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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 ■.■i5SSs!s3^as»SFW-;««*8W*®BSa(aa*£?isS^S^