November 12, 19 14] 



NATURE 



287 



their manners, methods and creeds, is of the 

 greatest scientific value — all the greater that, as 

 civilisation advances, opportunities for the careful 

 study of these people will surely diminish. It 

 is indeed the human interest in exploration which 

 now specially calls for the attention of geo- 

 graphers, for such slight glimpses as we can get 

 into the earliest stages of human existence are 

 getting less and less. They are rapidly passing 

 away, whilst the great wide spaces of unexplored 

 world-surfaces where humanity is not, and never 

 was, can well await the geographer of the future. 



T. H. HOLDICH. 



POTASSIUM SALTS AND AGRICULTURE. 



ONE of the first results of the European War 

 was to cut off the supply of potassium salts, 

 which play a large part as fertilisers in modern 

 agriculture. Our crops of potatoes and our sup- 

 plies of milk are particularly dependent on abun- 

 dant supplies of these particular fertilisers, and 

 practically all the world's supply has hitherto 

 come from the Stassfurt deposits in Germany. 



The three crops that stand most in need of 

 potassic fertilisers are potatoes, mangolds (used 

 for dairy cows], and sugar beets. In addition, 

 two types of soil need them for other crops : 

 light sandy soils and peaty soils. Enormous 

 amounts are required in Germany, where vast 

 areas of these two types occur, and where sugar 

 beets and potatoes are largely grown ; in Sweden 

 for the same reasons ; in France .and the United 

 States for the production of sugar beets ; and in 

 this country for mangolds and potatoes. It is not 

 surprising, then, that nearly ten million metric 

 tons per annum are consumed. 



Fortunately the conditions in British farming 

 are such that potassic fertilisers are not indis- 

 pensable, at any rate for two or three years. 

 Potassium salts form insoluble combinations in 

 the soil, and do not wash out; any excess not 

 removed by the crop is therefore in safety. Fur- 

 ther, a considerable proportion of what is ab- 

 sorbed by the crop finds its way back to the soil 

 in farmyard manure, the materials sold off the 

 farm not as a rule containing much potash. The 

 supplies stored in the soil can be utilised to ad- 

 vantage by a suitable dressing of lime or chalk, 

 which displaces the potassium from its insoluble 

 combinations, and also by addition of sodium 

 chloride, which has the same effect and in addition 

 economises the consumption of potassium by the 

 plant. 



But there are sources still open to the farmer. 

 Seaweed contains considerable quantities of 

 potassium, which would become available on a 

 proper reorganisation of the kelp industry on 

 modern lines. The farm itself can also supply 

 something. At this time of the year a good deal 

 of hedge cleaning has to be done to make a clear 

 way for the plough, while later on the hedges 

 have to be cut back to keep them sufficiently low. 

 The material is very bulky, and has to be burnt 

 straight away ; it yields an ash found at Rotham- 



XO. 2350, VOL. 94] 



I sted to contain about 10 pepricent. of potash 



I (KoOj, which is thus nearly as-nch as kainit (i2'5 



per cent. K.^O). The hedges from each ten acres 



of land yield about i cwt. of ash, so that a 



300 acre farm — quite a usual size for a holding — 



could provide itself with about 30 cwts. per 



annum if all could be collected. Unfortunately 



collection is a matter of some practical difficulty 



' excepting in fine dry weather. 



! Taking all circumstances into consideration, 



1 however, it does not appear that British agricul- 



1 ture will suffer for two or three years from potash 



I starvation, though when conditions become more 



i normal the farmer will no doubt be glad enough 



i to replenish the stocks in his manure shed and his 



; soil. Up to the present it does not appear that 



I any other of the common fertilisers will be cut 



! off through the war. Indeed, the tendency is all 



I the other way, and some of the supplies usually 



j shipped to the Continent are now available for 



j use in this country. E. J. R. 



I ■ 



I NOTES. 



The anniversar}- dinner of the Royal Society, 

 i usually held on St. Andrew's Day, November 30, will 

 j not be held this year. 



! The following have been elected officers of the Cam- 

 1 bridge Philosophical Society for the ensuing session, 

 j 19 14-15 : — President : Prof. Newall. Vice-Presidents : 

 j Dr. Barnes, Prof. Seward, Dr. Shipley. Treasurer : 

 I Prof. Hobson. Secretaries : Mr. A. Wood, Mr. F. A. 

 I Potts, Mr. G. H. Hardy. New Members of the 



Council : Mr. J. A. Crowther, Mr. H. H. Brindley, 



Dr. Fenton, Mr. H. Hamshaw Thomas. 



According to the Christiania correspondent of the 

 Morning Post, a monument in the form of a monolith 

 15 ft. high has just been completed at Christiania 

 and is intended to commemorate the gallantry of the 

 late Captain Scott and his companions in their An- 

 tarctic expedition. It has been subscribed for by 

 Norwegian friends of the explorer. On the front are 

 inscribed the names of Captain Scott and those who 

 died with him, while at the back is a short record 

 of the expedition. 



A case is recorded in the daily papers of a soldier 

 who, during a recent engagement, was shot in the 

 forehead, the bullet passing out of the back of his 

 head without killing or even stunning him. He 

 remarked, " EverAthing seems green all round me." 

 When in the hospital tent he still saw even,thing 

 green, but otherwise made no complaint. This case 

 appears to favour the cerebral theory of colour vision 

 of Dr. Edridge-Green, the shock to the brain having 

 altered the discriminatory apparatus so that impulses 

 caused by green rays had a preponderating influence. 



The opening meeting of the one hundred and sixty- 

 first session of the Royal Society of Arts will be held 

 on \\'ednesday evening, November 18, when an address 

 will be delivered by Sir Thomas H. Holdich, vice- 

 president and chairman of the council. The following 

 are among the arrangements for meetings before 

 Christmas :— November 25, Sir William A. Tilden, 



