456 



NATURE 



[Peuruary 17, 1910 



the Zentralanstalt fiir Meteorologie und Geodvnamik 

 of Vienna. It deals with the Tyrol and Vorarlberg, 

 and has been prepared by Dr. H. v. Ficker with the 

 cooperation, in the botanical and zoolog-ical part, of 

 Prof, von Dalla Torre. The region under discussion 

 is one of special interest by reason of the great con- 

 trasts which it presents. The North Tyrol'is formed 

 by the valley of the Inn and its tributaries. Here 

 we have a long valley running east and west, and 

 protected both to north and to south by high moun- 

 tains. Fohn winds are frequent, and have a decided 

 effect in raising the mean temperature. As a result 

 many flora and fauna which are characteristic of more 

 southern latitudes manage to persist. In the South 

 Tyrol the main valleys, Etsch and Eisach, run from 

 north to south. To the north they are protected bv 

 the central Alpine range, but to the south they ar'e 

 freely open to the plain of the Po. The Pustertal, 

 running west to east, forms a region by itself. It 

 is freely exposed to winds from the east, which have 

 a decided influence in lowering the winter tempera- 

 ture. Finally, in Vorarlberg we have again a different 

 arrangement. The valleys slope down to the north- 

 west towards Lake Constance. This fact has an 

 irriportant influence on the climate, as the prevailing 

 wind over this part of Europe is from north-west. 

 The climatological data are discussed on the lines 

 suggested by Hann in his " Lehrbuch der Klimato- 

 logie," which have been followed also in the previous 

 volumes of the series. The peculiarities of each 

 region are clearly set out and contrasted with one 

 another. 



The Scholar's Book of Travel. Part i., The British 

 Isles and Readings in Physical Geographv. Pp. 

 yiii+ig7. Part ii., Europe. Pp. viii + iqS. Part 

 iii., Other Lands. Pp. viii+200. Part iv.. The 

 British Empire. Pp. viii + 200. (London : George 

 Philip and Son, Ltd., n.d.) Price 15. 3d. each. 

 Cambridge Coinitv Geographies. Cambridgeshire. 

 By Prof. T. McKenny Hughes, F.R.S., and Mary 

 C. Hughes. Pp. xiii-l-271. (Cambridge : The 

 University Press, 1909.) Price is. 6d. 

 The teaching of geography in this countrv is under- 

 going a complete change. Efforts are being made 

 in every direction to create interest in the human 

 aspects of geography and also to render the study of 

 the subject a training in the methods of science. The 

 pupil is no longer merely set to learn bv heart lists 

 of geographical data, but he is encouraged by the 

 study of maps, by simple experiments, and by refer- 

 ence to original sources, to discover and to arrange 

 facts for himself, and by his own efi'orts to arrive at 

 simple, broad geographical principles. 



"The Scholar's Book of Travel" is designed to 

 provide the young pupil with literary extracts from 

 books of travel, and to give him the opportunity of 

 learning from first hand accounts about this and 

 other countries. The four little volumes should serve 

 a distinctly useful purpose, especiallv as they will 

 probably send the learner to the excellent books from 

 which the extracts are taken. The ma.ioritv of the 

 excerpts are from the older writers-^Livingstonc, 

 Speke, Mungo Park, Defoe, Kingsley, Darwin, to 

 name a few — but the beauty and interest of the 

 passages will doubtless make the reader desire to read 

 the works of modern travellers. 



The volume dealing with Cambridgeshire follows 

 the general lines of the series to which it belongs, 

 and these have been described on previous occasions. 

 The authors provide an excellent account of an in- 

 teresting county, and readers will find that though 

 called geography the book gives particulars of the 

 geology, history, antiquities," architecture, and the 

 roll of honour of the district. 

 NO. 2103, VOL. 82] 



LETTERS TO THE EDITOR. 



[Tlte Editor does not hold himself responsible for opinions 

 expressed hy his correspondents. Neither can he undertake 

 to return, or to correspond ■with the writers of, rejected 

 manuscripts intended for this or any other part 0/ Nature. 

 No notice is taken of anonymous communications.] 



The Fertilising Influence of Sunlight. 



The past history of agricultural science furnishes several 

 examples of belated explanations of the utility of practices 

 the value of which has long become a tradition among 

 practical men. The explanation of the value of legu- 

 minous crops in agriculture is a good example. While the 

 recognition of the rdle of these crops in increasing the 

 nitrogen supply in the soil has done much to improve agri- 

 culture in new countries, it has only served to provide a 

 scientific approval of the cultural practices of ancient 

 civilisations, such as that of India, where from time 

 immemorial it has been the custom to grow leguminous 

 crops in the rotation and also as one of the constituents 

 of the mixed crops cultivated in c^iany parts of the country. 

 .Agricultural science has recently provided another ex- 

 planation of an ancient Indian practice. In the Journal 

 of Agricultural Science of October last, Drs. Russell and 

 Hutchinson have found that partial sterilisation of the soil 

 by heating or by poisons leads to an increase in the supply 

 of nitrogenous compounds and to increased fertility. These 

 investigators state that partial sterilisation of the soil kills 

 off the phagocytes which live on bacteria, and also large 

 organisms inimical in other ways to bacteria. At the same 

 time the soil bacteria are killed off, but the spores remain 

 which germinate and rapidiv multiply when the soil is 

 moistened. The new bacteria! cultures increase at an 

 enormous rate, and the resulting nitrogenous plant food 

 becomes so great that plant growth is greatly stimulated. 

 The authors then go on to state (p. 120) : — " Tliere is 

 reason to suppose therefore that the large destructive and 

 competing organisms will be found of common occurrence 

 in ordinary soils, checking the beneficial bacteria and limit- 

 ing fertility. .\n important practical problem arises ; is it 

 possible to suppress them in ordinary field soils by any 

 economical and practical process?" 



The practice among many of the best cultivators in the 

 Indo-Gangetic plain furnishes a most emphatic affirmative 

 to the above question. It has been the practice of the 

 ryots for centuries past to expose the alluvial soils of the 

 plains of India to the intense heat and light of the Indian 

 hot weather in April and Mav. The beneficial re'iult on 

 the succeeding crop is extraordinary, and has all the effect 

 of a nitrogenous manuring. It is much more than prob- 

 able that the result of this weathering is a partial sterilisa- 

 tion of the soil, and that Russell and Hutchinson's ex- 

 planation is the correct one. Except in market-garden 

 crops near the cities and in crons like sugar-cane and 

 tobacco, manures are but little used in India. The growth 

 of leguminous crops and the weathering of the soil during 

 the hot season appear to be sufficient to keep uo the 

 fertility. More nitrogenous manure would no doubt be an 

 advantage, but a great deal could be done bv the culti- 

 vators themselves in weathering the soil during the hot 

 weather in a more efficient manner than at present. 



The extended use of cheap light iron soil-inverting 

 ploughs during the hot, dry weather after the rahi harvest 

 would do much to bring about a better exoosure of the 

 soil to the sun, and a more complete sterilisation. The 

 wooden ploughs now in use are not adapted to open up the 

 heavier lands unless they are moistened bv rain, and in 

 consequence a large area of the arable land is not ploughed 

 at all until the monsoon. We consider one of the <Treatest 

 improvements possible in Indian agriculture would be to 

 impress on the rvot the value of weathering all ar.able 

 lands in .April and May to a much greater extent than is 

 done at present. When iron has taken the place of wood 

 in the ploughs of the Indo-Gangetic olain, it will be possible 

 for the cultivator to take the fullest advantage of, and 

 greatly extend, their present most admirable practice. In 

 collaboration with Mr. H. M. Leake, economic botanist 

 to the Government of the United Provinces, we have in 

 progress a series of experiments in which the practical 



