May 27, 1920] 



NATURE 



409 



As a preliminary, the necessary tables are given to 

 enable the manures used to be standardised to ensure 

 uniformity of treatment so far as possible, and the 

 method of noting and reporting the results is clearly 

 outlined. It is recommended that the attention of 

 farmers should be devoted to the improvement of the 

 various classes of grassland on different types of soil, 

 and particulars are given for the manuring of meadow- 

 hay, "'seeds " or rotation hay, and pastures of different 

 grades. Emphasis is laid ' on the value of liming 

 exf>eriments, which should be carried on at the same 

 time as the manurial tests. 



The attention of agricultural colleges and institutes 

 is directed to the need for various experiments other 

 than manurial trials. Grazing trials properlv carried 

 out would provide valuable information as to the best 

 methods of dealing with pasture land, and mechanical 

 operations are suggested to show the effect of mole- 

 draining, cultivation, breaking, and reseeding. In 

 addition, it is suggested that a good deal of attention 

 mi^t profitably be directed to a consideration of the 

 seeds used fof sowing down, with regard to the per- 

 manence of different varieties, the most suitable mix- 

 tures for leys and for renovating permanent grass, and 

 to the possibility of harvesting supplies of seed. 



The pamphlet is so suggestive and so broad in its 

 scope that it should find its way into the hands of all 

 interested in grassland, and it is much to be hoped 

 that the official nature of the publication will not 

 prevent it from reaching the general farming public. 



W. E. Brenchlev. 



Levelling Errors.^ 



A DEP-\RT.ME\TAL paper lately published by the 

 ■^~*- Survey of Egypt contains an interesting inves- 

 tigation of a systematic error which has been found 

 to occur in the levelling carried out in Egypt and in 

 the Sudan. The effect of this error, which has the 

 same sign over all kinds of ground, acts in the direc- 

 tion of making the backstaff reading systematically 

 too small and the forestaff reading too great. Move- 

 ment of the staves or level and other sources of 

 error having been eliminated, the author draws the 

 conclusion that the effect of refraction is not wholly 

 removed by keeping the distances between "the level 

 and the staves equal in the conditions under which 

 the work is done. Precise levelling in Egvpt is carried 

 out in the winter months and during about three hours 

 after sunrise and three hours before sunset. Experi- 

 ments have shown that at sunrise a temperature 

 lapse-rate of the order of 1° C. to 2° C. per metre 

 often exists, the air being colder near the ground than 

 higher up. In two or three hours this lapse-rate has 

 disappeared, and a little later becomes reversed, so 

 that with hotter air near the ground setting up con- 

 vection currents, unsteadiness of the staff-image sets 

 in, preventing further work. In the afternoon the 

 ground cools very slowly, so that the change in the 

 temi^erature lapse-rate, and consequently in the refrac- 

 tion, is then very gradual. 



The error is, therefore, traced to the very rapid 

 change in refraction during the early morning hours, 

 of which the effect is noticeable in observations taken 

 at a few minutes' interval. To eliminate it, all 

 staff readings are now taken with as little delav as 

 possible, and the observer reads alternately the back- 

 staff first and the forestaff first — a procedure which 

 has very materially reduced the systematic error, not 

 only in precise levellini?, but to a much greater degree 

 in second-order levelling, where the time taken 

 between successive readings is much longer. 



1 " .Svstenwtic Rrrir in Spi'it T-eveJIinjt." By J. H. Cole. Survey of 

 Egypt Departmental Paper No. 35. (Caiio, 1919.) 



NO. 2639, VOL. 105] 



It has been recognised for some time that a sys-- 

 tematic error may be caused by such a temperature 

 inversion when levelling over sloping ground, but in 

 the present report the rapid change ot the temperature 

 lapse-rate from a maximum value to zero is indicated 

 as a cause which may be expected to operate even 

 on level ground in any region where hot days follow 

 clear, cold nights with effective radiation. In the 

 last annual report of the Ordnance Survev such a 

 systematic error, almost invariablv of one' sign, is 

 referred to as being still unexplaine'd. It would seem 

 that here also local temperature inversions near the 

 ground may be concerned to some extent. 



H. G. L. 



University and Educational Intelligence. 



Birmingham. — Sir John Cadman is resigning his 

 post as professor of mining at the end of the current 

 session. 



Cambridge. — On May 19 the degree of Doctor of 

 Law honoris causa was conferred upon Lord Fly- 

 mouth, Admiral of the Fleet Lord Jellicoe, Field- 

 Marshal Lord Haig, Rear-Admiral Sir VV. R. Hall, 

 M.P., the Abbd Henri Breuil, Institute of Human 

 Palaeontology, Paris, and Sir John Sandys, Orator 

 Emeritus. 



Leeds. — At a meeting of the University Council 

 held on May 19, it was resolved that a' chair of 

 physicaj chemistrv- should be instituted, and Dr. 

 H. M. Dawson was selected to be the first occupant 

 of the chair. Since 1905 Dr. Dawson has been lec- 

 turer in physical chemistry at the University, and has 

 carried out extensive researches in various branches 

 of physical chemistry— in particular, investigations, 

 bearing on the constitution of solutions and on the 

 mechanism of chemical change. 



London. — The degree of D.Sc. (Engineering) has 

 been conferred on ^r. B. C. Laws, an external 

 student, for a thesis entitled " Elasticity and Dis- 

 tribution of Stress in Thin Steel Plates," and other 

 papers. 



From the report of the Principal Officer (Sir Cooj>er 

 Perry) for 1919-20, it appears that the University can 

 look forward to a period of unprecedented develop- 

 ment. Admissions by all channels in 1919-20 amounted 

 to 12,608, almost double the corresponding number for 

 1913-14. Candidates for first degreqs were 936, com- 

 paring with 1636, reflecting the diminished numbers 

 of those who matriculated "during the lean — the 

 honourably lean — years of the war." It is of in- 

 terest to note that of the 1086 candidates for all 

 degrees, 613 were internal and 47^ external. This 

 is gratifying evidence that the " private " student is 

 tending to disappear, or. rather, to study under more 

 favourable conditions. The list of benefactions to the 

 University and its colleges is most encouraging. The 

 outstanding gift is from the trustees of the Sir Ernest 

 Cassel Educational Trust of 150.000?.. and 4000!. a 

 year for five vears. New University chairs have been 

 established in aeronautics, modern Greek, Portu- 

 guese, Imperial historv, Dutch, bncteriologv. phy- 

 siologv, pathology, and physics. The question of 

 hostel accommodation is being considered by a soecia! 

 committee. The report concludes on "a justified note 

 of congratulation." The duty of the universities is 

 plain; their province, though extensive and varied, is 

 defined ; their wav is illuminated ; " into the univer- 

 sities the nation looks in a unique degree for hearts 

 and minds fitted to enrich the blood of the race — 

 for the constant supply of men and women of trained 

 insight and enlarged 'svmoathies, apt for the higher 

 offices of citizenship. This is our peculiar duty — to 



