422 



Mr. H. F. Blanford. The Diurnal Barometric 



In the rainy season there were 2929 rainy hours in the seven years, 

 giving an average of 122 for each hour of the day. But for the hour 

 between 10 and 11 p.m. there were but 73 instances of rain, or but 

 two-thirds of this average, and from 8 to 9 a.m. but 91 instances of 

 rain, or three-fourths of the average. The deficiency in the quantity 

 of the rainfall was even more striking. The average per hour of the 

 day was 12*81 inches, but the recorded amount for the hour between 

 10 and 11 p.m. was only 4*76 inches, or less than two-fifths of the 

 general average, and that from 9 to 10 a.m. was 8 - 46 inches, or little 

 more than two-thirds. 



Another equally striking example of the approximate coincidence of 

 interruptions of the rainfall, about the time of the diurnal maxima of 

 pressure, is afforded by Batavia, on the evidence of ten years' registers 

 of the hourly rainfall, published by Dr. Bergsma in the 3rd volume 

 of the ' Batavia Observations.' Here also, it is only the rainy reason 

 (December to January) that exhibits this feature in a very decisive 

 manner, and the coincidence is the more remarkable, since, in another 

 respect, the diurnal variation of the rainfall of Batavia stands in 

 marked contrast to that of Calcutta. At Calcutta the greater 

 proportion of the rain falls in the daytime ; at Batavia at night. 

 The percentages were respectively as follows : — 



Calcutta. Batavia. 



From 6 a.m to 6 p.m 60'3 per cent. 47*8 per cent. 



From 6 p.m. to 6 a.m 397 „ 52*2 „ 



And the Batavian maximum follows the minimum within four honrs, 

 in the proportion of 5 to 2. The following table gives the total 

 rainfall in millimetres, recorded at each hour of the day of the three 

 rainy months during the ten years 1866-1875 (Sunday excepted), and 

 in a parallel column the smoothed values computed as in the former 

 case. The curve, fig. 6, is drawn from these latter fignres. 



Total Hourly Rainfall at Batavia (December to February), ten years. 



Hours. 



Observed. 



Computed. 



Hours. 



Observed. 



Computed. 







mm. 



mm. 







mm. 



mm. 



Midn. to 1. . . 



571 



550 



Noon to 13. . . 



364 



374 



1 



„ 2... 



584 



547 



13 



„ 14... 



423 



413 



2 



„ 3... 



448 



489 



14 



„ 15... 



413 



403 



3 



„ 4... 



478 



451 



15 



„ 16... 



362 



394 



4 



„ 5... 



401 



452 



16 



„ 17... 



439 



432 



5 



„ 6... 



527 



472 



17 



„ 18... 



486 



446 



6 



„ 7... 



435 



445 



18 



„ 19... 



373 



385 



7 



n 8 '" 



382 



401 



19 



„ 20... 



307 



312 



8 



„ 9... 



404 



392 



20 



„ 21... 



263 



266 



9 



„ 10... 



379 



362 



21 



„ 22... 



231 



308 



10 



„ 11... 



„ noon . 



288 



326 



22 



„ 23... 

 midn. 



508 



431 



11 



351 



338 



23 



475 



507 



















