December i, 192 i] 



NATURE 



445 



report for the Colony and Protectorate. At the end 

 of the year there were 21 stations observing tempera- 

 ture and rainfall and 180 stations obser\-ing only rain, 

 making a total of 201 stations. The report mentions 

 that the principal feature of the year was the ab- 

 normal rainfall experienced generally in November 

 and December. Observations of atmospheric pres- 

 sure are given for Mombasa, Nairobi, and Londiani ; 

 the range in the different months is small. Mean 

 daily levels of Victoria Nyanza for morning and after- 

 noon are given throughout the year 1920, and the 

 a%"erage levels are given for each month and for the 

 years 1904-20. There is a sheet of diagrams at the 

 end of the report showing the normal rainfall, also 

 the rainfaH for 1920 and its difference from the normal, 

 together with curves showing the monthly rainfall 

 and the difference from the average at twent}--four 

 representative stations. Monthly average rainfall 

 tables for 126 stations are given for a number of 

 years, the period varying from twenty-nine years at 

 Mombasa and twenty-six years at Malindi to as short 

 a time as two years at some stations ; there are, 

 however, forty-seven stations with observations for 

 ten years and more. The yearly averages range from 

 95 in. at Meru.(Eyembe Mission) to as little as 7-32 in. 

 at the northern frontier (Wajir). The average 

 monthly totals are generally largest in April and May. 



Ix vol. 22 of the Special Reports on the Mineral 

 Resources of Great Britain, one of the Memoirs of 

 the Geological Survey. Mr. T. Eastwood describes 

 the lead and zinc ores of the Lake District. This 

 district, geologically considered, consists essentially 

 of Cambrian and Ordoviciain rocks belonging to the 

 Skiddaw and the Borrowdale series, interspersed with 

 a number of igneous intrusions. These rocks are 

 traversed by a number of fissure veins, in manv cases 

 accompanied also by faulting, and th^e veins have 

 given rise to the mining industn,- here described. The 

 chief gangue mineral is quartz, as might be expected 

 from the character of the country, and galena and 

 zinc blende constitute the minerals of economic value, 

 the former being often rich in silver. The author 

 gives a ver>- full account of the various mines in the 

 district dealt with, which is of great value to the 

 student of British mineral deposits. Unfortunately 

 the district is of no very great economic importance ; 

 even in. normal times ven,' few of the lodes described 

 are rich enough to form the basis of a steady mining 

 industn,'. At present, with the prevailing high price 

 of labour, the relatively low prices of the metals ex- 

 tracted, and the high cost and difficultv of transport 

 which further handicap most of them, none of these 

 mines can be worked without loss. 



The "Madruckverfahren," or machine-pressure 

 process, is a new plan for the improvement of peat, 

 so that this inferior fuel may be utilised as a sub- 

 stitute for lignite during the present coal scarcity in 

 Germany. The Exhibition of Water-power and 

 Energy in Munich opens up new perspectives by the 

 publication of research material of the Gesellschaft 

 fiir maschinelle Druckentwasserung in Uerdingen am 

 NO. 2718, VOL. 108] 



Niederrhein. The process is based on the fact that 

 the peat-colloid can be influenced if a finely divided 

 additional substance is mixed with the raw peat. The 

 material chosen is that available on the spot, namely, 

 the partially dried peat with 30 per cent, of water. 

 [ In this way a pressed product of 50 to 60 per cent, 

 water-content is produced. This mixed product 

 already shows a reduction of surface tension and a 

 flocky and crumbly condition due to the particles of 

 dr}' peat. Thenceforward the humus particles become 

 the dispersion medium and water the dispersed phase. 

 The reversibility in the earlier condition extends to 

 a certain water-content, dried turf showing an irrever.-- 

 sible alteration of condition. Ultimately the product 

 is pressed into briquettes like lignite. These state- 

 ments are extracted from an article by Heinrich Caro 

 on "Veredelung minderwertige Brennstoffe nach dem 

 Madruckverfahren " in Die Naturwissenschaften for 

 September 16. The process may be valuable to 

 Ireland, and even to England — a strange result of 

 depriving Germany of coal. 



Under the title " L'tilisons , la Houille Bleue,"' 

 Lm Nature for October 29 contains an interesting 

 article by M. H. Lemonon. illustrating a number of 

 the earlier suggestions for developing tidal power by 

 means of mechanisms operated by floats which rise 

 and fall with the tide, or by air which is compressed 

 into a suitable chamber by the rising tide. The 

 article also describes a type of paddle motor in which 

 motion of the paddles is derived from wave impact. 

 While these are of historical interest, none of the 

 methods outlined, nor indeed any such methods, are 

 capable of utilisation on a large scale, and, generally 

 speaking, their capital cost per horse-power of output 

 would be so great as to render them commercially 

 impracticable. The only hope of utilising tidal power 

 on an economic basis would appear to lie in the use 

 of tidal basins, storing water at high tide for use in 

 turbines at periods between high and low tide, and 

 in a following article the author intends to discuss 

 such methods. 



\ A DAM may be constructed across a stream for any 



I one of several purposes, such as cit}- water supply, 



improvement of navigation, hydraulic power, or flood 



I preveation. If suitably located and operated, a dam 



j primarily intended to produce the head for a power 



1 scheme may also be utilised to improve the naviga- 



I tion above the dam, to stCM-e water for equalising 



I the power output, for preventing floods, and at the 



i same time improving the dry weather flow below the 



j dam. This multiple effect cannot always be realised, 



I but there are occasions when two or more of these 



functions may profitably be combined, and in an 



article in the New Zealand Journal of Science and 



Technology, vol. 4, No. 4, for .August, 1921, Mr. A. D. 



Mead deals with the question of the most economical 



height of dam and the economic size of reser\'oir to 



satisfy the necessan.- requirements in a number of 



typical cases. 



In a paper communicated to the Section of Physio- 

 logy at a recent meeting of the British Medical Asso- 

 ciation, and briefly reproduced in the British Medical 



