Feb. 7, 1884] 



NA TURE 



339 



point of view, was that in 1879 the monsoon rains were 

 unusually heavy, while in 1880 they were so scanty that 

 for a long time gf^ve apprehensions were entertained of 

 another famine, like that which followed the drought of 

 1877. The year 1877 (which does not appear in the 

 table) was an extraordinarily healthy one, but the effect 

 of the scarcity produced by the drought of that year is 

 seen in the high mortality of the first six months of 187S. 



The first rough generalisation suggested by the table is 

 that dry years are healthy and wet ones unhealthy. That 

 this is generally true is well known to residents in the 

 country. Among the natives also I have heard it said 

 that one must choose between health plus famine and 

 abundance plm fever. It would nevertheless be false to 

 infer that in India mortality is due to rain ; for we have 

 only to compare the figures for the several months to see 

 that on the average, and in almost every single year, the 

 month in which fewest deaths occur is July, which 

 happens to be just the rainiest month of the twelve. Rain 

 is no doubt one of the indirect causes of death ; but it 

 seems to produce unhealthy effects by increasing the 

 humidity of the air and hastening the growth of rank 

 vegetation, which, decaying at a time of the year when 

 the air is almost perfectly still over the Indian plains, 

 produces that noxious condition of the lower atmospheric 

 strata known by the name malaria. Compared with the 

 deaths from malarial fevers, those due to cholera, small- 

 pox, and other epidemics count almost as nothing. 

 Hence, though these epidemics have their particular 

 seasons of maximum and minimum, their effect is com- 

 pletely hidden in the general mortahty table under the 

 great annual variation which culminates in October and 

 November. 



Besides rainfall, atmospheric humidity, and wind velo- 

 city, other meteorological causes which presumably have 

 some effect upon health are the mean temperature and 

 the daily range of temperature — the last, according to the 

 prevalent opinion amongst Indian medical men, who are 

 fond of attributing almost every ailment to nocturnal 

 chills, being a most important cause. The next table 

 gives approximate monthly mean values of all these 

 meteorological elements for the North-West Provinces 

 and Oudh, exclusive of the Himalayan districts, which 

 are very sparsely populated. 



Mean Values of Certain Climatological Factors in the North- West 

 Provinces and Oudh 



April 

 2480 



May 

 2397 



June 

 2181 



Jan. Feb. March 



2351 2201 2093 



July Aug. Sept. Oct. Nov. Dec. 



1S55 243s 3040 4352 4083 3025 



It has already been pointed out that the effect of the 

 rainfall upon health is very indirect, and therefore need 

 not be taken into account here. The relative effects of 

 the other factors in the second table may be calculated 

 approximately by the formula — 



d = at -^ ^r -^ yh \ Iv. 

 Here d, t, r, h, and v respectively denote the variations 

 of the death rate, the mean temperature, the range of 

 temperature, the relative humidity, and the wind velocity 

 each month from their mean annual values. From the 

 twelve equations of this form, furnished by the monthly 

 means, we get the following most probable values for the 

 coefficients, viz. : — 



I & - H3'6 



Before proceeding to estimate the relative effects of 

 these factors upon the death rate, it will be found con- 

 venient to convert the totals given in the first table into 

 mean rates per annum. The mean number of deaths per 

 annum for each million of population is 32,493, and this 

 number is distributed over the months as follows, when 

 the months are all reduced to the same length : — 



797 



35-6 



1 = 43'4 I 



If there be any approach to truth in the assumed propor- 

 tionality between the variations of the death rate and of 

 these climatological elements, it therefore appears that a 

 mere rise of temperature within the limits observed pro- 

 duced comparatively little effect, one degree of increase 

 in the mean temperature increasing the deaths about 80 

 per million per month, or rather less than one per 

 thousand per annum. The variations of the diurnal 

 range have a much greater effect, while the change of the 

 death rate due to varying humidity is even less than that 

 due to temperature changes. 



The relation between the death rate and the movement 

 of the wind is inverse, the proportionate increase of 

 deaths being 35 6 per million per month for a decrease 

 in the velocity of the wind amounting to only one mile in 

 twenty-four hours. In the months of October and 

 November, when so-called malarial diseases attain their 

 maximum, the air is almost absolutely still ; and there 

 can be very little doubt that if a moderate breeze were 

 occasionally to spring up at this time of the year, so as to 

 dissipate the malaria, or at all events mix it with good 

 air from other districts or from above, the effect would be 

 an immediate decrease of the death rate. 



As regards special causes of death, I have already 

 stated that I have confined my attention to those cases 

 in which the chaiikiddr may be trusted to make a correct 

 diagnosis. Small-pox, a disease now happily almost 

 banished from Europe, but still carrying off many thou- 

 sands of victims annually in India, is one of these almost 

 unmistakable causes. The average number of deaths 

 from this disease during the five years was 59,240, distri- 

 buted as follows : — 



The deaths from this cause, numerous as they are, are 

 fewest in the months when the general mortality attains 

 its maximum. The meteorological causes which favour 

 the spread of small-pox appear to be heat, drought, and 

 possibly also an unusually high wind velocity, the solid 

 particles which constitute the contagion being presumably 

 blown about by the wind. The relative effects of these 

 may be roughly computed from the totals for each 

 quarter, using the formula — 



n = N+ at + )3(loo - h) + yv; 

 n being the recorded number of deaths in any month ; 

 N the number that would occur under the hypothetical 

 conditions of a still, saturated atmosphere at 0° F. ; and 

 /, /?, and -J standing for the temperature, humidity, and 

 vvind velocity respectively. The coefficients thus found 

 ^ve a = 91 ; /3 = 237 ; y = 97 ; the condition most favour- 

 able to the 'propagation of small-pox appearing therefore 



