430 



NATURE 



[June 3, 192c 



which are capable of operating under a variation 

 of head equal to 50 per cent, on each side of the 

 mean, with efficiencies which do not fall below 

 70 per cent, over this range, and with reasonably 

 high speeds of rotation under the heads available. 



Even with such turbines, the number of 

 technical problems to be solved before a tidal 

 scheme of any magnitude cap be embarked upon 

 with confidence is large. The questions of single- 

 'versus double-way operation, of storage, of the 

 effect of sudden changes of water-level due to 

 strong winds, of wave effects, of silting in the 

 tidal basin and of scour on the down-stream side 

 of the sluices, of the best form of turbine and of 

 generator, and of their regulation and of that of 

 the sluice-gates, are probably the most important, 

 though not the only, subjects to consider. 



On^ the other hand, the possibilities of tidal 

 power, if it can be developed commercially, are 

 very great. Assuming a mean tidal range of only 

 20 ft. at springs, and 10 ft. at neaps, and adopt- 

 ing the single-basin method of development with 



operation on both rising and falling tides, each 

 square mile of basin area would be capable, with- 

 out storage, of giving an average daily output 

 of approximately 110,000 horse-power-hours. In 

 such an estuary as the Severn, where an area of 

 20 square miles could readily be utilised with a 

 spring tidal range of 42 ft., the average daily, 

 output, without storage, would be approximately 

 10,000,000 horse-power-hours. 



At the present time it is difficult to obtain an 

 even rough estimate of the total cost of such a 

 scheme, owing to the uncertainty regarding many 

 of the factors involved. The whole question 

 would appear to merit investigation, espe- 

 cially on matters of detail, by a technical committee 

 with funds available for experimental work. As 

 a result of such an investigation, it is at least 

 possible that a definite working scheme could be 

 formulated capable of generating power at a cost 

 at least as small as, and possibly much smaller 

 than, that of power generated from any coal-fired 

 installation. 



Obituary. 



Prof. C. A. Timiriazeff, For.Mem.R.S. 

 'T'HE death is announced of Clement Arkadie- 



vitch Timiriazeff, emeritus professor of botany 

 in the University of Moscow. Timiriazeff was the 

 only Russian botanist who was at all a familiar 

 figure in England. In earlier days he came to 

 England and saw Charles Darwin, while his last 

 visit was made as a delegate to the Darwin cele- 

 bration in Cambridge in 1909. His earliest pub- 

 lication appeared in 1863 — a Russian book on 

 "Darwin and his Theory," which ran through five 

 editions. Here he made his mark as an attractive 

 expounder of science for the general reader, and he 

 followed this work with books on "The General 

 Problems of Modern Science," "Agriculture and 

 Plant Physiology," and "The Life of the Plant." 

 The last was in great demand, there being seven 

 Russian editions between 1878 and 1908, while in 

 1912 it was translated into English, and is widely 

 read to the present day. Its characteristic note is 

 an exposition of plant structure and function based 

 on the chemical and physical processes at work in 

 the living plant. Without comparison of the early 

 editions we cannot tell at what date this book took 

 the form in which it appeared in English, but it 

 looks as if Timiriazeff was one of the earliest 

 writers to take up this essentially modern outlook. 

 His attitude was no doubt an expression of his 

 early training under chemists and physicists. Born 

 in 1843, he studied under Bunsen, Kirchhoff, 

 Helmholtz, and Berthelot before working with 

 Boussingault. 



Timiriazeff made himself famous by work on 

 one single problem — the participation of the dif- 

 ferent rays of the visible spectrum in the photo- 

 synthetic activity of the green leaf. The tech- 

 nique which he brought to the attack on this 

 problem seems almost an exact expression of the 

 NO. 2640, VOL. 105] 



combined influence of his teachers : good methods 

 of gas-analysis, pure spectral illumination, and 

 experimentation on isolated leaves ; combined with 

 the sound conception that rays utilised for work in 

 the chloroplast must be rays abundantly absorbed 

 by the pigment chlorophyll. Working with a 

 micro-eudiometer, concentrated sunlight, and a 

 narrow spectroscope slit, he was able to disprove 

 the accepted view that the yellow region, which 

 is so bright to the eye, is the most effective region 

 of the solar spectrum, and to locate the efficiency 

 in the red region where absorption by chlorophyll 

 is greater. Afterwards he demonstrated the 

 secondary maximum of photosynthetic effect in the 

 blue region, where also absorption is great. 



This work was published in different forms, at 

 various dates, in scientific journals of most Euro- 

 pean countries, the final presentation being the 

 Croonian lecture to the Royal Society in 1903. The 

 actual experimental work seems to have been all 

 done between 1868 and 1883. There is no evi- 

 dence that he published research work on any 

 other subject, so that we have in Timiriazeff the 

 remarkable case of a man who, having achieved 

 fame by one important line of research at forty, 

 was content to devote the remaining half of his 

 life to teaching and exposition. 



j The announcement of a new book, "A Nation's 

 Heritage," by Hardwicke Drummond Rawnslev, 

 I sadly coincides with the record of its author's 

 I death. Born on September 28, 1851, the distin- 

 { guished canon died on May 28, to the last pur- 

 i suing the self-imposed task of persuading his 

 I fellow-countrymen to take care of their own 

 treasures. His mother was a niece of Sir John 

 j Franklin, the Arctic explorer. In education Canon 

 1 Rawnsley had the good fortune to be at Upping- 



