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[^»j </w " Canadian Jowml,] 
 
 t-h 
 
 f I' 
 
 U- 
 
 'f^ 
 
 ON THE DIURNAL AND ANNUAL 
 
 VARIATIONS OF TEMPERATURE 
 
 AT HALIFAX, NOVA SCOTIA. , ,.,- ..^.v,. 
 
 g! Tf^INGSTON, M.A., WCv , \^ 
 
 BT 
 
 II 
 
 Director of the Magnetk Observatory, Toronto, 
 
 From Bi-Hoi'blt Observations by F. ALLISON, M.A.. Di-nisn thr THnp.E Yiam 186r-6». 
 
 For developing the climatology of this country, two or more chief 
 stations in each province are needed, differing from ordinary stations, 
 partly in the extent of their instrumental appliances, and partly in the 
 frequency of the observations. 
 
 One of the leading objects of these chief stations has been carried 
 out by Mr. Allison, of Halifax, by making the observations from which 
 the results given in this paper are derived. The nature and purpose 
 of these results will be understood from the following considerations. 
 
 The majority of observers, being engaged in their various callings, 
 cannot usually observe often enough in the day, nor persevere for a 
 sufficient number of years for the collection of materials adequate for 
 the calculation of the normal values of the elements proper to their 
 several stations. 
 
 Their observations can however to a great extent be made compar- 
 able with those carried on more frequently, and extended through a 
 lonf term of years, by applying corrections deduced from the observa- 
 tions made at a few well equipped chief stations and continued through 
 a long series of years, during a portion of which the observations have 
 been taken at equal intervals not exceeding three hours. 
 
 The corrections are of two kinds. First, the corrections by which 
 compensation is made for the insufficient frequency of the observations 
 ai: ordinary stations; and, secondly, those which compensate their 
 
 "7' . , 
 
 J o^^jO'^-'^o , 
 
 ^. 
 
(^ 
 
 
 2 ON THE DIURNAL AND ANNUAL VARIATIONS OF 
 
 insufficient continuance. It is with tlio former class of corrections that 
 this article is concerned. 
 
 Mr. Allison lias furwardod to Toronto for reduction a scries of ther- 
 mouietric readings, made by hiiu or under his direction at every even 
 hour (with a very few exccplions) durinjj; the three years 1867-69. 
 
 In a few instances, when rcadinfrs at 2 a.ui. and 4 a.m. were not 
 talccn, the ob.servation.s of the whole day were set aside. As these, 
 invludimj Sunda^n, were only 22, the unbroken days in the three years 
 amounted to 1,074, and the readings employed in the calculation 
 12,888; giving, for each month, 80 or 90 readings for each of the 
 twelve bi-hourly means. 
 
 The primary object of the computation being to learn for each 
 month the quantity by which the temperature at each hour differs 
 from the mean temperature of the month for all hours collectively, 
 interpolating formulae for each month have been constructed, by aid of 
 which the most probable temperature could be computed for any 
 instant in the twenty-four hours. 
 
 The following is the general type of the formulre.where T„ represents 
 the required temperature at any time (n) reckoned from midnight, the 
 unit of time being one hour, <„, t,, t^, &c., certain constant tempera- 
 tures, and c^, Cj, &c., certain constant angles derived from the twelve 
 bi-hourly mean temperatures for the particular month under consi- 
 deration 
 
 ^n = 'o + 'i ^in («X le + i-,) + t„ sin (2 n X IB -f c,,) + <, sin (8»iX 15 + e,) 
 
 + <j sin (4 n X 15-f c^) + t^ sin (6 n X 16 -f c^) -f <^ sin (6 « X 16 + c„) 
 
 The values of the constants t^, <,, &c., c,, c,, &c., are given for each 
 month in the following table. 
 
 TABLE I. 
 
 
 Jan. 
 
 Fm. 
 
 JUn. !Armi.[ Mat. 
 
 Jdsb. 
 
 JBI.T. 
 
 Acq. 
 
 Stpr. 
 
 Oct. 
 
 NT. 
 
 DiO. 
 
 
 
 19. S3 
 
 23.18 
 
 27.13 |37 20 
 
 48.16 
 
 6§.62 
 
 64.35 
 
 64.13 
 
 68.19 
 
 46.01 
 
 30.02 
 
 25.21 
 
 1 
 
 3.3S 
 
 4.55 
 
 6.11 I 0.80 
 
 7.81 
 
 8.42 
 
 8.04 
 
 8.18 
 
 6.87 
 
 5.68 
 
 2.77 
 
 2.64 
 
 a 
 
 1.3;; 
 
 1.37 
 
 1.72 i 1.36 
 
 1.13 
 
 0.60 
 
 0.99 
 
 1.35 
 
 1.81 
 
 1.78 
 
 1.26 
 
 1.08 
 
 3 
 
 0.32 
 
 0.26 
 
 0.12 
 
 0.36 
 
 0.00 
 
 0-78 
 
 0.78 
 
 0.74 
 
 0.42 
 
 0.07 
 
 0.20 
 
 0.33 
 
 4 
 
 0.15 
 
 0.16 
 
 0.23 
 
 0.02 
 
 0.17 
 
 0.39 
 
 0.21 
 
 0.21 
 
 0.28 
 
 0.22 
 
 0.04 
 
 0.08 
 
 6 
 
 0.15 
 
 0.13 
 
 O.ll 
 
 0.14 
 
 0.21 
 
 0.07 
 
 0.10 
 
 0.13 
 
 0.14 
 
 0.30 
 
 0.17 
 
 COT 
 
 *« 
 
 0.02 
 
 0.02 
 
 0.08 
 
 0.02 
 
 0.03 
 
 O.OC 
 
 0.06 
 
 0.01 
 
 0.10 
 
 0.03 
 
 0.02 
 
 o.oe 
 
 k 
 
 -I \, 
 
>r,T. 
 
 Dm. 
 
 .02 
 
 25.21 
 
 .77 
 
 2.64 
 
 .26 
 
 1.08 
 
 .20 
 
 0.36 
 
 .04 
 
 0.08 
 
 .17 
 
 0.07 
 
 .02 
 
 0.04 
 
 
 X 
 
 ? 
 
 »-i \.- 
 
 "•^ fe^- 
 
 TEMPERATURE AT HALIFAX, NOVA HCOTIA. 
 TABLE 1.— {Continued.) 
 
 $ 
 
 'l 
 
 o , 
 22103 
 
 0/1 / ' / 
 
 225 5fl 233 03 237 34 
 
 o / 
 242 S3 
 
 , 
 240 14 
 
 238 41 
 
 2jS 3'a 
 
 24! 4'0 
 
 o , 
 239 32 
 
 23? iV. 
 
 / 
 
 24U 42 
 
 «a 
 
 60 32 
 
 62 43 
 
 72 43 
 
 67 48 
 
 83 23 
 
 77 40 
 
 60 66 
 
 68 21 
 
 04 20 
 
 71 68 
 
 72 17 
 
 69 61 
 
 's 
 
 204 
 
 191 
 
 24 
 
 84 
 
 • 
 163 
 
 64 
 
 64 
 
 CO 
 
 64 
 
 70 
 
 033 
 
 2C1 
 
 224 
 
 «4 
 
 101 
 
 210 
 
 182 
 
 123 
 
 O'J 
 
 127 
 
 183 
 
 226 
 
 243 
 
 104 
 
 07 
 
 •=6 
 
 32 
 
 23 
 
 76 
 
 164 
 
 275 
 
 2S0 
 
 276 
 
 129 
 
 
 
 17 
 
 S3 
 
 16 
 
 'i 
 
 270 
 
 270 
 
 00 
 
 270 
 
 270 
 
 270 
 
 270 
 
 90 
 
 00 
 
 00 
 
 270 
 
 270 
 
 Taking each monthly formuli pepiirately, and Riving to n succes- 
 sively the values 0, 1,2, 3, &c., wo obtain for tliat month the mean 
 normal temperatures for each of the twetity-four hour.H. as far as the 
 normals can be procured from the observations of only throe years. 
 
 The results are given in the following table, in which the numbers in 
 the final column for the year are the arithmetic means from the corres- 
 ponding twelve monthly numbers. 
 
 TABLK II. 
 
 Monthly Mean Normal Temperatures, at Halifax, for each of the twenty-fuur houis, from 
 Hi-hourly Observations in the three yean lS67-e9. 
 
 F£B. MiR. Apr. Mat. Juki. I Jolt 
 
 20 
 18.47 
 20.39 
 22.07 
 23.38 
 24.10 
 
 2 " 
 
 24.38 
 
 3 •' 
 
 23.91! 
 
 4 " 
 
 23.01 
 
 5 " 
 
 21. 8S 
 20. 9S 
 
 6 " 
 
 7 " 
 
 20.37 
 
 8 " 
 
 19.9.') 
 
 9 " 
 
 19.60 
 
 10 " 
 
 19.34 
 
 11 " 
 
 19.13 
 
 Mean 
 
 19.83 
 
 20.90 
 20.32 
 19.74 
 19. ?8 
 
 r.i.(n. 
 
 19.12: 
 
 19.23; 
 
 19.581 
 20.54' 
 
 20. 2(1 ; 
 
 24.30i 
 28.091 
 27.44 
 2S.44 
 29.03 
 28.90 
 27.90 
 20.35 
 24.83 
 23.74 
 23.09 
 22.60 
 22.07 
 21.48 
 
 I 
 
 24.12; 
 
 •2..'..\\\ 
 
 22.09 
 
 21.65, 
 
 21.39 
 
 21.35 
 
 21.04' 
 
 22.83 
 
 24.9s; 
 
 27.05 
 
 30.24 
 
 32.30 
 
 33.67 
 
 34.10 
 
 34.15', 
 
 33.76 
 
 32.681 
 
 ,30.97! 
 
 29.16 
 
 27.67 
 
 26.. '■2 
 
 26.61 
 
 25.03 
 
 24.68 
 
 o 
 
 33.06 
 32.15 
 31.36 
 30.85; 
 .30. 70 1 
 31.001 
 32.12! 
 3:t.94i 
 .36.24] 
 3S.68i 
 40.69: 
 42.77 
 43.83 
 44.91 
 45.1!) 
 44.67{ 
 43.31; 
 41.73 
 39.84; 
 37.70; 
 35.93' 
 34.80 
 34.24 
 33.32' 
 
 42.7.'! 
 42.11 
 41.44 
 
 .40.73 
 
 40.49 
 
 41.33 
 
 43. 2« 
 
 45.71 
 
 46.21 
 
 60,66 
 
 63.02 
 
 64.95 
 
 60.041 
 
 60.24, 
 
 65.90! 
 
 56.65 
 
 64.871 
 
 53. 4«' 
 
 61.14, 
 
 48.49 
 
 4B.,38i 
 
 45.10i 
 
 44.Cfl' 
 
 43.471 
 
 82.7.'ii 
 61.92 
 60.89, 
 6O.O61 
 6>.16! 
 61.61; 
 63.t,9 
 6'i.OSi 
 58.40 
 60.93 
 63.30 
 Co.U'i 
 66.23 
 66.66| 
 60.i!6i 
 66.49; 
 66.08; 
 65.04' 
 62.96 
 59.98 
 67.08 
 65.07. 
 53.99 
 63.38 
 
 Adi. 
 
 Sirr. 
 
 5§.79 
 57.73 
 66.04 
 56.88 
 65.96 
 .57.01 
 58.77, 
 01.03 
 63.78; 
 66.72' 
 69.231 
 70. 90 1 
 71.99 
 72.S1I 
 73.30! 
 73.17; 
 72.33 
 70.81 
 
 OS.. 53; 
 
 05.66 
 62.89 
 00.96 
 60.00: 
 69.451 
 
 ." I 
 
 ■'.8.97' 
 
 •58.04! 
 
 .57.131 
 
 56.63! 
 
 66.01 
 
 57.09! 
 
 ',!•<. Vi' 
 
 60.67; 
 
 63.61 
 
 06.70 
 
 69.17! 
 
 70.78 
 
 71.83 
 
 72.54 
 
 72.88 
 
 72.65 
 
 71.65 
 
 69.84. 
 
 67.37! 
 
 64.63' 
 
 62.19' 
 
 60., 57 
 
 69.87 
 
 69.62 
 
 Oct. Nov. I Dec. 
 
 64.07 42 
 &3.:,3 42 
 62.82:41 
 62.27! 41 
 62.04 40, 
 62.21 140, 
 63.0t!!41 
 64.79!42 
 57.21 44 
 69.85,40 
 62.30 49 
 
 64.21 61 
 
 65.36 52 
 65.92 52, 
 
 60.22 52 
 66.00:52 
 64.7850 
 62.27 48 
 6».4S|46, 
 57.44145 
 66.22 45 
 
 55.37 44 
 54.72 43 
 64.36,42 
 
 .78 '.•!?, 
 ,51 34 
 .86 ,34 
 .16 33 
 .83 33 
 .97,33 
 .49 33, 
 62 33 
 36 31 
 94 ."„■), 
 56 ,37 
 .42,38, 
 29,39, 
 .62..39, 
 77 1 39, 
 .36i39, 
 .88 .",8, 
 .65 '37 
 09 36 
 .65;;i5 
 .10. 35 
 ,37 35 
 .51 34 
 .95 34 
 
 85,23.63 
 05 23.47 
 14 23.28 
 .59 23.06 
 34 23.06 
 38 23.27 
 48 23.46 
 70 23.62 
 45 23.88 
 90 24.91 
 00 26.38 
 
 27.13 37.20: 
 
 48.15J 68.62 64.35J 
 
 64.13; 68.19,46.01 36.02 
 
 .74 
 28.70 
 29.17 
 ■ ,'.04 
 :i,->.28 
 27.19 
 26. 17 
 25.38 
 24.81 
 24.46 
 24.27 
 24.10 
 23.85 
 
 26.21 
 
 Veab 
 
 38.79 
 38.15 
 37.40 
 36.81 
 36.68 
 37.08 
 37.94 
 39.25 
 41.08 
 43.30 
 46.60 
 47.27 
 48.36 
 48.96 
 49.11 
 48.74 
 47.73 
 46.18 
 44.39 
 42.68 
 42.29 
 40.30 
 39.68 
 39.20 
 
 42.33 
 
 If the difference of each hourly normal in excess or defect from the 
 means for twenty-four hours given at the foot of each column be taken, 
 we have the diurnal, variations given in Table III. 
 
ON TUE DIURNAL .ND ANNUAL VAR1ATI0N8 OP 
 
 TAULE III. 
 
 Mtan Diwnal Varlatloni o/TemperaUirc, nl HnVfur, for each month and for thi year, from 
 
 lli-hoiiily Oli3i:rvul!itns in the tjears tHC?-(!'J. 
 
 ::t 
 
 nr^rzi— 
 
 HOUB. 
 
 jAlf, 
 
 Mliln. 
 
 — f.DO 
 
 U.iii. 
 
 — l.M 
 
 2 " 
 
 —2.43 
 
 3 " 
 
 -3.i;i 
 
 4 " 
 
 —3.34 
 
 6 " 
 
 -3.211 
 
 6 " 
 
 -3.11 
 
 7 " 
 
 —3. OS 
 
 8 " 
 
 — 2.r.3 
 
 " 
 
 -1.311 
 
 10 " 
 
 + 0.47 
 
 11 " 
 
 + 2.24 
 
 Noon. 
 
 + 3..'>ri 
 
 1p.m. 
 
 + 4.33] 
 
 2 " 
 
 + 4..'>.^| 
 
 3 " 
 
 + 4.13 
 
 4 " 
 
 + 3.1h 
 
 6 " 
 
 + 2.05 
 
 6 " 
 
 + 1.U) 
 
 7 " 
 
 + 0.&4 
 
 8 " 
 
 + 0.12 
 
 9 " 
 
 —0.21 
 
 10 ■' 
 
 —0.49 
 
 11 " 
 
 —0.70 
 
 One of the uses of Table III. is to supply corrections to the monthly 
 means derived from less frequent observations' at the same station in 
 other years, so as to render them comparable with the means derived 
 from an hourly or bi-hourly series. 
 
 This has been done in the case of the temperatures at Halifax in 
 1870, when the observations were taken at equal intervals of four 
 hours, commencing at 4 a.m. The corrections (which arc very small) 
 were applied to the monthly means for 1870, and the corrected means 
 were then combined with the monthly means for the years 1867, 1868, 
 and 1869, as shown in the following table. 
 
 1870, nncorrecteil 
 
 Corrections for Diurnal Variation 
 
 ISTO, corrected for Diurnal Variation. 
 1867—1870 
 
 Jan. 
 
 29.48 
 + 0.02 
 29. SO 
 22.24 
 
 Feb. 
 
 Mar. 
 
 Apb. 
 
 Mat. 
 
 JCMI. 
 
 23.79 
 + 0.02 
 23.81 
 23.34 
 
 28.63 
 
 —O.OS 
 
 28.45 
 
 27.40 
 
 40.79 
 + 0.02 
 40.81 
 38.10 
 
 40.39 
 +0.03 
 46.42 
 47.72 
 
 59.18 
 + 0.06 
 69.24 
 68.70 
 
 1870, uncorrected 
 
 Corru'Ctious for Diurnal Variation 
 
 1870, corrected foi Diurnal Variation. 
 1867—1870 
 
 ,lni.T. 
 
 AtTd. 
 
 Sept. 
 
 Oct. 
 
 Nov. 
 
 04.50 04.27! M-54 
 + 0.00—0.011—0.09 
 04.021 04.261 fill. 45 
 04.421 64.161 57.76 
 
 48.16: 38.92 
 -0.03 +0.0i 
 48.12; :.8.94 
 46.641 36.75 
 
 D.C. YfAR. 
 
 30.78 
 + 0.06 
 
 44.28 
 
 + 0.01 
 
 30.84, 44.29 
 26.C1| 42.82 
 
 I 
 
 
 ■ -~,,-,.<.viT7-. .■-«--■ 
 
TEMPEUATURE AT HALIFAX, NOVA SCOTIA. 
 
 IIk ytur, from 
 
 IT. Deo. ' YiiAB, 
 
 f.l7-?. 
 
 1.3-1-1. 
 
 I.8S'-1 
 
 J.43|-2. 
 
 ;!.CS-2. 
 
 2.B4I— 1. 
 
 2.54,-1. 
 
 2.3e-l. 
 
 l.,'.7i-l, 
 
 0.12— 
 
 1.58 +1 
 
 2.K1I +2, 
 
 3. .511 +3 
 
 3.811+3 
 
 3.71+3 
 
 3.11+3 
 
 2.(i«, + l 
 
 1.011+0 
 
 0.27+0 
 
 O.lli — 
 
 0.3k 
 
 0.72 
 
 • 1.03 
 
 1.10 
 
 —3,54 
 
 -4. IS 
 
 4.93 
 
 —5.52 
 
 —5.66 
 
 -5.25 
 
 —4.30 
 
 -3.08 
 
 -1.26 
 
 + 0.97 
 
 + 3.17 
 
 + 4.94 
 
 4Ui+fi.03 
 
 981+0.62 
 
 S.t'+0.78 
 
 07 +0.41 
 
 ftSI+5.40 
 
 9(1; +3.85 
 
 17; + 2.06 
 
 40+0.35 
 
 .70—1.04 
 
 .94 —2.03 
 
 .11 -2.66 
 
 .36—3.13 
 
 10 nionthly 
 I station in 
 ns derived 
 
 Halifax in 
 lis of fouv 
 very small) 
 cted means 
 
 1867,1868, 
 
 Jnifi. 
 
 » 
 
 59.18 
 + 0.06 
 69.24 
 68.70 
 
 
 D<C. 
 
 YfAR. 
 
 30.78 
 + 0.00 
 30.84 
 26.01 
 
 44.28 
 
 + 0.01 
 
 , 44.29 
 
 42.82 
 
 
 XT*" 
 
 An interpolating formula being constructed from the twelve monthly 
 means in the lowest line, on the assumption that they are the tempe- 
 ratures proper to the middle dai/s of the several months; if the coeffi- 
 cients calculated on this erroneous assumption bo multiplied respec- 
 tively by the following factor.-!, the expression given below is obtained, 
 in which T„ denotes the daily mean temperature at any time jj, 
 reckoned from January 15, the unit of time being the twelfth part of 
 tho year. 
 
 n 
 
 12 
 
 n 
 
 12 
 
 2lL 
 
 12_ 
 
 . 2 n 
 
 &c. 
 
 n 
 
 V'i 
 
 sin 6 
 
 n 
 
 12 
 
 7' 
 
 :42.82 + 21.82 8111 (»i X 30 + 255.4'») +0.77 sin (2(» X 80+ 66) 
 + 5.18 sin (3u X 30 + 252) + 0.25 sin (in X 80) 
 + 0.89 sin (5n X 3°) + 5) + 0. U sin (6« X 80 + 270) 
 
 From the preceding equation which, by giving suitable values to 
 (n), expresses tho normal daily mean temperature at Halifax on every 
 day in the year, the mean temperatures of the warmest and coldest days 
 are found, together with the days of their occurrence, and the days on 
 which the daily mean passes through its mean annual value. 
 
 Warmest day, August 28. Mean temperature, 6-4°.90. 
 
 Coldest day, January 13, 14. Mean temperature, 21°.95. 
 
 In Spring, tho mean of the day is below the mean of the year on 
 April 29, and exceeds it on Ap.ll 30. 
 
 In Autumn, the mean of the day passes through its annual value 
 between October 25 and October 26. 
 
 TABLE IV. 
 
 
 
 
 
 
 COUBIilATION. 
 
 Jaw. 
 
 +0.41 
 +0.25 
 +0.32 
 
 Feb. 
 
 ..:.-.. 
 
 Apr. 
 
 + 0.78 
 —0.02 
 —0.02 
 
 Mat. 
 
 Ju.ll. 
 
 
 
 ! 
 
 + 0.56i+0.49 
 + 0.27-0.08 
 +0.20-0.19 
 
 +0.77 +0.76 
 —0.18 —0.30 
 —0.32 —0.41 
 
 
 7 2, 9. 9 
 
 
 rt 2 in 
 
 
 
 
 COMBINATI M. 
 
 July. 
 
 ACQ. 
 
 Sept. 
 
 OOT. 
 
 Not. 
 
 Deo. 
 
 Year. 
 
 ArithmeUo Means from 7, 2, 9 
 
 7, 2, 9, 9 
 
 e 2 10' 
 
 +0.75 
 -0.29 
 -0.33 
 
 + 0.54 
 
 —0.48 
 !— 0.44 
 
 +0.60 
 —0.25 
 -0.19 
 
 +0.64 
 —0.00 
 —0.09 
 
 +0.22 
 —0.01 
 + 0.05 
 
 +0.40 
 +0.06 
 +0.32 
 
 +0.6S 
 -0.09 
 —0.09 
 
 
 
 1 
 
 
ON THE mUKNAL AND ANNUAL VAU1ATI0N8 OF 
 
 In Table IV are shown tho errors in the approiJmnto monthly means 
 whrn the daily moan is considered as the simple arithmetic means of 
 tho tcmpcraturcH observed nt 7 a.m., 2 p.m. and p.m., and of those 
 observed at G a.m., 2 p.m. and 10 p.m. ; atid also when the daily mean 
 is taken as c(\\u\.\ to the fourth part of the sum of tho temperatures nt 
 7 a.m., 2 p.m., and twice the temperature at 9 p m. 
 
 It is seen that tho arithmetic nieim of observations at 7 a.m., 2 p.m. 
 and y p.m., gives a result too hi-h by 0." jG on the average of all 
 months, and nearly eight-tenths too high from April to July, 
 
 Tho arithmetic mean of observations at G a.m., 2 p.m. and 10 p.m., 
 is in no ca.se more tlnn half a degree in error; it is too high from 
 November to lu-bruary, and too li.w during the re.^t of tho year, tho 
 average error irrespective of sign being a quarter of a degree, and tho 
 error in t!ic annual moan less tliaii one-tenth in defect. 
 
 When the observation at 9 p.m. is reckoned licicc, the greatest error 
 which occurs in any month is slightly greater, but the average error of 
 the twelve monthly means, tho signs of tho errors being disregarded, 
 is 0.° 18, and the error in the annual mean the same as in the 
 preceding ease. 
 
 These results accord in their general character with tho experienco 
 of other places at which tho observations have been sufficiently frequent 
 for determining tho dlurntil variations. 
 
 As regards suitability for yielding daily means, 7, 2, 9, 9, and G, 2, 
 10, may be regarded as of nearly equal merit ; and as 7, 2, 9, are in 
 many respects mure convenient to observers than the other combina- 
 tion, and less liable therefore to iiitonaptiHis, these hours arc recom- 
 mended to those observers in Canada who read their instruments three 
 times each day.* 
 
 The numbers in Table III, as the title states, are tho monthli/ means 
 of the diurnal variations, and are only adapted therefore for the reduc- 
 tion of monthli/ means at single hours to monthly means for all hours, 
 and for the converse reduction. Comparison of like hours in contiguous 
 months will show a considi. ruble uillcreucc in the analogous variations. 
 To correct daili/ means, therefore, it is necessary to possess tables in 
 which diurnal variations are ,;,'ivon at much shorter intervals. As 
 tiiree years is scarcely r,uf"ieioiit for tho elimination of accidental irre- 
 gularities, the computation of the diurnal variations for every fifth day 
 
 'tea^w 
 
 * 7 a.m., 2 p.m. and 9 v-m., have been aaoptea for m»uy years by the Smithsonian Institution. 
 
,, 2 p.m. 
 
 TKMrKnATURK AT HALIFAX, NOVA 8t'l>TIA, J 
 
 has been postponed till at least two nioro years have been added to the 
 scries. For a like reason, the discussion of (juestions relating to the 
 comparative vavinbility of didoront niuntlis, and of daily means at diffe- 
 rent parts of the yoar, bus nut bet'ii luidprtakeu. Tho collection of 
 suitable materials for Halifax is howovcr in progress, as Mr. Allison 
 has been observing at c(iunl intorvais of tbrco hourssinco the begin- 
 ning of 1871. 
 
 It was stated at tlic coinuicnccnicnt of this article, that besides the 
 corrections for diurnal variations, or those needed to compensate for 
 tho insufficient frequency of tho observations, corrections are also 
 required in order that observations taken during a few years may be 
 rendered comparable with those continued during a long aeries of years. 
 In procuring data for the second class of corrections some other 
 observers have made considerable progress ; but in order to give full 
 effect to their past work, it is requisite that they should undertake for 
 u few years at least equidistant -observations at intervals not exceeding 
 three hours. Among these, Mr. Murdoch, C. E., of St. John's, New 
 Brunswick, who has been actively engaged in Meteorology for more 
 than ten years, is about, it is believed, to commence a system of three- 
 hour intervals. Should he persevere .in this undertaking for four or 
 five years, his series will be inferior to that of no station now in corres- 
 pondence with Toronto. 
 
 It is much to be desired also that a three-hour system could be esta- 
 blished under Dr. Smallwood, at Montreal, and Capt. Ashe, at Quebec, 
 in order that their observations in past years may be more effectively 
 utilized. 
 
 In connection with the subject of diurnal variations it is satisfactory 
 to mention that, through the kindness of the Rev. Dr. Fyfe, President 
 of the Canadian Literary Institute, the Baptist College at Woodstock, 
 Ontario, Mr. Montgomery, tho mathematical tutor, with other officers 
 of the establishment, have been engaged for some months in taking 
 observations of the temperature, day and night, at equal intervals of 
 three hours. Mr. Montgomery is fully alive to the importance of accu- 
 racy j and as his arrangements are very excellent, it is anticipated that 
 valuable aid will be supplied by his labours towards the reduction of 
 observations in other parts of West Ontario. 
 
L 
 
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