January 5, 191 i] 



NATURE 



317 



> t the spectator with regard to the light, the colour of the 

 feathers on the back of the bird ranges from ultramarine 

 and cobalt, through green, to straw-yellow. The outer 

 layers of the feathers are transparent, and may be removed 

 without interfering with the underlying colour, which is 

 -ot due to pigment. Beneath the outer layer is a pave- 

 ment-like arrangement of polyhedral cells, the tops of 

 hich are the source of the blue colour. These caps are 

 -lightly conve.x, and when seen by reflected light are blue 

 on both sides. In the author's opinion the origin of the 

 colour may be explained by " the theory of the produc- 

 tion of blue by the reflection of light from small particles, 

 and of orange or red by the transmission of light through 

 small particles." It is, in fact, precisely analogous to the 

 colour of the air, the full blue appearing when the feathers 

 are seen by diffused reflected light, while at a low angle, 

 when the light is in part transmitted, the straw-yellow 

 results. 



A MONTHLY journal entitled Peru To-day is published to 

 give an account of Peruvian development, and from it we 

 learn that the principal cotton-producing districts are near 

 the coast, and are usually vast desert-like valleys irrigated 

 from the rivers flowing from the Andes to the Pacific. 

 Canal irrigation is adopted, and the growers have acquired 

 considerable skill in management. The sugar cultivation 

 is being improved by the introduction of labour-saving 

 devices and more modern machinerj- ; attention is also 

 being paid to drainage. The yield on well-managed 

 estates is very considerably above the average of the 

 country, a fact which indicates that there is still con- 

 siderable scope for development. An experiment station 

 has been established at Lima for working out agricultural 

 problems. 



The interesting little booklet entitled " West Indies in 

 anada," that has been drawn up -for the Canadian Exhi- 

 ; lions at Toronto and St. John's to give information about 

 the resources of the West Indies and British Guiana, will 

 appeal to a much wider audience than such publications 

 usually find. It contains a map of the West Indies and 

 tables showing their chief exports and imports ; then follows 

 an account of each island, including a short history and 

 general description, an account of the climate and sanitary 

 conditions, and of the industries. Unfamiliar crops and 

 operations such as planting bananas are illustrated. A 

 list of books dealing with the West Indies is included, and 

 finally an alphabetical list is drawn up of the products, 

 with a sufficient account of each. 



The Proceedings of the University of Durham Philo- 

 sophical Society is always an interesting volume, and the 

 current number (part v., vol. iii.) fully maintains the 

 standard set by its predecessors. Mr. Gray reports a 

 severe attack by a furniture pest, Glycyphagus domesticus, 

 de Geer, on the contents of the dining and drawing rooms 

 of a new house in Newcastle, which did so much damage 

 that all the infested furniture was destroyed. Prof. Potter 

 describes experiments showing the difference of potential 

 set up by the activity of micro-organisms in culture solu- 

 tions, and Mr. Home and Miss Coull give an account of 

 their work on the absorption of water by the seeds of 

 Vicia Faba. Engineering subjects are represented bv Mr. 

 Eden's paper on the endurance of metals under alternating 

 stresses, and Mr. Dixon's paper on torsional vibrations of 

 massive loaded shafts. 



The Board of Agriculture issues each month an excellent 

 Journal containing papers on technical subjects of import- 

 ance to farmers, market gardeners, and others, as well as 

 shorter articles and notes on crops, markets, &c. Recent 

 issues contain an article by Mr. K. J. J. Mackenzie, in 

 NO. 2149, VOL. 85] 



which he develops his well-known studies of the " points " 

 of livestock, showing how they may to some extent be 

 reduced to actual measurement, and thus become suscep- 

 tible to exact treatment. Mr. Sawyer gives an account of 

 the sugar beet grown for export in Norfolk, but considers 

 that the price offered — 17s. 6d. per ton — was barely 

 sufliicient ; he thinks that 20s. would have to be offered 

 by factories starting in England. Dr. Russell gives some 

 new analyses of seaweed, and shows that it contains 

 notable quantities of fertilising material ; unfortunately, no 

 economical method has yet been discovered of working it 

 up into a saleable manure. 



In the Bulletin of the Imperial Academy of Sciences of 

 St. Petersburg, No. 13, 1910, M. I. P. Tolmachef reports 

 the changes made in the map of the coast between the 

 rivers Khatanga and Anabar by his expedition in 1905. 

 Cape Preobrazhenie is removed more than half a degree 

 to the south. The east coast of the Khatanga Gulf was 

 found to be very irregular, jutting out into three large 

 peninsulas separated by deep inlets, and the St. Nicholas 

 Island does not exist. The entrance to Nordvik Bay faces 

 north, not west. The actual coast-line is marked in red 

 on a cutting from the loo-verst map of Asiatic Russia. 



The Memoir of the Imperial Russian Geographical 

 Society (Statistical Section, vol. x., No. 2) consists of an 

 essay by M. Semionof-of-Tian Shan, on the towns and 

 villages of Russia and their distribution in relation to 

 physical conditions and historical events. The country is 

 divided into three main divisions : the centre and north- 

 west, where agriculture thrives on the watersheds ; the 

 northern, where the climate is severe and rural industries 

 (fishing, lumbering, &c.) are pursued on the rivers and 

 lakes ; and the black soil of the south, exclusively agri- 

 cultural, where the population is concentrated in the 

 valleys. The towns are divided into groups according to 

 population and regions, and are treated in connection with 

 the non-rural industries (mining, manufacture, trade, &c.) 

 to which they chiefly owe their origin. Fifty per cent, 

 of the urban population is concentrated on the shores of 

 the Baltic. The article is accompanied by a general map 

 and many sketch-maps illustrating especial subjects. 



As the irrigation system in Egypt is continuously being 

 developed, the margin within which improvements may be 

 made becomes narrower, and factors which at first were 

 of minor importance have now to be studied. In the 

 November (1910) number of the Cairo Scientific Journal 

 Mr. J. Murray contributes a study of the seepage and 

 evaporation loss from the Ibrahimia canal, which waters the 

 greater part of Middle Egypt. A reach of 132-5 kilometres 

 is investigated, having a width of from 38 to 55 metres 

 between Deirut and Maghagha, and is treated in four 

 sections ; in these the loss is found to be 39, 2-8, 20, 

 and 08 metres per second in proceeding from Deirut down 

 stream, and a formula is proposed for reckoning the loss 

 in similar canals in Egypt. 



In the Cairo Scientific Journal for November (1910) Mr. 

 H. E. Hurst describes a visit made to some of the oases 

 in the Libyan desert when extending the magnetic survey 

 of the Nile valley to the westward. Traces of the old 

 Egyptian practice of astronomical observation were found 

 in Dakhia oasis in the method of dividing up the day 

 into periods for supplying the water from the flowing 

 wells, and in utilising the rising or setting of certain stars 

 for distributing the water to the land of different share- 

 holders in the water of the spring. The same custom 

 prevails in Baharia oasis, and also in Nubia, where the 

 water is raised from the Nile by water-wheels worked by 



