July 7, 1887] 



NATURE 



227 



M 



have derived from the applications of science, they are 

 nothing as compared with those which will and do accrue 

 to us from the acceptance of scientific habits of thought. 

 That is coming already, and it will come more in a not 

 remote future. We have many things in this age and 

 country of which we cannot boast, but we may boast that 

 in science England has done something more than hold 

 her own. The great name of Darwin will survive, it may 

 be, the British Empire itself, and with him will be re- 

 membered some others also, whom to single out might 

 perhaps be invidious. But we may be sure of this, that 

 among their names will be included the name of our dis- 

 tinguished guest of to night. It is «. common complaint 

 that politicians have done nothing for science. In that 

 I do not agree. They have done the best they could for 

 it— they have let it alone; they have not corrupted it by 

 their intrigues, nor vulgarized it by their squabbles ; and 

 they being what they are, and science being what it 

 is, that is probably the best service they could have 

 rendered it. 



Lord Rayleigh proposed "The Health of the Chairman." 

 Piof Stokes briefly responded, and the company, which 

 numbered nearly two hundred, separated. 



THE ELEVEN-YEAR PERIODICAL FLUCTUA- 

 TION OF THE CARNATIC RAINFALL. 



ORE than fourteen years ago, in the pages of 

 Nature, Mr. Norman Lockyer first drew atten- 

 tion to an apparent periodical variation of the rainfall 

 registered at the Madras Observatory ; which seemed to 

 be such that it reached a maximum and a minimum 

 alternately, at about the same epochs as the corresponding 

 phases of the sunspot frequency. The idea, once started, 

 was followed up by others, among whom perhaps the best 

 known is Dr. (now Sir) W. W. Hunter, whose pamphlet 

 on the subject, without laying claim to any originality as 

 regards its subject matter, attracted very general attention 

 by the charm of its style, and also by its attempt to 

 identify the periodical occurrence of famines in Southern 

 India with the epochs of minimum rainfall shown by the 

 Madras registers. 



When, however, the data on which these speculations 

 were based came to be critically examined, the general 

 verdict of men of science was that the conclusions were 

 " not proven." This was certainly my own opinion ; and 

 General R. Strachey, in a lecture delivered before the 

 Royal Institution in 1877, and, at greater length, in a 

 paper communicated to the Royal Society in May of the 

 same year, showed that any attempt to educe a true 

 cyclical variation from the recorded figures, ended in a 

 negative result. Admitting that when the annual quanti- 

 ties were tabulated in eleven-year cycles, .the means of 

 the homologous terms seemed to indicate a period of 

 maximum between the third and seventh years, and of a 

 minimum between the eighth and second years, he found 

 that, when the mean difference of the individual years 

 from the supposed periodical means was co:npared with 

 the mean difference of the former from the arithmetical 

 mean of the whole series, the results differed but little. 



It was further shown by myself that the supposed con- 

 nexion between the periodicity of the Madras (Observa- 

 tory) rainfall and that of famines in Southern India was 

 by no means so intimate as might appear at first sight. 

 The famines in question had occurred sometimes in one 

 part of the peninsula, sometimes in another, by no means 

 always in the country around Madras ; but no other 

 station in the peninsula (of those then available for the 

 inquiry) showed even such an approach to a periodical 

 variation of the rainfall as did the Madras Observatory. 



At this stage matters have since remained, with the 

 exception that, in 1879, an apparent periodical fluctuation 

 ^a very different character was brought to notice by 

 ^^srs. Hill and Archibald in the winter rainfall of 



Northern India. This, which has an interest of its own, 

 I shall not further discuss at present. 



In the course of a general investigation of the rainfall 

 of India, the first part of which only ha? been as yet 

 published (" Indian Meteorological Memoirs," vol. iii. 

 part i), I have lately had occasion to reconsider these old 

 questions, and to re-examine them by the light of the 

 accumulated data of the last twenty-two years. For 

 convenience of discussion, I have divided India and 

 Burmah into twenty-four rainfall provinces, one of which 

 is the Carnatic. 



This consists of the plain below the Eastern Ghd.ts, occu- 

 pying the south-east of the peninsula, and extending from 

 Cape Comorin to the mouths of the Kistna. Its area may 

 be taken as 72,000 square miles. The town of Madras is 

 situated nearly midway on the sea-coast of this province, 

 and is a fairly representative station ; but, in addition to 

 the rainfall registers of the Madras Observatory, I have 

 those of thirty-nine other stations, pretty equally dis- 

 tributed through the province ; most of them extending 

 back to 1864. The Carnatic is distinguished by one 

 important peculiarity in the season of its chief rainfall. 

 During the spring months, it receives a certain amount of 

 rain, in common with the southern and eastern provinces 

 of India generally ; but while the heavy summer rains 

 are falling in Central and Northern India, and also on the 

 west coast of the peninsula, the Carnatic is but little 

 affected by them. In its southern districts, indeed, the 

 rainfall of June and July is less than that of May ; and it 

 is not until the rains are over in North-Western India, 

 viz. in October and November, that this province receives 

 the chief and heaviest rainfall of the year. Hence 

 the vicissitudes of the rainfall of the summer months, 

 which are all important in Central and Northern India, 

 are relatively less important in the Carnatic, even if they 

 affect that province in the same manner as Northern 

 India — and this is far from being always the case — and as 

 a final result the annual fluctuation of the Carnatic 

 rainfall often differs widely from that of other provinces in 

 the peninsula. 



The mean annual rainfall of the Carnatic may be 

 taken in round figures at 35 inches, which is about 7 

 inches less than the general average of the whole of 

 India. The following table gives the annual variation 

 from this average for the twenty-two years 1864-85, 

 which results when the annual total fall of each mdi- 

 vidual station is compared with its local average, and the 

 mean of all the differences taken for each year. 



Annual mean rainfall variation of the Carna'ic rainfall. 



During the first thirteen years (with the exception of 

 1873) the fluctuation, here shown, is remarkably distinct 

 and regular. The rainfall reached a minimum in 1867, 

 then rose steadily to a maximum in 1872, and after a 

 drop in 1873, and partial recovery in the following year, 

 fell rapidly to a second minimum in 1876. From 1877 to 

 1881 it oscillated considerably, but thereafter rose again 

 steadily to a second maximum in 18S4, dropping again in 

 1885 to something below the average. Thus we have, 

 apparently, two complete cycles in the twenty-two years ; 

 the first remarkably regular, the second less so, but with 

 the periodical fluctuation still dominant. 



In order to ascertain with somewhat greater precision 



