400 



NA TURE 



Feb. 24, 1 88 1 



would no doubt be correct ; but this relation between pressure 

 and rainfall, strange though the fact may appear, does not appa- 

 rently hold in the winter in the sub-tropical region of Northern 

 India, nor is famine always caused in this region by a failure of 

 summer rain alone. 



For as Mr. S. A. Hill has shown in a paper on "Variations 

 of Rainfall in Northern India" ("Indian Meteorological 

 Memoirs," No. vii. p. 204), a heavy winter rainfall generally 

 coincides with a high .barometric pressure over Northern Indi;i, 

 and vice versa, while two of the most severe famines in Mr. 

 Chambers' list, viz., those of 1837-3S and l86o-6l, in Northern 

 India were caused by " a partial tailure of the summer raiii>, 

 followed by an almost complete ab.^ence of the usual winter 

 fall." 



It is straining the evidence therefore to attempt to relate the e 

 famines, as Mr. Chambers has done, to the previoics occurrence 

 of high barometric prcsiires, since if ihe law just quoted held 

 good, the famine of 1S60-61 was mainly due to the absence of 

 winter rain, caused by the kw pressure which observations show 

 actually existed at that time, and the same was very probably 

 the case in 1837-38, a strongly-marked epoch of sun-spot 

 maximum. 



It has moreover been shown by Mr. Hill in the paper just 

 referred to that "the summer rains of the North- West Provinces 

 and Rajpootana have failed quite as often when sun-spots were 

 numerous as when they were few, but whereas in the former 

 case a comparatively slight scarcity has generally been developed 

 into a severe famine through the Irdlure of the winter rains, this 

 has seldom happened in the latter case, the distress at such 

 times being alleviated by the in-gaihering of the rabi harve.;t, 

 rendered more abundant than usual by a copious winter fall." 

 This saving clause with respect to the winter rainfall of Northern 

 India does not unfortunately apply to Southern India, where 

 failure of the usual monsoon supply means drought and probably 

 famine until the next monsoon, i c. for an em ire year. 



On the whole it is plain that high and low atmospheric 

 pressures differ specifically in their effects in different parts of 

 the Indian peninsula, since while the former is generally as >- 

 ciated with drought in the southern province^, the latter in the 

 winter is almost equally fatal in the northern provinces. If 

 therefore the future prevision of famines is to be based on the 

 empirical law connecting high barometric pressure with the occur- 

 rence of drought and famine, propounded by Mr. Chambers, it 

 must be remembered ihat this law strictly applies only to regions 

 where the annual water-supply is dependent upon the momoons 

 alone, and therefore lying for the most part between the two 

 tropics. 



It may be remarked that at least half of the Indian peninsula 

 lies north of the tropic of Cancer. 



Til' ugh I am sceptical as to the idea of motion from west to 

 east, conveyed by the existence of a lag at the more easterly 

 stati ns, this in no way affects the possibility of prevision as long 

 as the lag remains fairly constant. I am therefore of opinion 

 that in regard to this question the evit^ence furnished by Mr. 

 Chambers is exceedingly valuable, and that so ,long as districts 

 are only taken into account that lie within the tropics, such as 

 Southern India, the possibility of prevising famines by noting 

 the occurrence of barometric maxima at mire westerly stations 

 may in time be accomi)lished. For Northern India, and pro- 

 bably other similar sub-tropical regions, the matter is at present 

 more cmpUcated. E. Douglas Archibald 



P.S. — In the preceding letter I have only dwelt upon the 

 limitation to be applied to Mr. Chambers's conclusions in the 

 case of Northern India. It is obvious however that there are at 

 least two distinct difficulties to be explained, before they can be 

 finally accepted, even for countries within the Tropics, viz. (i) 

 Why the barometric waves should commence on one meridian 

 rather than on another, and (2) if, as Mr. Chambers thinks, the 

 waves of pressure travel slowly round the earth, why they do 

 not reappear at the place where they started after an interval of 

 about one year and eight months (calculated from the lags given 

 in Mr. Chambers's paper). At present tliere does not appear to 

 be the slightest evidence to show that they reappear at all, and 

 if they do not, when and where do they disai)pear ? — E. D. A. 



Mr. E. D. Archibald states in his friendly criticism of my 

 paper on "Abnormal Variations of Barometric Pressure in the 

 Tropics, and their Relations to Sunspots, Rainfall, and 

 Famines," that the occurrence of a decided lag in the baro- 

 metric movements at easterly, as compared with westerly 



stations, could only be utilised to previse famines if we knew 

 for certain that famines in those districts to which the method is 

 applied invarialjly took their rise from one set of conditions, 

 such as failure of the usual summer rains, preceded and accom- 

 panied by high barometric pressure. It appears to me, how- 

 ever, that if the variations of the rainfall can be' definitely related 

 in any manner to the corresponding variations of the barometric 

 pressure, there is no necessity for such a limitation. If, for 

 instance, in Northern India, " a heavy winter rainfall generally 

 coincides with a high barometric pressure, and vice versa," as 

 Mr. Archibald seems prepared to admit, then the occurrence in 

 the -diinter of a high pressure «ould portend a heavy winter rain- 

 fall, and vice versA, and in this case the failure of the winter 

 rains might be foreseen by observing the progress eastward of 

 the barometric minima. 



But I am not aware that the relation above mentioned between 

 tlie barometric pressure and the winter rainfall of Northern India 

 has yet been worked out with sufficient definiteness for the pur- 

 pose in view, for although there does appear to be some evi 

 dence in favour of that relation when the average pressure and 

 the total rainfall of the whole winter are taken into account, yet 

 on the other hand it is now known that the short rainy periods 

 of the winter ai'e periods of relatively Iffiu pressure. It is not 

 improbable that these periods of low pressure, and the rainfall 

 which accompanies them, are connected with the feeble cyclonic 

 disturbances which (as appears from the charts of storm- 

 tracks published by the American Government) occasionally 

 enter the north-west of India in the winter months and travel 

 down the Ganges Valley sometim s as far as Bengal. The facts 

 concerning these winter rains seem to accord far lietter with this 

 view of their origin than with the old notion of their connection 

 with the upper anti-monsoon current, an idea wliich I observe 

 has now been abandoned by Mr. Blanford, the Meteorological 

 Reporter to tlie Government of India, although up to a recent 

 date it was still retained by some other Indian meteorologists. 

 The question is as yet involved in much obscurity, and I must, 

 with the above suggestion, leave it to be dealt with by those 

 more immediately concerned. 



But whatever the relation between the w inter rainfall and the 

 barometric pressure may be, I cannot help thinking that Mr. 

 Archibald attaches an exaggerated relative importance to these 

 winter rains, for, from the register of Allahabad, the capital of 

 the province, it appears that the winter rain amounts on the 

 average to only I '54", whereas the average summer rain amounts 

 to 36'84". And similarly at Delhi, the average total winter rain 

 is only 3'0i", while that of the summer is no less than 24'6o". 

 Such being the case, I think it would be difficult ht prove that 

 "the famine of 1S60-61 in the North-West Provinces was 

 mainly due to the absence of the winter rain," more e-pecially as 

 the summer rain of 1S60 in that province w.is deficient to the 

 extent of nearly one-half, the fall having amounted to only 54 

 per cent, of the average. 



Neither does it seem clear why the methods of forecasting the 

 general character of a coming season, which are suggested in my 

 paper, should of necessity be applicable only to intertropical 

 regions. It is true that I have dealt only w ith barometric data 

 furnished by stations lying within the tropics, but my only reason 

 for doing so was that there seemed a better prospect of obtaining 

 ilefinite results from the records of tropical stations, where the 

 weather is generally of a comparatively settled character, than 

 from those of stations situated in extra-tropical regions, where 

 the weather is generally more disturbed. Indeed I am rot 

 without hope that the results I have obtained will induce 

 IJuropean meteorologists to take up the subject with a view to 

 the possibility of prevising the general character of coming 

 seasons in Europe from observations recorded in America. 



Fred. Chambers 



STANDARD THERMOMETERS 



"TJEAR SIR, — The Kew Committee have instructed me to 

 forward you the enclosed Memorandum on Standard 

 Thermometers, and to request on their behalf that you would be 

 so good as to publish it in Nature if you consider it suitable 

 for insertion. G. M. Whipple 



Kew Observatory, Richmond, Surrey, February 9 



Dr. Leonard Waldo has recently communicated to the 

 American /onrna! of Science an ai-ticle entitled "Papers on 

 Thermometry from the Winchester Observatory of Vale College." 



