May 8, 1919] 



NATURE 



193 



minations of nitrogen and dry matter in 227 samples 

 of ten varieties collected from sixty-five growers in 

 eighteen English, seven Welsh, six Scottish, and 

 twenty-three Irish counties. In addition to these, 

 twenty •"miscellaneous" samples were received and 

 analysed. The report gives much valuable informa- 

 tion as to the average composition of the potatoes 

 grown in the United Kingdom, and discusses the 

 variations in composition due to such causes as 

 climate, soil, manuring, and size of tuber. The com- 

 position of different varieties and of different groups 

 of varieties is also compared. Further work on many 

 of these points is in progress. Perhaps the most 

 important point raised by the issue of this report is 

 the need for accurate information as to the composi- 

 tion of almost all home-grown foods. When the 

 Royal Society Food (War) Committee was engaged in 

 making its survey of the food supplies of the nation 

 (Cd. 8421), one of the chief difficulties was the dearth 

 of accurate systematic analyses of all kinds of home- 

 grown foods, and the committee was forced to rely 

 for the most part on American figures, which may not 

 accurately express the composition of British-grown 

 products. The report in question removes this diffi- 

 culty for British-grown potatoes. It is to be hoped that 

 reports on similar lines may follow dealing with other 

 home-grown foods, but, unfortunately, work of this 

 kind does not appear to be anybody's business. It is 

 high time some organisation was set up to maintain 

 on a permanent basis the survey of the food resources 

 of the nation initiated by the Food (War) Committee 

 of the Royal Society. 



I\ the March issue of Terrestrial Magnetism and 

 Atmospheric Electricity Dr. L. A. Bauer and Messrs. 

 H. W. Fisk and S. J. Mauchly complete their 

 examination of the magnetic observations taken 

 during the solar eclipse of June 8, 1918, and come to 

 conclusions which may be summarised as follows : — 

 Appreciable effects were observed during the eclipse 

 at all stations within the zone of visibility, and war- 

 rant the statement that a solar eclipse causes a varia- 

 tion of the earth's magnetic field. The magnitude of 

 the variation is from a tenth to a fifth of the solar 

 diurnal variation of the element on a normal day. Its 

 direction is, in general, opposite to that of the daylight 

 portion of the solar diurnal change. The effects are 

 seriously modified bv the altitude of the observing 

 station. 



Particulars of a large oil-fuel reservoir at Rosyth 

 are given in the Engineer for April 4. The reservoir 

 is in two sections, having a combined capacity of 

 60,000,000 gallons, and is constructed of concrete on 

 a rock foundation. The retaining walls have an 

 average height of 3:; ft., and are reinforced with steel 

 rods; each wall is in sections ranging from 54 ft. to 

 58 ft. in length, with expansion joints between. The 

 concrete floor has a minimum thickness of 2 ft. q in., 

 and the reservoir is covered with the roofing system 

 known as the Belfast lattice-timber truss, with spans 

 of i,o ft. Every precaution to secure oil-tightness was 

 observed in the construction, with satisfactorv results 

 in the finished structure. The complete work occupies 

 iij acres, and the roof area is 7^ acres. 



The Times Engineering Supplement for April con- 

 tains an article by Sir George Greenhill on geometrical 

 and mechanical fit. The principles of geometrical fit 

 were enunciated fifty vears ago in the first edition 

 of Thomson and Tait's "Natural Philosophy," but 

 the message therein does not appear to have reached 

 the mechanical engineer yet. The method of firoduc-' 

 ing a geometrical rifle-rest described in Thomson and 

 Tait appears to be too simple and subtle for the 

 official mind to grasp, so the old-fashioned sealed 

 NO. 2584, VOL. 103] 



pattern manifold point-rest is still at work, destitute 

 of scientific theory, working against an excessive 

 number of spring supports, and the rifle never return- 

 ing exactly to the same position. It will be conceded 

 by most people who have had business relations with 

 instrument-makers that the principles of geometrical 

 fits are still not generally understood. This is due, 

 in part at any rate, to the conservative class of work- 

 men employed. Sir George mentions the Cambridge 

 Scientific Instrument Co. as using the geometrical fit 

 principle, and might have added also the name of the 

 firm of Barr and Stroud. There is no finer example 

 of what can be done by geometrical appliances than 

 the range-finder made by this firm. 



^ An illustrated account of a pulverised-fuel locomo- 

 tive appears in the Engineer for April 25. The ap- 

 pliance has been invented by Mr. J. G. Robinson, 

 chief mechanical engineer of "the Great Central Rail- 

 way, and, owing to the success already obtained, one 

 of the large 2-8-0 engines is under construction with 

 this apparatus. Up to the present the fuel employed 

 consists of the settlings from the exhaust of the fans 

 over the screening apparatus of the collieries, and 

 has not received any treatment with the view of 

 increasing its fineness, which is such that 80 p>er cent, 

 will pass through a screen of 200 meshes per lineal 

 inch; the ash content is about 10 per cent. Before 

 being placed in the tender the fuel is dried by being 

 stored for a few days over the flues of a battery of 

 boilers. Considerable alterations have to be made 

 in the internal arrangements of the fire-box in order 

 to adapt it for burning pulverised fuel. The fuel is 

 contained in a hopper in the tender, and fed to the 

 furnace by conveyer screws driven by a small engine. 

 On leaving the conveyers the fuel is met by a blast of 

 air supplied by a fan driven by a de Laval steam 

 turbine, and is led through pipes to the furnace. It 

 would appear that this system of firing locomotives 

 is at last attaining to a practical solution in this 

 country as in America. 



The second report issued by the Conjoint Board of 

 Scientific Societies states that the number of con- 

 stituent societies is now fifty-four, and a list of these 

 bodies, together with the names of their representa- 

 tive, is presented. A summary is given of the work 

 of the various committees dealing respectivelv with 

 (i) the Catalogue of Scientific Literature, (2) the 

 application of science to agriculture, (3) national 

 instruction in technical optics, (4) education, (5) the 

 prevention of overlapping among scientific societies, 

 (6) the metric system, (7) anthropological survey, 

 (8) iron-ore, (9) water-power in the British Empire, 

 (10) timber for aeroplane construction, (11) glue and 

 other adhesives, (12) joint buildings for technical 

 societies, (13) the foundation of a geophysical institute, 

 (14) oxides and silicates, and (15) patent laws. The 

 report issued by Committee No. i is at present con- 

 fidential. No. 2 is considering the design, construc- 

 tion, and testing of electrical tractors and other agri- 

 cultural machines. The committee dealing with 

 education directs attention in a report on Civil Ser- 

 vice examinations to the undesirable tendency to en- 

 courage mathematical studies to the detriment of other 

 scientific subjects. In dealing with the scientific needs 

 of the Civil Service the preponderance of appoint- 

 rnents carr\'ing literary rather than scientific qualifica- 

 tions demands attention, and as appointments are 

 at present made largelv by nominations, suitable men 

 with scientific knowledge should be selected for appro- 

 priate administrative posts. The report issued on 

 water-power in the British Empire has already been 

 mentioned in these columns, and useful work has 

 also been done in regard to the supply of timber for 

 aeroplanes, glue, p?per, etc. The foundation of a 



