Dec. 20,. 1888] 



NATURE 



175 



now that we have all come to recognize species as nothing more 

 than pronounced varieties, it appears to me a curiously interest- 

 ing example of the "survival " of traditional modes of thought, 

 that so many systematists still continue to regard the value of 

 Mr. Darwin's theory to consist in what is really its least im- 

 portant function. The result has been clearly displayed in the 

 present cortespondence : — 



There's su^h divinity doth hedge a species. 

 That science c.->n but peep to what i: would. 



London, December 8. 



George J. Romanes. 



Engineers versus "Professors and College Men." 

 Pkof. Tait in his recent letter says that the only meaning the 

 expression ' — conveys to his mind is the product of a mass 



by a length. \^\\^. how does he meatsure his mass and his length ? 

 I-i the mass to be measured in pounds or kilogi-ammes, or to be 

 measured in units of ^o- pounds or ,;,'• kilogrammes? And is the 

 unit of length the foot, or the metre or centimetre ? so that g is 

 v;inously ,32, 9'8i, or 981. 



These are the points which are slurred over by " Professors 

 uid College men," but are of fundamental importance to practical 

 engineers, who dare not trust to a formula till they have verified 

 it numerically. 



Let me conclude by giving Prof. Tait a question, selected from 

 College text-books : — 



What is the meaning of 





when the unit of area is one- 



'onth of an acre, the numericil value of g is 2, and the unit of 



A eight is the weight of imit volume of the standard substance 



lie substance of which the specific gravity is unity) ? " 



I think he would be amused by the variety of answers he would 



eceive, although the answers might individually be all correct. 



December 17. A. G. Green hill. 



Mr. Dodgson on Parallels. 

 Mr. Dodcson has written to me thanking me heartily for 

 my "interesting and helpful review" of his "New Theory of 

 Parallels." He admits his slip in the corollary on p. 11, and 

 supposes, as I had myself thought, .he took ADC to be the 

 triangle required instead of ABF. " But there is one criticism 

 of yours which, if true, would viiiate the whole Ireati e. May 

 1 ask you to reconsider the point, and, should you see reason so 

 to do, to notify to the readers of Nature that you withdraw 

 it? You say that, in Props, viii., xi., I tacitly assume that the 

 'amounts' of triangles are either all greater than two right 

 angles, or else all less. . . . Such an assumption would indeed 

 be monstrous." I willingly accede to Mr. 13odgson's request, 

 as the following form of his argument, supplied in his letter to 

 me, does away with my difficulty. " Either (a) there is a 

 triangle whose ' amount ' = two ri^ht angles, or ()3) there is 

 none. If (;3) be true, then either ()8i) all triangles Yizyt greater 

 'amounts,' or (^2) «// have less amounts, or (/33) some have 

 rcater amounts and all others less. Now (3i) is proved im- 

 ossible, in Prop. viii. ; (;82) is proved impossible in Prop. xi. ; 

 ,/3 3) may easily be proved impossible, by means of Prop. vii. 

 Hence (3) is impossible. Hence (o) is true." It will be well, 

 if, in a future edition, the missing link of (33) be supplied. 

 One other point puzzles Mr. Dodgson. It is my remark on 

 Prop. vi. : "How are the figures to be constructed if «>2?" 

 Mr. Dodgson says : "It surely does not need pointing out that 

 the operation of bisecting an angle may ba repeated ad libi/iim." 

 Certainly not. But what I meant was the efTect of the e bisec- 

 tions upon the resultant chords. The figures to the proposition 

 are incorrectly drawn : in the one figure BD, DC, and in the 

 other BL, P:D, DF, FC are iioi drawn greater than the radiu-, 

 and my point was not the bisections but the enlargement of the 

 figure : ihu^ if « = 3, we should have ei^ht triangles, vertices 

 at the centre \, with the sum of their angles greater than 48o\ 

 My apology for thus trespassing upon valuable space is my desire 

 to meet Mr. Dodgson's natural wish, and by pointing out what 

 I thought were faults in his " interesting " brochure to enable him 

 to make it more perfect in after editions. K. Tucker. 



University College School, 



The Porcupine Echinoidea. 

 The researches lately published by the Drs. Sarasin upon the 

 anatomy of the Echinothurida:, render a careiul reconsideration 



of the types of Aslhenosoma collected by the late Sir Wyville 

 Thomson, during the voyage of II.M.S Porcii/iim, absolutely 

 necessary in my opinion. The species were described in the Philo- 

 sophical Transactions for 1874. I shall be much obliged if in- 

 formation can be sent me regarding the whereabouts of the 

 specimens which were figured by Wild, i.e. the type-specimeni 

 of Calveria {Aslhenosoma) hystrix, Wy. Tn. ; C. {Aslhenosoma) 

 fenestrata, Wy. Td. ; ?siA. Phormosonia pi tcenta_ Wy. Th. 



P. Martin Duncan. 



Angry Birds. 



In reference to the notice of a fierce pheasant mentioned by 

 Mr. Maw in the number of Nature for December 13, I would 

 refer him to my "Observations in Natural History" (p. 172), 

 in which I have spoken of a daring cock pheasant, which 

 I saw myself, while walking in the grounds of a friend in 

 Cambridgeshire. This bird was in the habit of attacking any 

 persons that approached near the spot where he was. Some 

 woolcutters at work on the grounds had to protect their legs 

 with strong leather gaiters. L. Blomefield. 



Bath, December 18. 



Two years ago, whilst walking across a fallow field here, I 

 heard a fluttering of wings, and received a violent blow on the 

 back of the neck from a partridge : before I could recover myself 

 she strack the back of my head and knocked my hat off. 

 Although I had a heavy stick, I could not drive off the bird, who 

 made a loud noise, and now attacked me in front. As I walked 

 rapidly off, the bird followed and struck at me many times, 

 attacking my head and sh julders with the greatest determination 

 and violence. W. G. S.MITH. 



Dunstable. 



PRE SENT A TION OF A P0RTR.4IT OF 



PROFESSOR A. W. WILLIAMSON, F.R.S., 



TO UNIVERSITY COLLEGE. 



ON Wednesday (the 12th inst.) a portrait of Prof. A.W. 

 Williamson, late Professor of Chemistry to Univer- 

 sity College, London, was presented to the College by Sir 

 Henry E. Koscoe, MP., F.R.S., on behalf of the com- 

 mittee of subscribers. The portrait is painted in oil by 

 the Hon. John Collier. The presentation took place in 

 one of the lecture-rooms, the chair being taken by the 

 President of the College (Mr. John Erichsen, F.R.S.) ; 

 and amongst those present were Sir F. A. Abel, Prof. 

 Bonney, Prof. H. Morley, Dr. J. H. Gladstone, Prof. 

 George Carey Foster, Dr. Atkinson, Prof. Ramsay, Prof. 

 Thorpe, Prof. Marks, Prof. Russell Reynolds, and other 

 Professors, and a large number of the past and present 

 students of the College. 



Dr. W. J. Russell, on behalf of the Committee, for whom 

 he had acted as Treasurer, said that judging from the 

 subscription list there was a large number of the former 

 colleagues of Prof. Williamson who had subscribed to 

 this portrait ; and it would no doubt be vjry pleasant to 

 him to know that members of all the Chemical Societies 

 in England had liberally subscribed towards the portrait ; 

 and further, that many of the subscribers had not satisfied 

 themselves by sending formal contributions, but had 

 written to him (Dr. Russell) e.xpressing their great esteem 

 and regard for Dr. Williamson. The subscriptions did not 

 come only from various parts of Great Britain, but from 

 France, Ciermany, Switzerland, Italy, Russia, and even so 

 far afield as the United States, Jamaica, India, and 

 Japan. He thought this was all that it was necessary for 

 him to say in order to indicaj:e the high value which the 

 subscribers attached to the great scientific attainments 

 and labours of Dr. Williamson, whose intimate friends and 

 old pupils, those who knew him best, now came forward 

 to pay him this mark of their esteem and regard. 



Sir Henry Roscoe, ^LP., said : — I consider it, sir, a 

 privilege that, as an old pupil and an attached friend of 

 Dr. Williamson, I should have been chosen, on this 

 occasion, to present his portrait— which I think you will 



