182 Meteorological Observations at the Madi a* Observatory. 



The mean atmospheric pressure through >ut the whole year was 29*830 

 inches ; — 0 014 less than the average of tweuty years. The highest reduced 

 leadings were 30*018 on February 12th, and 301 23 on December 31st :— 

 the lowest was 29*508 on June 29th. 



The greatest degree of heat registered in the shade, was 107°" 1 , on May 

 30th : in full sunshine, three feet from the ground, 124"' 5 >>n May 17tb. 

 The lowest temperatures were recorded on February 2/ih and December 

 3 1st, on which days the shade minimum went down to 63 3 5aud 62 3, 6, 

 and the grass thermometer to 58 3 3 and 56 3, 9 respectively. The meau 

 annual temperature was 813,or 07 above average. That of evaporation, 

 as shewn by the wet bulb thermometer, was 74 9, or 0 9 above average. 

 The mean daily range for the year was 14°5. 



The dryest day in the year was June 12th, when the percentage of 

 humidity fell so low as 42, and the mean dew point was 63°'l, or 27°"4 

 less than the mean temperature of the day. Complete saturation of the 

 atmosphere occurred but once, viz , on October 31st. 



Rain fell on 96 days- The quantity measured was above one inch on 

 113 days, but the greatest fall was only 3 23 inches, on December 14th. 

 The total fall during the year was only 38 18 inches, leaving a deficiency 

 of 12 - 57 inches or exactly oue-fourth of the whole yearly average. 



The mean daily velocity of the wind was 151 miles, from S E by S. 

 It was recorded half daily, and ranged between 165 miles on May 22ud y. m., 

 and 14 miles on October 20th a. m. It is worthy of remark, that, al- 

 though the wind at Madras is insignificant in comparison of that in Eng- 

 land, it is far more constant, and rarely ever quite still. Not one single half 

 day lias been perfectly calm since the velosity gauge was first pur, up, on 

 September 1st 1861. During the steadier mouths of the year, the result- 

 ant velocity, or that in which the force from each point of the compass is 

 taken into account, often nearly equals the mean velocity, and rarely falls 

 short of three-fourths of the latter quantity. In the two variable periods 

 iiowever, the difference is very con^derable. Thus, in the latter half of 

 Much, while the actual daily wind was 125 miles, from N N E, 

 the resultant value was only 40 miles, from East ; but in the latter half of 

 October, when the daily moi ion was 116 miles from S E, the resultant 

 value was only 3 miles per dty, from S S W. This re.narkable effect of 

 contrary winds must surely lnve considerable influence upon t he public 

 health and mortality returns ; since any miasmatic v*pors existing in the 

 at nosphere at the time, though stirred up aud diffused by the act ual daily 

 wind, will still be blown backwards and forwards, so as to con'iniv hm^ing 

 about, or at least only very slowly receding from, the sau.e spot ; while at 

 other times they would be wafted a thousand miles off in ies3 than a 

 single week. The number of half days the wind blew from each point of 

 the compass is given in the following table : — 



North 3 1 JEast 14 



Nby E 28 Eby S 13 



K N E 30 E SE 17 



NEbv N 42SE by E .... 11 



North East.... 16ISouth East.... 21 



N B by E 32|S E by E 33 



ENE 21 S S E 60 



E by N 13 ( S by E 44 



hiuu, N E Qmrter il3.|Ffom 3 B Quarter 216. 



South •.. 47! West 5 



SbyW 36WbyN 3 



SSW 41 W N W 4 



S Wby S 42 N W by W.... 1 



SouthWest... 32 North West. ..; 2 



S W bv VV... 32 N W by N * 



W S W 19 N N W 9 



Wby S UMbj W li 



from S W Qua rter 26Q.|From H W Qqarter 41 



NORMAN ROBERT POGSON, 



