February 9, 1922] 



NATURE 



185 



fatigue through the adoption of rhythmical methods 

 of work in various industries. 



A SUGGESTION has reached us from Mr. F. J. W. 

 ;rowe, St. Peter's House, Chichester, that fine con- 

 rete might be used for making mirrors of large size 

 accurate surface such as are employed in large 

 'fleeting telescopes for astronomical work. Dr. J. VV. 

 ""rench, of the firm of Messrs. Barr and Stroud, to 

 /horn we submitted the communication, is of the 

 >inion that such a surface would not be satisfactory. 

 Jilvering shows up minute defects very plainly ; in 

 fact, rustless steel is the only material other than 

 Jiass which gives reasonably good results, and to 

 rind a plaster surface with the necessary accuracy 

 ^ould be almost impossible on account of the way 

 which • all plasters absorb water. The greatest 

 ifficulty to be met, however, is the distortion which 

 xurs when plaster sets. Both at the time of setting 

 id afterwards there are rapid crystalline changes 

 which may continue for at least one year. Any 

 plaster containing unslaked lime will undergo dis- 

 torting changes which would make the production of 

 a good optical image impossible. This defect might 

 be remedied by using a blend of cements, but, un- 

 fortunately, they are not of a kind that could be 

 worked to give a good continuous surface. 



In a report to the Mercantile Marine Department 

 of the Board of Trade on the proposed standard of 

 rejection of seamen for colour-blindness, Dr. Edridge- 

 Green states that 5 per cent, of men have diminished 

 colour perception. As there is a gradual change from 

 normal to absolute colour-blindness, it is difficult to 

 fix a point at which it shall be considered that colour- 

 blindness incapacitates a man from work as a sea- 

 man. The Nautical Advisers of the Board of Trade 

 agree that a man who can distinguish between red, 

 green, and white lights a mile distant shall be con- 

 sidered competent. Dr. Edridge-Green finds that the 

 men who fail under this test can see only three or 

 less distinct colours in the spectrum, while those 

 who pass the test see four or more. He therefore 

 fixes the line of demarcation between those who can 

 distinguish red, yellow, green, and violet and those 

 who see only red, green, and violet in the spectrum. 



The National Institute of Botany has recently 

 issued a very encouraging Second Report (1920-21). 

 During the year the headquarters at Cambridge were 

 completed and came into use, the official Seed Testing 

 Station being transferred thereto in September last. 

 Within a month a private visit was paid by their 

 Majesties the King and Queen and Princess Mary, 

 who expressed their appreciation of the importance of 

 the work carried on. In order to bring the institute 

 into closer touch with the agricultural community a 

 fellowship is being established (annual subscription 

 one guinea), in which Mr. Lloyd George has asked 

 ro be enrolled as one of the first life fellows. For 

 the welfare and progress of the work it is essential 

 that a considerable income be raised by annual dona- 

 tions and subscriptions, and it is hoped that very 

 many agriculturists will avail themselves of the oppor- 

 tunity of assisting in this by becoming fellows. In 

 NO. 2728, VOL. 109] 



the crop improvement branch, field trials of cereak 

 have been established, "preliminary trials" being 

 made to provide seeds for "full trials" which will 

 last for two years. A collection is also being made 

 of stocks of varieties of cereals, especially of historical 

 varieties of wheat, some of which are rapidly dis- 

 appearing. An interesting feature of the current year's 

 work will be an exhibition of yield trials of growing 

 cereals and potatoes on the Royal Agricultural Show 

 ground in Cambridge. At Ormskirk the immunity 

 and maturity trials of potatoes have been continued ; 

 they indicate that the system of ex{>eriment used 

 promises to lead to satisfactory results when modified 

 and extended over a longer period of time. The 

 official Seed Testing Station reports a considerable 

 increase in the year's work, in spite of the dis- 

 organisation due to the transfer from London. It is 

 proposed to hold a summer course for the training 

 of seed analysts, and a handbook of seed-testing 

 methods is in preparation. An International Con- 

 ference on Seed Testing at Copenhagen was attended 

 by representatives of the institute, and it is hoped 

 that the next conference in 1924 will be held partly 

 at Cambridge. 



In the French newspaper Savoir for December 24 

 last Prof. Capitan discusses Mr. Reid Moir's dis- 

 coveries of worked flints at the base of the Crag near 

 Ipswich and in the Forest Bed near Cromer. He 

 concludes that the simple chipping round the edges 

 of these flints is undoubtedly the work of man or one 

 of his precursors. He therefore agrees that Mr. Reid 

 Moir has found definite evidence of Pliocene man in 

 Britain. 



Sir Oliver J. Lodge will deliver the fifth Silvanus 

 Thompson memorial lecture at a special meeting of 

 the Rontgen Society to be held on Tuesday, March 21, 

 at the Institution of Electrical Engineers. 



On Thursday next, February 16, Prof. Arthur 

 Perkin will begin a course of two lectures at the Royal 

 Institution on "Dyeing: Ancient and Modern "; and 

 on Saturday, February 18, Prof. Ernest Gardner 

 will deliver the first of two lectures on " Masterpieces 

 of Greek Sculpture." The Friday evening discourse 

 on February 17 will be delivered by Prof. D. S. M. 

 Watson on "The History of the Mammalian Ear.'^' 



The annual general meeting of the Institute of 

 Metals on March 8-9 will be held at the Institution 

 of Mechanical Engineers. On the opening day of the 

 meeting the new president, Mr. L. Sumner, will 

 deliver his inaugural address, and in the evening the 

 annual dinner of the institute will be held at the 

 Trocadero Restaurant, Piccadilly Circus, W. i. Papers 

 on the constitution and properties of copper and 

 aluminium and their alloys will occupy the scientific 

 sessions of the meeting. 



In the annual report of the Physical Society to 

 be presented at the annual meeting to-morrow, 

 February 10, it is stated that Prof. A". Fowler has 

 prepared for the society a report on '* Series in Line 

 Spectra," which will shortly be issued. A second 



