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ANALYSIS OF THE OBERVATORY RECORDS FOR DECEMBER 

 1864, IN CONJUNCTION WITH THOSE OF BIRTHS, DEATHS, 

 &o. By E. Swarbreck Hall. 



The year 1864 closed with weather less fatal to life than any December of 

 the previous seven years, 1860 had previously the minimum mortality, though 

 December 1863 had only one more death than it had. 



Atmospheric pressure had a much smaller range and fewer perturbations 

 than in either the preceding month of November or in December 1863. The 

 mean was 29 '839, being +*069 above the 20 years' adopted standard mean, 

 and higher than any December since 1860. The extremes were 30 291 

 maximum on the 6th; 29*329 minimum on the 9th. The month's range '962 

 being — '317 less than December, 1883, had. The greatest movement of tha 

 bai-ometer on any day of the month was a rise of + 468 of an inch on the 4th. 

 The greatest fall was — •4.54 on the 9th. Besides these there were only eight 

 other days having a movement exceeding one-fifth of an inch, and none of 

 them extending beyond one quarter of an inch. Atmospheric pressure, there- 

 fore, was not adverse to life, as it was in November. 



Wind pressure amounted to 94 '44 lbs., being +6*20 lbs. more than the 

 December average of the previous seven years. December 1863, however 

 was still more windy. The three s outherly points of the compass had 48 out 

 of the 93 observations, and 53*03 lbs. of the total strength. Of the other five 

 points north-west had 20 out of the 45 winds, and 28 37 lbs. out of the 41*38 

 lbs. of force. The strongest wind noted had 10*42 lbs. pressure to the square 

 foot, and occurred on the 10th ; being a north-west gale but not a hot wind. 

 It IS a remarkable and unusual fact that there was not* a single hot wind in 

 all 1864. Calms were recorded 11 times, being —3*33 less than the average of 

 the previous seven years' Decembers. Aerial movement, therefore, was inuch 

 more propitious to health than in November, for though having a less total 

 force, the predominant winds were from the purest quarters. 



Temperature mean, 59*29 degrees, is —2*78 degrees below the 20 years' 

 average, and colder than any December since 1852, when the mean was 53*13 

 dejaees. Though the present month has little more than one degree higher 

 mean than November had, it differed widely in the distribution of its heat. 

 November had wide extremes, and a great daily range. December was much 

 below it in both respects. The maximum temperature was only 78 degrees 

 on the 9th and 23rd, and the mean of all its maxima, only 68 58 deorees ♦ 

 while November's maximum was 8.5, and the mean of its maxiraa°70*13 

 degrees. The December minimum was 40 degrees, recorded on the 4th ; and 

 the mean of all its minima 5 1 -9;) degrees. November was respectively 4i and 

 48-76 degrees. Cold and wet Decembers have always had fewer deaths than 

 warm and dry ones. December 1863 came under the former category. The 

 mean temperature by the self -registering thermometers differed less than one 

 degree from that of the thiee daily records, being 60 '24 degrees. 



The mean daily range of temperature was only 16*67 degrees, being— 3 88 

 degrees below the 20 years' average for December. It was also about°haIf a 

 •degree less than that of December 1863, being another more favorable meteo- 

 rological condition to account for the smaller mortahty of the present month 

 The greatest range on any day was only 24 degrees, on the 7th and 14th • and 

 the smallest 4 degrees on the 28th, Dacember 1863 had as low a minimum 

 but 12 degrees higher maximum. None of the twenty -three Decembers on 

 record had so small a maxinmm as the month under review, the ran^-e being 

 from 28 degrees in 1862 to 42^ in 1847. The preceding month of November 

 had a maximum rangel3 degrees higher than that of the present month. 



Solar intensity mean was only 100*51 degrees, being— 4*10 degrees less than 

 the average of the previous eight years, and —3*35 less than the previous 

 month had. December 1863, however, had a few decimals less, and 1861 was 

 only 99 degrees. The unusually cloudy character of the present month in 

 great part accounts for so small a mean. At the same time the maximum 

 only attained 121 degrees, on the 17th, being 4 degress less than November 

 had, and less than six out of the eight years had. 1863 had the maximum 136 

 degrees, and 1861-2 had the minima, being respectively 117-116. The minimum 

 record of the solar-thermometer wa» 61 degrees oo the 29th, being a cloudr 

 w«t day with a cold south wind. 



