228 



NA TURE 



[July 8, 1897 



pensated at the higher levels. In any case, the con- 

 clusion is irresistible that the pressure variations are due 

 to flow and not to a mere tidal rise and fall of the entire 

 atmosphere. 



A further proof that these so-called waves are con- 

 nected with the seasonal transfers of air between Asia 

 and the Indian Ocean, is the remarkable fact that the 

 pressure variations at Mauritius are exactly contrary to 

 those on the Indian plains, and in general similar to 

 those of the vertical anomalies. In other words, the 

 lower atmosphere over the Southern Indian Ocean and 

 the higher Indian air strata are analogous termini of the 

 harmonic oscillations in the general convective interflow 

 over the monsoon and trade-wind area of Southern Asia 

 and the Indian Ocean. 



The chief critical epochs of both the vertical anomaly 

 and general pressure anomaly curves observed over the 

 plains, occur in March and November. These are, there- 

 fore, the months when the character of the ensuing 

 season may be partially forecasted from an inspection of 

 the pressure curves. 



Experience has shown, as Mr. Eliot says, that " the 

 primary maximum values of these oscillations \i.e. of the 

 pressures on the plains] occur at the end of cold weather 

 |)eriods, characterised by abundant or excessive pre- 

 cipitation in Upper India and the Western Himalayas, 

 and that the primary minimum values occur near or at 

 the end of south-west monsoon periods during which the 

 rainfall has been more abundant than usual." 



If we remember that the cold weather rains occur in a 

 stratum which mostly lies above the upper stations, and 

 that the general variations above and below are almost 

 invariably opposite in character, the empirical rule 

 dimply embodies the rational fact that the maximum 

 rainfall occurs in connection with the minimum pressure 

 of the containing air-stratum. Also since the vertical 

 anomaly and plain pressure curves are inverse to each 

 other, the rule may be put thus. 



A descending vertical anomaly curve commencing about 

 November, and a descending plain pressure anomaly curve 

 •commencing about March, indicate respectively the pro- 

 bability of heavy winter and summer rainfalls. Ascending 

 •curves commencing about the same epochs indicate the 

 reverse seasonal conditions. 



In the empirical form, these relations are now being 

 successfully employed by the Indian Meteorological 

 Department in its system of seasonal forecasts. 



The marked tendency to a semi-annual or multiple 

 semi-annual variation in the general pressure anomalies 

 is curiously analogous to a similar period in cirrus bands 

 noticed by Weber, in solar and lunar halos by Tromholdt, 

 in the aurora Polaris, and in the spots and prominences 

 •on the sun. 



What causes the equally marked differences which 

 characterise the incidence of these barometric movements 

 and their attendant conditions in different years, is still a 

 mystery. Like most meteorological phenomena, they are 

 probably a resultant of several components, solar, terres- 

 trial, direct, and reactionary. 



In any case, it is evident that the general outcome of 

 these Indian meteorological researches, so far as relates 

 to the question of long-period and universal weather 

 changes, is decidedly encouraging, since it is plain that 

 the majority of the anomalies in the Indian area are 

 resoluble into harmonic periodic elements, leaving only 

 a small residual to be labelled non-periodic and unpre- 

 •dictable. The moral, therefore, is not merely to extend 

 terrestrial observation and the discussion of data over 

 wide areas on broad, rational methods, but to endeavour 

 to discover the precise way in which solar changes pro- 

 duce analogous long and short changes in terrestrial 

 weather, especially where, as in India, these relations form 

 such a dominant proportion of the total. 



Since the above was written Mr. Eliot's interesting 



NO. 1445. VOL. 56] 



article on " Periodic Variations of Rainfall in India " has 

 appeared. 



Referring as it does particularly to the remarkable 

 wave of rain and drought which has occurred during the 

 past five years, it chiefly emphasises the remark made 

 above, that the yearly anomalies in the general meteoro- 

 logical conditions are the resultant of several components 

 — local, general, terrestrial, solar, direct, and reactionary. 

 From the evidence adduced therein regarding the Indian 

 Ocean area, and a general survey of conditions which 

 have obtained in other parts of the world, it appears that 

 this large oscillation has been of world-wide incidence. 

 That it represents something in addition to the ordinary 

 variations in the oscillatory flow of the trade-monsoon 

 currents across the equator in the Indian Ocean. That it 

 is therefore due to some abnormal extra-terrestrial — 

 probably solar— influence, which must be referred to the 

 solar physicists for its solution. 



.\t the same time, its occurrence in no way invalidates 

 the preceding conclusions deduced from a study of the 

 ordinary yearly variations, or weakens the value of Mr. 

 Eliot's vertical anomaly rule, as an empirical criterion of 

 general monsoon characteristics. 



MR. NEY ELI AS. 



THE name of Mr. Ney Elias, whose death we briefly 

 announced on June 17 (p. 159), is perhaps less familiar 

 to the readers of travel and geography of to-day than it was 

 to similar students of a quarter of a century since. In 1873 

 the Council of the Royal Geographical Society awarded 

 him the Founders Medal for the successful accomplish- 

 ment of a most remarkable journey through Western 

 Mongolia. This was a district that no European had 

 traversed since the days of Marco Polo, and notwith- 

 standing the numerous difficulties which Mr. Elias over- 

 came, and the personal danger in which he often stood, 

 he was able to execute unaided a survey of the whole 

 country travelled. The distance travelled was more than 

 2000 miles, starting from Kalgan, across the desert of 

 Gobi, thence westerly to the Chinese frontier town 

 Kwei-hua, and onward in a north-westerly direction to 

 the Khangai range. The fanatical Mahommedan Mongol 

 tribes, who were at war with the Chinese garrisons, pre- 

 vented him journeying further to the south, to Kuldja, 

 which was his proposed destination. The murderous 

 devastation occasioned by this insurrection, and the im- 

 possibility of securing adequate assistance, compelled 

 him to cross the Russian frontier and seek shelter at the 

 town of Biisk. This journey, which he accomplished in 

 about six months, was not his first experience in China. 

 In 1871 he set out, with a single Chinese servant, to cross 

 the entire continent of Asia, and a few years earlier had 

 penetrated far into the interior with the view of discover- 

 ing the causes that had forced the Lower Yellow River 

 to forsake its bed and seek a new outlet to the sea. 

 According to Chinese history, this river flowing through 

 the great eastern plain of the country has had a very 

 restless and eventful career. Nine times, within Chinese 

 records, this river has varied its course, and sought a 

 fresh estuary. The positions of the various mouths are 

 scattered up and down the coast, covering, on the whole, 

 five degrees of latitude. The date of the most recent of 

 these fitful excursions is somewhat uncertain, but Mr. 

 Elias concluded, from the observations which he made in 

 1867, that the change of bed was due to continuous flood- 

 ing of the country in 185 1-2-3, by which various barriers 

 were broken down and changes of level produced. Mr. 

 Elias was subsequently employed in India, and sent to 

 Yunnan and Ladak ; also undertaking a mission to 

 Chinese Turkestan. Mr. Elias was a skilled observer in 

 many branches of physics, and in the course of his 

 travels enriched science by many observations. At 



