550 



NATURE 



[December 22, 1921 



of the University of Leeds, and well known for his 

 work upon the nutrition of animals and milk produc- 

 tion, is director of the establishment, and takes charge 

 of the work upon animal-feeding ; Capt. Hunter, late 

 of the Department of Agriculture in Ireland, is re- 

 sponsible for the plant-breeding work ; and Capt. 

 Gimingham, who was attached to the Research Insti- 

 tute at the University of Bristol, is concerned with 

 soil problems. These heads of divisions, with twelve 

 others, constitute the research staff. 



The work set out in the report before us is neces- 

 sarily of a preliminary character. The first business 

 of a scientific establishment of this kind is to supply 

 data for the guidance of the management. The vary- 

 ing soils of the estates have to be analj'sed and cor- 

 related with the results of manurial trials in order 

 that the specific needs of each field as regards lime 

 and the inain elements of fertility can be defined. 

 Variety trials of the principal crops have to be made 

 so as to ascertain what kinds of grain and fodder 

 crops yield best under the several conditions of soil 

 and climate. Again, economic feeding rations have 

 to be worked out by trial for the particular classes of 



livestock and the special purposes for which they 

 are being kept. All this is not research, but the 

 scientific control necessary to a business organisa- 

 tion. 



Most of the present report is occupied in setting 

 out such results, which may usefully be correlated 

 with similar commercial trials, but do not present 

 any essential novelty. Research is an affair of 

 years, and wisely the director makes no pro- 

 mises and says nothing about the real investigations 

 he may have initiated. It is clear, however, that 

 new ground is being broken, particularly in connec- 

 tion with plant-breeding. The field bean, for example, 

 has been taken in hand ; on many soils it is a crop 

 of considerable economic importance, which never 

 seems to have received any serious attention from the 

 seedsmen or the older race of plant-improvers. 



The report may be obtained on application to the 

 director at the Research Station, The Bury, Offchurch, 

 Leamington. It is the first fruits of a movement of 

 great promise to agriculture, and redounds to the 

 credit of both the director and the founder of the 

 company, Mr. Joseph Watson. 



Optical Wedges. 



VX7 EDGES of tinted glass have been used for 

 ^^ graduating light for experimental purposes 

 during the last fifty years or so, and about five and 

 twenty years ago Warnerke made annular wedges of 

 pigmented gelatine. It is twenty j-ears since the 

 " Chapman Jones plate tester " was put on the 

 market, the graduated portion of which is a pig- 

 mented gelatine wedge, the mould being cut into five 

 pieces that are placed side bv side for the sake of 

 convenience. Optical wedges, therefore, have been well 

 established as standard apparatus for a long time. 



We have received from the firm of "Herlango, " of 

 Vienna (at the request of Prof. J. M. Eder) an example 

 of "a new grey wedge photometer/' called, after the 

 names of those who have devised it, the " Eder- 

 Hecht " photometer, the essential part of which is a 

 pigmented gelatine wedge with a scale printed on the 

 thin celluloid that covers its face. This, with a neatly 

 made white wood printing frame, is the complete 

 apparatus. The plate is 3 cm. by 16 cm., and the 

 divisions of the scale are 2 mm. apart. But the scale 

 is not a simple ladder. Every fifth line is numbered 

 with its mm. distance from zero, and, in addition to 

 the number, has on each side of it a short thick 

 pointed swelling to emphasise it and render it more 

 easy to see how far the light-produced image extends. 

 For use with it the firm issues various sensitive 

 papers, both printing out and development, a silver- 

 chloride paper made according to the formula of 

 Bunsen and Roscoe, and also a colour-sensitised paper. 

 An extended table gives the relative light quantity, and 

 also the "absolute light quantity in Bunsen-Roscoe 

 units," represented by each 2-mm. division. Thus, 

 given the suitable sensitive paper, the apparatus is 

 ready for use and convenient. It is applicable to light 



measurement in connection with photography, 

 meteorology, climatology, biology, light-therapeutics, 

 agriculture, the designing of buildings, botany, photo- 

 graphic reproduction processes, etc. Photometers 

 slightly varying from the above, as in steepness of 

 gradation, length of the wedge, the character and 

 coarseness of the printed scale, are provided when 

 more convenient. For photographic plate sensitometry 

 the wedge plate is 9 by 12 cm., and by the side of the 

 ladder scale are four narrow graduated strips, red, 

 yellow, green, and blue respectively. 



Accompanying the photometer is a copy of a paper by 

 Walter Hecht on the use of such photometers in plant 

 culture and a copy of a paper by Prof. Eder published 

 in the Photographischen Korrespondenz for September, 

 19 19, in which he gives apparently every possible detail 

 and formula in connection with these photometers. 

 But he does a considerable injustice to the Chapman 

 Jones plate tester in associating it with Warnerke 's 

 original step-tint sensitometer. It differs from the 

 sensitometer designed by Prof. Eder in having a wedge 

 from two to three times as long and divided into 

 twenty-five parts instead of sixty parts. These twenty- 

 five parts may be subdivided to any extent on mere 

 inspection according to the observer's acuteness of 

 vision. It has the four colours giving four definite 

 parts of the spectrum, and, in addition, an Abney 

 colour sensitometer, which shows at a glance whether 

 a plate alone or a plate plus a colour filter gives the 

 same densitv for equal brightness of several colours. 

 We think, too, that comparing the densitv produced 

 under anv given colour with a scale of densities admits 

 of greater precision than the estimation of the 

 vanishing point of the image as is done in Prof. Eder's 

 instrument. C. J. 



The South African Association for the Advancement of Science. 



Durban Meeting. 



THE nineteenth annual meeting of the South 

 African Association for the Advancement of 

 Science was held at Durban, in the Technical College, 

 on July 11-16 last, under the presidency of Prof. J. E. 

 Duerden. The meeting was well attended, and was 

 very successful. More than fifty papers were read, 



NO. 2721, VOL. 108] 



and the time-table was so arranged that attendance 

 at the presidential address of each section was possible 

 for everv member. An official welcome and a recep- 

 tion in 'the Art Gallerv was given by the Mayor of 

 Durban, while a conversazione was arranged by the 

 local committee of the association and the Natal 



