67 



AXALYSIS OF THE OBSERVATORY RECORDS FOR JULY, 1864 ; 

 IN CONJUNCTION WITH THOSE OF BIRTHS, DEATHS, &C. By 



E. SWABBRECK HALL. 



The general character of the weather this month was abnormal and more 

 deaths took place than in any Jidy of the previous seven years, except that of 

 1800 when so many old people were carried off by influenza. 



Atmospheric pressure mean is, 29 "856, and so nearly that of the 20 years' 

 standard average, that it only differs by being below it two thousands of an 

 inch. The maximvmi pressure was, 30.369, on the 2nd ; and the minimum, 

 29.338, on the 25th, consequently the range of the month was, 1'031 inches. 

 The greatest movement of the barometer on any day, was a fall of, — '447 of an 

 inch on the 17th, with a strong south wind and heavy fall of rain. The greatest 

 rise was + "415 of an inch on the 27th. On eleven other days there were move- 

 ments exceeding one-fifth of an inch. In July 1863, while the extreme range 

 of the month and the daily perturbations were much the same as in the present 

 month, the month's mean pressure was considerably less. 



The total v:ind-force wa.s 31 "21 lbs., which is — 7 '42 lbs., less than the average 

 of the previous seven years. July 1863 had 93 lbs. — south and south east winds 

 were the only ones which had an excess both in frequency and force. This 

 occurred with the heavy rains from the 16th to the 19th of the month. At the 

 evening observation on the 17th, the wind pressiire was 5 "21 lbs., to the square 

 foot, being the maximum of the month. At four other observations within this 

 period, 2 "60 lbs., pressure was recorded, and this amount was only once 

 registered during any other day of the month. North-v;est winds were more 

 ihka usually frequent, 48 out of the 93 observations, but they were so faint, 

 that the whole pressure was less than the avei-age. North, North-east, Efxst, 

 South-v;est, and West, were all below the average both in frequency and force. 

 There were 47 calms noted, being + 7 more than the average for July. Last 

 year's July had only 24 calms. 



Teiwjsrm^ure mean was, 49" 15 degrees, being +3.33 degrees above the 20 

 years' mean, and warmer than any July on record. By the self -registering 

 maxima and minima thermometers, the mean was 49 82 degrees, being an 

 unusually close approximation, to that by the three daily observations. The 

 extremes of temperature recorded were, 63 on the 2nd, and 34 on the 28th. So 

 small a range had not occurred for nine years previously. In July last year the 

 extremes were 70 and 32. 



The dail7/-ran{/e mean was, 17*32 degrees, being + 1*97 above the 20 years* 

 mean, and yet almost identical with that of July 1863. The greatest range on 

 any day was, 26 degrees on the 2nd ; and the smallest was, 5 degrees on the 

 18th and 19th, during the heavy rains. The mild and equable temperature 

 prevailing, while so much rain came with strong winds from southerly points of 

 the compass, is most remarkable. From the evening of the 15th until the 

 evening of the 20th every one of the three daily records noted the wind from 

 some southerly point, yet the mean temperature of these six days, exceeded 

 the mean temperature of the month, being nearly 51 degrees. 



Solar-intensity ranged from 92 maximum on the 22nd, to 54 minimum on the 

 17th. The mean was, 77*74 degrees, being + 2*69 degrees higher than the 

 average of the previous 8 years, and above any of them except 1855. In 1863 

 the mean was — 5*78 degrees less than the present month. The cloud mean 

 being, moreover, above the 20 years' average, makes the sun's rays, while pre- 

 vailing, so much the hotter. 



Terrestial-radiation mean was, 37*35 degrees, which is + 2*22 degrees above 

 the average of the previous eight years and higher than any one of tlvem. The 

 maximum was 49 degrees on the 19th ; and the minimum 30 degrees on the 

 26th and 28th. The latter was higher than any minima of the previous eight 

 years. The extremes in July 1863, were 45' 4 and 27 degrees. 



Bain-fall amounted to 4*44 inches, being + 2*71 inches more than the 20 

 years' mean. Two July's only in the jjrevious 23 years had more than this, 

 i.e., last year : — 5*62 inches, and 1849 — 5*99 inches. However, in the present 

 month my rain gauge record is, 5*42 inches, — or nearly an inch more than fell 

 in the centre of the city, as registere^l at Mr. Abbott's observatory. The rain 

 was registered on 12 days, which is rather more than two less than the average 

 of the previous nine years— 1863 had 19 ; 1862—18, and 1861—20 days wet. 

 Moreover the rain this month fell nearly altogether.on five days, i.e.: — the 8th, 

 17th, 18th, 19th and 20th. For the other seven days altogether, only, *19 of an 

 inch is registered ; mere sprinkles on any day. From 10 p.m. on the 16th, to 

 10 p.m. on the 17th, I measured from my rain-gauge 3*40 inches, and in the 

 next twenty-fours '90 of an inch. Floofls prevailed throughout the island, and 

 the Hobarton rivulet and drains had a thorough cleansing. 



Snow was never absent from Mount Wellington during the month, under- 



