March 3, 1892] 



NATURE 



413 



Government and Academy of Sciences commissioned 

 him to go to America, the object being that he should 

 describe the natural productions of that part of the 

 world, and introduce into Sweden any useful North 

 American plants which might be expected to thrive in 

 Northern Europe. Kalm reached England in February 

 1748, and remained there until August, when he started 

 for America. On his way back, in 1751, he visited this 

 country again, staying about a month. An account of 

 a portion of his travels he afterwards published in three 

 volumes. The part relating to America was translated 

 into English in the eighteenth century by J. Reinhold 

 Forster, but the author's account of England appears 

 now in English for the first time. The work is full of 

 interest, and was well worth translating. Kalm first 

 records his impressions of London and suburbs, and 

 then takes us successively to Woodford, Little Gaddes- 

 den, and Gravesend, each of which is made a centre for 

 a number of observations, chiefly in connection with 

 agriculture. To students of the history of agricultural 

 methods the work will be invaluable; but it will also give 

 pleasure to readers with a less serious purpose, for it 

 •contains suggestive references to many aspects of Eng- 

 lish life, and the author always writes accurately and 

 with good taste. The translator has accomplished his 

 task with great spirit and intelligence. 



LETTERS TO THE EDITOR. 



[TAe Editor does not hold himself responsible for opinions ex- 

 pressed by his correspondents. Neither can he undertake 

 to return, or to correspond with the writers of, rejected 

 manuscripts intended for this or any other part of ^ATiJKt.. 

 No notice is taken of anonymous communications. ] 



The University of London. 



It is always a pleasure to read Mr. Thiselton-Dyer's expres- 

 sions of opinion oa University organization, I have before 

 now joined my word to his in condenanalion of Sir George 

 Young's proposed " Albert " or " Gresham " Charter. Never- 

 theless, I must beg you to grant me space to point out some 

 inaccuracies in Mr. Dyer's letter in your columns of February 

 25 (p. 392), the purpose of which seems to be to give reason for 

 distrusting, or, at any rate, treating with little confidence, Uni- 

 versity organizations on the German or professorial model. 



Mr. Dyer rightly enough appeals to his own early experience 

 as a teacher and student. It is therefore fair to point out that 

 this experience does not include a German University, and that 

 the conception of it sketched by him, and of a professor's rela- 

 tions to his pupils therein, is entirely erroneous. Mr. Dyer 

 •cannot free his mind of the University of London tradition. 

 He regards the German as well as all Universities as organiza- 

 tions for bringing candidates up to a certain pitch of examina- 

 tion-room performance. This is not what a German University 

 attempts. The measure of its success is not what Mr. Dyer 

 would suggest, but is found in the contributions to science, the 

 new knowledge created by the professor and his students, and 

 in the spread of a love for producing such new knowledge. 

 Mr. Dyer attributes to Lord Sherbrooke a strange saying — 

 namely, that professors who examine their own students are 

 comparable to "tradesmen who sample their own goods." I 

 can hardly credit that Lord Sherbrooke ever said anything so 

 unmeaning. We have all heard the professor-examiner com- 

 pared to " a merchant who brands his own herrings " — but this 

 "sampling of his own goods" is a new charge. 



Lastly, I must point out that Mr. Dyer, by inadvertence, 

 attributes to me a statement, or rather assent to a statement, 

 before the Royal Commission on the proposed new University 

 for London, which had exactly the opposite significance to that 

 which he gives to it. Mr. Dyer says that I admitted to Sir 

 William Thomson that " a teacher may, with judiciousness of 

 course, and with common-sense in his teaching, teach the best 

 that he knows" under the present University of London 

 system. I am glad to note that Mr. Dyer has looked at the 

 Blue-book. But if he had read more carefully he would have 

 seen that Question 662, by Sir William Thomson, was, " Can an 

 examiner under the London system ask the best that he 



NO. II 66, VOL. 45] 



knows ? " and that my answer was, " Probably not." Then Sir 

 William continued (Question 663) : " But, on the other hand, 

 a teacher may, with judiciousness, &c., teach the best that he 

 knows? ' to which I answered, "Yes." Then said Sir William 

 (Question 664), " If he is examining his own pupils he may bring 

 into the examination something of the best and the newest ? " to 

 which I replied, "Certainly." 



It is clear enough that Sir William Thomson's proposition, 

 to which I assented, was that, under the London system of 

 external examiners, an examiner cannot put questions involving 

 the best and newest ; yet a teacher may and should teach the 

 best and newest ; and if, contrary to the principle of the L >ndon 

 system, the examiner is the teacher, he can introduce with judg- 

 ment into the examination this element of the best and newest. 



Mr. Dyer has not, it seems to me, yet mastered the dis- 

 tinctive features of the German or professorial University 

 system, and is, therefore, not a trustworthy guide as to its 

 advantages and disadvantages. E. Ray Lankester. 



Superheated Steam. 

 A COMMUNICATION froui Lord Rayleigh, under the above 

 heading, in Nature of P^ebruary 18 (p. 375), draws attention 

 to a misunderstanding which has been pointed out by me on 

 every occasion in the last twelve years when I have been ex- 

 plaining the thetaphi diagram in public, saying that " only the 

 heat which superheated had its efficiency increased, according to 

 the temperatures at which its respective portions were imparted 

 to the working substance." Mr. Willans has also been dissemi- 

 nating correct views regarding this point amongst those who 

 visit his engine-testing laboratory. The diagram given by me 

 in my paper on ihetaphi, in 1880, makes this very plain. 



The vertical ordinates here are absolute temperatures, and the 

 area is heat or energy. Without superheating, Caruoi's law 

 gives, between temperatures A and B — 



F = ^ = ^°^^ = ^ 



H Heat M + N* 



Superheating to temperature S, the same law gives — 



F - ^^ = ^Q*"^ = N J-J^J- R 



" H, Heat M + N-fP-fQ-fR* 

 An arithmetical expression for these quantities, practically 

 accurate, is obtained by extending the formula given in Mr. 

 Willans's paper on engine trials, at the Institution of Civil 

 Engineers — 



A = steam temperature, not superheated. 

 B — temperature of exhaust. 

 S — superheated temperature. 

 The temperatures are all absolute, and, to suit engineers, in 

 Fahrenheit measure, and the steam data of Regnault are adopted. 

 The mean specific heat for the range of superheating is taken 

 = 0*5. This will be nearly correct at high temperatures, and 

 this is strictly in accordance with my statement that the specific 

 heat of steam at low temperatures is 0*39 at constant pressure. 

 The above expressions become, without superheating, 

 A - B 



w ^ Va -^ b 



H 



E = 



fA-B I437_.7\(, 

 U+ B A ^J^ 



B) 



1437 + 'SA 



