ii6 



NATURE 



[September 22, 192 1 



at Cambridge; Professor Vito \'olterra, one of 

 the foremost mathematicians of the day ; and' 

 Prof. R. W. Wood, of Johns Hopkins Univer- 

 sity, Baltimore, famous for his brilliant experi- 

 mental researches in optics. These outstanding- 

 representatives of science in its various branches 

 were presented to the Vice-Chancellor, Sir Alfred 

 Ewing-,iby Prof. Whittaker (acting for the Dean 

 of the Faculty of Law), who hit off the charac- 

 teristic work of each in the happiest phrasing. 



Another side issue of the British Association 

 meeting was the Royal Societies' dinner, at 

 which the fellows of the Royal Societies of Edin- 

 burgh entertained as their guests the fellows of 

 the Royal Society of London, the members of the 

 Royal" Irish Academy, and eminent foreign visitors 

 to the meeting. The Maharaj Rana of Jhalawar 

 was also a guest. This brilliant function was 

 held in the Masonic Hall, probably the most 

 artistic hall in Edinburgh. Nearly two hundred 

 were present, and the guests and hosts were 

 arranged in such a way that those repre- 

 sentative of any one science formed a group 

 at one of the tables. The toasts were pro- 

 posed and responded to by speakers selected on a 

 broad international basis, and the speeches were 



short, congratulatory, breezy, and humorous. 

 One point referred to by Sir James Dewar is 

 worth chronicling on account of its historic 

 interest, and might have found a place in 

 the handbook " Edinburgh's Place in Scientific 

 Progress." Some seventy-five years ago a young 

 extra-mural teacher. Dr. Samuel M. Brown, gave 

 four lectures on the atomic theory and, to a large 

 intellectual audience packed into his lecture room, 

 broached ideas regarding the complicated nature of 

 atomic structure which were far in advance of his 

 day, and closely approximated to the ideas now so 

 prevalent. Samuel Brown died at the age of thirty- 

 nine, and Edinburgh lost a brilliant son who, had 

 he lived, would have brought renown to his city. 



For one glorious week the people of Edinburgh 

 rejoiced in the British Association — just as pro- 

 foundly as the visiting members of the Association 

 rejoiced in Edinburgh. There was exhilaration 

 in the very air, and the profoundest problems were 

 tackled in a cheerful spirit. Two thousand seven 

 hundred and sixty-eight members drawn together 

 from all parts of the world shared in this intel- 

 lectual feast of good things, the golden memories 

 of which will be a life-long possession. 



C. G. K. 



Science and Crop Production.^ 



By E. J. Russell, D.Sc, F.R.S., Director of the Rothamsted Experimental Station. 



THE beginning of much of our scientific work 

 on crop production goes back to the year 

 1843, when Lawes and Gilbert set out to dis- 

 cover why farmyard manure is such an excellent 

 fertiliser. Two opposing explanations were 

 offered by the chemists of the day ; the older 

 view, coming down from the eighteenth century, 

 was that the fertilising value lay in the organic 

 matter ; the newer view put forward by Liebig 

 in 1840 was that it lay in the ash constituents- — 

 the potash, phosphates, etc. — left after the 

 manure is burnt, Lawes and Gilbert considered 

 that it lay in the ash constituents plus the nitro- 

 gen of the organic matter, and they devised a 

 critical field experiment to decide the matter. 

 They divided a field of wheat into plots of equal 

 size, of which one received farmyard manure at 

 the rate of 14 tons per acre, another received the 

 ashes of exactly the same dressing of farmvard 

 manure, a third received the mineral matter of 

 the ashes plus some of the combined nitrogen 

 that had been dissipated on burning, and a fourth 

 lay unmanured. The results were very striking : — 



Broadbalk ]]^heat Field, 1843. 



Farmyafd manure 



No manure 



Ashes of farmyard manure 



Mineral matter of ash plus sul- 

 phate of ammonia to supply 

 combined nitrogen .. .. 26^- 15I 



1 Abstract of a farmers' lecture of the British Association delivered at 

 Edinburgh on September 7. 



NO. 2708, VOL. 108] 



The ashes proved ineffective, but the ashes plus 

 the combined nitrogen acted just as well as farm- 

 yard manure ; it is therefore these that constitute 

 the fertilising constituents of the manure. Thus 

 the old controversy was decided in a way not 

 uncommon in science ; neither side proved to be 

 entirely correct, but both sides were found to 

 have some basis of truth. Lawes and Gilbert did 

 not rest content with this purely judicial and 

 scientific conclusion ; they saw that they could 

 make up this effective mixture of ashes and com- 

 bined nitrogen from mineral substances without 

 using farmyard manure. Even in their day 

 farmers were unable to obtain sufficient farmyard 

 manure, and it was therefore a great achievement 

 to be able to supplement the limited supplies by 

 this mixture. A factory was set up, and the 

 manufacture of the so-called artificial fertilisers 

 began. Subsequent experience showed 'that 

 the ash constituents are not all equally neces- 

 sary; in practice only two of them, potash 

 and phosphates, need be supplied in addition 

 to nitrogen. 



Chemists are rightly proud of artificial fer- 

 tilisers, for they have proved extraordinarily suc- 

 cessful in augmenting crop production all over 

 the world. The demand for them is enormous, 

 and in con.sequence prices have risen considerably 

 within the last thirty years. Agricultural chemists 

 are alwavs looking out for new substances, and 

 even during the war a new fertiliser, ammonium 

 chloride, was added to the list and new plant 

 has been erected for its manufacture. Modern 



