154 



NATURE 



[March 31, 1921 



The Origin of the South-west Monsoon.^ 



By Dr. G. C. Simpson, F.R.S. 



IT has generally been held that the south-west 

 monsoon owes its origin to the great difference 

 of temperature which exists during the summer 

 months between the heated land surface of India and 

 the surrounding oceans, the general idea being that 

 the warm air over the land rises, and damp air from 

 the sea flows into India to take its place, thus result- 

 ing in the strong south-west winds, the rainfall itself 

 being due to the cooling of the air as it rises over 

 India. 



This theory has to face the difficulties that the tem- 

 perature over India is much higher in May, before the 

 monsoon sets in, than it is during the monsoon itself ; 

 that the temperature is higher in years of bad mon- 

 soon than in years of good monsoon ; and that the 

 part of India which has the highest temperature and 

 the lowest pressure, and where ascending currents 

 should be the greatest, is a region of practically no 

 rainfall throughout the monsoon. 



The true explanation of the south-west monsoon 

 can be obtained only by taking a wide view of the 

 weather conditions over large parts of the earth's 

 surface during the summer months in the northern 

 hemisphere. It is then seen that the south-west 

 winds are not due to the temperature in India, but 

 are a relatively small part of a general circulation of 



1 Abstract of a paper entitled "The South-west Monsoon," read to the 

 Royal Meteorological Society on Wednesday, March i6. 



the atmosphere caused by a region of high pressure 

 over the South Indian Ocean and a region of low 

 pressure which extends over the whole of Central 

 Asia. Air passes northwards from the region of high 

 pressure as the south-west trade winds so far as the 

 equator, where it gets caught up in the circulation 

 around the low pressure over Asia. On account of 

 the particular arrangement of sea and land, combined' 

 with deflection of wind currents due to the earth's 

 rotation, this air travels for 4000 miles over the sea 

 before it reaches India, where it arrives in a very 

 warm and exceedingly humid condition. This air, how- 

 ever, would probably sweep right across India to its 

 goal in Central Asia without producing much rainfall 

 if it were not for the unique distribution of moun- 

 tains around India. From the north of the Mokran 

 coast, right round India, following the line of 

 Afghanistan, the Himalayas, and the mountains of 

 Burma, there extends an unbroken wall of moun- 

 tains, nowhere lower than 5000 ft., standing directly 

 athwart the air-currents. The mountains catch the 

 air, which is being driven by a pressure distribution 

 extending from the Southern Indian Ocean to the 

 centre of Asia, in a kind of trap, out of which there 

 is no escape except by ascension. The damp, humid 

 air. which begins to rain as soon as it rises 500 ft., 

 is forced to rise between 10,000 ft. and 20,000 ft., and, 

 in consequence, large masses of water are precipitated 

 over the greater part of the Indian area. 



The Finsbury School of Chemistry. 



By Prof. G. T. MoRC-iN, F.R.S. 



THE widespread feeling among scientific workers 

 that the threatened closing of the Finsbury 

 Technical College would be a calamity of national im- 

 portance has found expression in a petition recently pre- 

 sented to the council of the City and Guilds of London 

 Institute. In this appeal, which is supported by a 

 long list of eminent names representative of every 

 branch of art, science, and technology,, the members 

 of the Finsbury Technical College Defence Committee, 

 many of whom are former students of the college, 

 testify to their grateful appreciation of the long- 

 continued benefactions made by the institute to the 

 college, and urge the council to take into considera- 

 tion all possible sources of assistance in the responsible 

 task of keeping the college open as an institution for 

 higher technical education. 



The salving of Finsbury cannot be regarded other- 

 wise than as a prudent step in the conservation of our 

 educational resources at a time when public expendi- 

 ture on new institutes embodying untried schemes is 

 scarcely likely to meet with popular approval. This 

 anticipated continuance of the college involves, how- 

 ever, a retention in its entirety of the unique system of 

 scientific education given at Finsbury, so that the 

 future of this institution may be a logical and evolu- 

 tionary development of its former activities. The 

 policv consistently adopted in the past by the City 

 and Guilds of London Institute was to place implicit 

 trust in the judgment of the scientific men appointed 

 to the professoriate of the college. These professors 

 were not tied down by formal curricula, and were 

 allowed complete liberty to teach their respective sub- 

 jects in their own way. 



It is lar^elv this freedom from prescribed courses 

 and examinational restraints which has given to the 



NO. 



2683, VOL. 107] 



Finsbury School of Chemistry, founded by Prof. H. E. 

 Armstrong in 1879, its outstanding and distinctive 

 features. From the first its laboratories were a centre of 

 unceasing chemical activity, for they were open to day 

 and ev^ening students, who found unfailing assistance 

 in their preparatory studies and inspiration in research 

 from the hard-working staff whom the professor 

 gathered round him. Among the more salient inves- 

 tigations of the early Finsbury School of Chemistry, 

 which inaugurated a new era in the teaching of this 

 science, were the researches on the laws of substitu- 

 tion among aromatic compounds and on the relation- 

 ship between colour and chemical constitution, and 

 the important discovery by Armstrong and Miller of 

 the purification of coal-tar hydrocarbons through their 

 sulphonic acids. 



With Prof. Meldola's arrival in 1885 the chemical 

 department was brought into even closer association 

 with the synthetic colour industry. The new professor 

 had recently discovered the oxazine blue which still 

 bears his name, and had also made in the works 

 several notable discoveries which afterwards bore fruit 

 either in this countrv or abroad. The investigations 

 then initiated at Finsburv showed the influence of the 

 earlier industrial experience of its director. The 

 course of substitution in the naphthalene series was 

 the subject of several memoirs, and the researches on 

 azo-compounds originally commenced in the works 

 laboratory were continued throughout the remainder 

 of the professor's lifetime. In collaboration with 

 Mr. F. W. Streatfeild, Meldola instituted an inquiry 

 into the constitution of diazoamino-compounds and 

 amino-amidines which brought to light unexpected in- 

 stances of isomerism. In looo he discovered the first 

 recorded instance of the replacement of a nitro-group 



