same day and they have 

 accordiuirlv been retained. The baronietric curves for the four months agree 

 |)rctty well as to their ma.xiinum and minimum paints. It is noliccalde, how- 

 ever, that the greatest maximum appears to occur about an hour earlier in Jimo 

 and December than in March and Septemlwr. There apjiears to be considerable 

 variatifin in the time of the great minimum whirh occurs in the afternoon. In 

 .lune this secn)s to be between 4 oelock and .^ o'cloclc while in December it is 

 IIS early as 2 o'clmk. In a singe series ot' hourly observations, however, the 

 results must be largely influenced by temjiorary non-periodic barometric changes 

 which sometimes are very consider ible an 1 their elYect can only be eliminated 

 by greatly mtdliplying the number of observations. As it was not p,»sible to 

 maintain hourly observations throughout the whole year, the months u( Mareii, 

 June, S«.'ptendjer and Decemlier were selected on account of the relation which 

 tiiey sustain to ihe position of tlie si n. An crimination of the curve e.Khibiling 

 the monthly means from the regular series will show tliat, in general, these 

 nionlhs were months of low b.iroinetric height and the sunc thin'' is shown in 

 the Ci>rres|K>nding emve in the report of last year. During the year IHSl a scries 

 of hourly ob.^ervations will be eanied on during those months which seem to bj 

 clmnictcrized by a liigli barometer ami these results may, in the future, l)c com- 

 bined with ihn«' furni-<hed with Ibis n-p nl. 



'J'lie amount of thi' diurnal movement for e uli ni'iiilh is ils foliowr; 



