20 



RECORD AND REDUCTION 



proximate value for the diurnal change for the middle of each month, the above 

 formula was used, the increase in the value of 6 for one day being 59'.2. Multi- 

 plying the daily change into the above intervals, we obtain the following mean 

 monthly temperatures corrected for unequal duration, to which numbers the cor- 

 rection for index error has been added, as given in the third column of the table. 



Poet Kennedy. .Mean Temperature of the Air in Shade in each Normal Month. 



Month. 



January . 



February . 

 March . 



April . . 



May . . 

 June 



Mean temp. 



—35.87 



- L6.98 



— 1.68 

 4-15.87 

 4>35.67 



Corr'd for index. 



— 34°.44 

 —36.89 

 L7.44 

 — 1.98 

 4-15.87 

 4-35.67 



Mi.nth. 



Mean temp. 



Corr'd for index. 



July . . 



August 



September 



October 



November 



December . 



-39°.98 

 --36.76 

 -25.13 

 - 7.27 

 -11.43 

 -33.09 



--39°.98 



--36.76 



--25.13 



-- 7.12 



—11.86 



—33.75 



The maximum corrections for inequality in the length of the month were +0°.94, 

 in April, and — 0°.32, in October. The above monthly means, as corrected for 

 index error, will be found represented by the expression (II) — 



T= +2°.02 + 39°.20 sin (o + 249° 5') + 0°.80 sin (29 + 256° 56') + 1°.06 sin (39 4 274° 43')- 

 The numerical coefficients differ but slightly from the corresponding values in the 

 first expression. The observations are represented as follows (the hundredths have 

 been omitted as having no real value) : — 



Month. 



January 

 February 

 March 

 April 



May 



June 



Mean 

 corrected 



for index 

 error. 



— 34°.40 

 —37.08 

 — 1S>22 

 — 2.92 

 4-15.04 

 4-3J.ll 



Mean cor- 

 rected for 

 index and 

 inequality. 



— 34°.44 

 —36.89 



—17.44 

 — 1.98 

 4-15.87 

 4-35- 07 



Same bv 

 Form. II. 



— 38°.42 

 -- 33.13 

 —19.74 

 — 2.07 

 4-17.52 

 4-34.01 



Differ- 

 ence. 



4-4°.0 

 4-2.3 



4-0.1 



—1.6 

 +1.7 



Month. 



Mi- an 

 corrected 

 for index 



error. 



July 



August 



September 



October 



November 



December 



--in .12 



! 95 

 --25.43 

 -- 7.44 

 —11.60 

 —33.63 



Mean 



+ 1.85 



Mean cor- 

 rected for 

 index and 

 inequality. 



--39°.98 



--3(3.76 



--25.13 



-- 7.12 



—11.86 



—33.75 



4- 2.02 



Same bv 

 Form. II 



4-40°. 92 



4-36.81 



4-24.94 



+ 7.65 

 —13.12 

 —31.13 



4- 2.02 



Differ- 

 ence. 



— 0°.9 

 0.0 

 40.2 

 —0.5 

 41.3 

 —2.6 



0.0 



The differences between the observed and computed mean monthly temperatures 

 are greatest in winter, which is due to the greater fluctuations of the temperature 

 in that season. The same result was found from my reduction of the Van Rensse- 

 laer Harbor temperatures, as observed by Dr. Kane. The average probable error 

 of representation of the mean temperature of any one month is accordingly +2°.l, 

 and of the result for the mean annual temperature +0°.6. 



The following table contains the temperature of the several seasons at Port Ken- 

 nedy; December, January, and February being reckoned as winter months (and 

 so on for the other seasons), in accordance with meteorological usage. The results 

 by Formula II refer to the corrected normal months ; the results headed " by ob- 

 servation," are corrected for index error. 



