526 



NA TURE 



[March 30, 1905 



Velocity of \vind = 2-;7 kilometres per hour = 428 m. per 



minute. 

 Thermal emissivity of leaf-surface in still air = ooi5o cal. 

 Thermal emissivity (e) in air of velocity of 428 m. per 



minute = ooi5o-(-ooooi7 X 428 = 0-0577 calorie. 

 Hence mean temperature of leaf aho-oe that of surround- 

 ings =r 26=00502 2 Xoo577 = o°-43 C. 



The disposal of the incident radiant energy deduced from 

 these data is given in the next table, the total incident 

 energy R being taken at 100. 



C.^SE A. — Disposal of Incident Solar Energy by leaf <■/ 

 Helianthus annuiis. 



W 



Energy used for photosynthesis 0'66 

 ,, ,, transpiration 48'39 



W + j« Total energy expended in internal work 

 R - Ra Solar energy transmitted by leaf 

 r Energy lost by thermal emission 



■05 

 3' '40 

 19-55 



We will not consider another case in which the facilities 

 for the performance of the internal work of vaporisation 

 of water were more than sufficient to use up the w'hole 

 of the direct solar radiation absorbed by the leaf, i.e. Ra 

 was less than W-|-to. 



Such conditions are afforded by fully opened stomata, 

 high temperature, and a low degree of humidity of the 

 air. The leaves used were again those of the sunflow'er, 

 but in this case one-half of the solar radiation was inter- 

 cepted by the revolving sectors. 



C.\SE B. — Helianthus annuus. 



Solar radiation incident on leaf R ... ... =0'2746 calorie 



Coefficient of absorption, n = o'685, .". solar 



energy intercepted, Ua ... ... ... =o"l884 „ 



Water vaporised = o'00o6lS gram, .'. W, the 

 internal work of vaporisation = 0'ooo6iS x 

 5926 =0-3668 ,, 



Rate of photosynthesis = 000657 c.c. COo, 

 hence 7W, absorption of energy due to assimi- 

 lation ... .. ... ... ... ...=o"0033 ,, 



Ra = (W + ti') - r ■ 



o'iSS4 = o'3668-(-o-oo33-o'i8i7 



Velocity of wind=i2 kilometres per hour = 20o m. per 

 minute. 



Thermal emissivity of leaf-surface in air of this velocity 

 = 00 1 5 -h 200 X o-ooo 17 = 00490 calorie. 



Hence mean temperature of leaf below that of surround- 

 ings = r/2e = o-i8i7/o-0490=i°-84 C. 



Case B. — Disposal of Energy Received by Leaf from SnUn 

 Radiation and from Heat Conveyed from Surroundings. 

 R -(-)• = 100. 

 w Energy used for photosynthesis 072 

 W „ ,, transpiration So'jS 



W-t-w Total energy expended in internal work 

 R - Ra Solar energy transmitted by leai 



8110 

 18 90 



During the time at my disposal I have only been able 

 to give a brief outline of the general principles under- 

 lying an attempt to deal with the main functions of a 

 foliage leaf from the point of view of its energetics, and 

 I must refer those of my hearers who are specially in- 

 terested in the subject to the papers themselves for the 

 further elaboration of the argument and for the facts on 

 which it is based. I trust, however, that this short 

 account of the work may be sufficient to indicate that we 

 have experimental means of studying quantitatively the 

 reception of various grades of energy by a leaf, the pro- 

 portion of this which is utilised for the two main kinds of 

 internal work, and also the thermal relations of a leaf to 

 its surroundings under given conditions. 



In conclusion, I wish to anticipate a possible objection 

 which may be raised on theoi-etical grounds to some of 

 the views I have expressed. I have assumed throughout 



XO. 1848, VOL. 71] 



that the second law of thermodynamics is applicable to 

 the phenomena we have been discussing. The statement 

 of that law by Lord Kelvin limits its application to 

 " inanimate objects," and doubtless if the living elements 

 of the leaf-cells possess any power of dealing with the 

 individual molecules of the surrounding medium so as to 

 select and utilise the kinetic energy of those which are 

 moving faster than the " mean square speed," it may well 

 happen that a leaf may be able to perform some kind of 

 internal work without there being any difference of mean 

 temperature between it and its surroundings. In this 

 event the views I have put forward would doubtless require 

 some slight revision, but I think w-e may well wait until 

 this restriction of the second fundamental principle of 

 thermodynamics has received some experimental support. 



UNIVERSITY .LVD EDUCATION.\L 

 INTELLIGENCE. 



Mr. H. O. Arnold-Forster, M.P., will distribute the 

 medals, prizes, and certificates at Woolwich Polytechnic 

 on Saturday, April i. 



Dr. E. O. Lovett, professor of mathematics of Prince' 

 ton University, has been elected professor of astronomy in 

 succession to Prof. C. A. Young. 



The Prince of Wales is to visit Cardiff toward the end of 

 June, when he will lay the foundation stone of the Welsh 

 University College in Cathays Park. 



Dr. Peter Thompson has been appointed professor of 

 anatomy, and Prof. .Arthur Dendy, of the South African 

 College, Cape Town, professor of zoology, at King's 

 College, London. 



The celebration of the jubilee of the Cheltenham Ladies* 

 College and the opening by Sir Henry Roscoe of the new 

 science laboratories and lecture rooms will take place on 

 Friday and Saturday, May 12 and 13. The Marquis of 

 Londonderry, President of the Board of Education, has 

 promised to be present. 



Priv.ate munificence has provided further sums for the 

 promotion of higher education in the United States. We 

 learn from Science that by the death of Mrs. George L. 

 Littlefield, Brown University becomes the recipient of the 

 bulk of the Littlefield estate, estimated at ioo,oooJ. The 

 will provides that the corporation shall apply the money 

 as it sees fit, e.xcept that 20,000/. shall be used for the 

 establishment of the George L. Littlefield professorship 

 of .-Xmerican history. By the will of the late Mr. William 

 F. .Milton, of Ntw York, his estate w'ill go to Harvard 

 University on the death of Mrs. Milton. The daily papers 

 state that it is worth between 200,000/. and 400,000/. 

 Columbia University has received 20,000/. from Mr. Jacob 

 H. Schiflf to endow a chair of social work, and the new 

 professorship has been filled by the appointment of Dr. 

 Edward T. Devine. 



In the House of Commons on Monday Mr. Clancy asked 

 the First Lord of the Treasury whether there are any 

 requirements, statutory or otherwise, in the case of grants 

 in aid of university colleges in England, that four times 

 the amount is required from local subscriptions before any- 

 thing is derived from the public funds. In reply, the 

 Chancellor of the Exchequer said that there has been such 

 a requirement in regard to the grant in past times. But 

 proposals in regard to the future allocation of the grant 

 are now under the consideration of the Government. Mr. 

 Clancy asked whether it was not proposed that there should 

 be a grant of 100,000/. a year to the university colleges 

 mentioned in the report ; and whether there was any re- 

 quirement, statutory or otherwise, in regard to this grant. 

 The Chancellor of the Exchequer answered : There is a 

 proposal by the committee that the distribution should be 

 governed by the amount of voluntary subscriptions obtained 

 by these colleges. The (iovernment has not yet come to a 

 decision on the subject. 



At a meeting of the Association of Teachers in Technical 

 Institutes on March 25, .Mr. W. J. Lineham, chairman of 

 the association, delivered an address on technical training in 



