Oct. 27, 1881] 



NATURE 



605 



was the istue between my view of tuberculofis communicated 

 from the cow and the view which Dr. Carpenter has been ex- 

 pounding, and I hope you will have room for the passage :— 

 "The doctrine of a tuberculous virus %\as stated by Klebs in 

 1868, and has been advocated by him, as well as by Cohnheim, 

 in recent writings. In its latest form this doctrine asserts the 

 existence of a specific minute organism to whose agency the 

 infection is due. The mii,ute organism is called by Klebs Monas 

 tuberculostim. The method of proof which I have followed in 

 this work makes it impossible that the infective agency of a 

 minute organism should in any way come into my view of the 

 communication of bovine tuberculosis to man. I have rested 

 the whole case upon certain minute identities of form and struc- 

 ture in the infected body, due to the mimicry of infection. 

 Among other points there were the leaf-like and cord-like 

 outgrowths of the pleura and peritoneum, these being the 

 early stages of the lentil-like or j;earl-like nodules and their 

 connecting threads; the lymphatic glands, «uh distinct nodu- 

 lar formations in their substance ; the lungs, with smooth- 

 walled closed vomicae or v\ith encapsuled nodules. In the new 

 formations generally there vi as a particular pattern of microscopic 

 structure, in which giant cells and epithelial-like cells figure 

 largely, and there was a relatively high degree of vascularity. 

 In all these points the disease in man is a njimicry of the parent 

 disease in the bovine animal. That mimicry is not only in single 

 features, but it is of the whole disease. It is possible to conceive 

 of the juices and particles of the primarily diseased body acquir- 

 ing a kind of spermaiic virtue which gave them the power 

 to communicate the specific disease as a whole and in all its 

 several manifestations to another body in which they should 

 happen to lodge. But it is hardly possible to think of a neutral 

 living organism being chirged with the power of conveying so 

 complex details of form and structure from one body to another " 

 ("Bovine Tuberculo-is in Man," pp. 103, 4). 



25, Savile Row, W., October 24 C. Creighton 



A Kinematical Theorem 



Trof, Minchin's Theorem in Nature (vol. xxiv. p. 557) 

 may be proved easily by considering the motion as due to the 

 rolling of one closed curve on another back into its first position, 

 their lengths being of course commensurable. If you measure _>/ 

 for the rolling curve from the strsight line which forms the 

 envelope, and x along that line, then the differential of the area 

 between the envelope and the fixed curve is easily seen to be 

 ydx -f \y-dii<, where diu is the angle turned through by ihe 

 rolling curve, and is equal to ds multiplied by the sum of the 

 curvatures at the point of contact, which w e shall call a. 1 he 

 sun.mation of the former part is a multiple of the area tf (he 

 rolling curve, and therefore the same fur all lines ; that of the 

 latter is half the moment of inertia of matter distributed over its 

 perimeter with den-iiy 0-, about the line in que tion. The result 

 is therefc're the well-known property of equi-momental ellipses. 

 Similar reasoning, with the use of the property of the ce tre of 

 inertia of a system, leads to the further ro.-ult that wlien the 

 perimeter of the envelope is of constant length, the line touches 

 a circle, and different values of the constant correspond to 

 concentric circles. In the same way by a property of the centre 

 of inertia we may also prove immediately the know n theorem 

 that when the area traced out by a point is constant, the point 

 lies on a circle, and different volumes of the constant correspond 

 to concentric circles; and we may extend it to areas traced on a 

 sphere. Joseph Larmor 



54, Antrim Road, Belfast 



If Prof. Minchin will refer back to the Bullelin des Sciences 

 Jilat/iemaliques et Astronomiqiies for August, 1878, he will, I 

 think, find in a paper by M. Darboux the theorem stated by him 

 under the above title in Nature, vol. xxiv. p. 557. 



C. Leudesdorf 



Pembroke College, Oxford, October 21 



"The Dark Day" 

 Referring to the account of the phenomenon in New Eng- 

 land on September 6 last (Nature, vol. xxiv. p. 540), and in 

 Mr. Harding's letter (p. 557), let me refer your readers to a 

 succinct account of the occurrence on May 19, 1780, which 

 they will find in Webster's Dictionary, "Explanatory and 



Pronouncing Vocabulary of the Noted Names of Fiction, &c." 

 In Public Opinion (June 4, 1881) there is an account of a pre- 

 cisely similar occurrence on the morning of Sunday, NovemherS, 

 1819, known, it is remarked, as the " Phenomenon of 1819." 

 The account of this phenomenon is very explicit, and the details 

 furnished correspond so closely with the event of May 19, 17S0, 

 that a doubt might be felt whether there had been two such 

 days, or whether there had not been some mistake made in 

 regard to the date given. I wrote to Public Opinion, making 

 inquiries (see Public Opinion of June II, 1881, p. 755), but no 

 reply has hitherto appeared to my inquiries. I may observe 

 that the year 1S19 would not coincide with any one of the sun- 

 spot cycle of eleven years from 1780 to which the New York 

 Nation refers. A. Trevor Crispin 



6, Melbnry Terrace, Harewood Square, N.W., October 22 



OWENS COLLEGE SCIENCE AND 

 LITERATURE FELLOWSHIPS 



THE first award of these Fellowships, of the annual 

 value of 100/. each, which are intended to encourage 

 original investigation, was made on Friday last by the 

 Council of the 1 Jwens College. These are remarkable as 

 being the only fellowships given in any University or 

 College in the United Kingdom solely for the encourage- 

 ment of research. They are not awarded on the results 

 of examination, but after consideration of documentary or 

 other evidence. Every holder of a fellowship is expected 

 to devote his tiine to the prosecution of some special 

 study, and before the close of the year to give evidence of 

 progress by the preparation of a thesis, the delivery of a 

 lecture, or the completion of some research. He may 

 also be called upon to render some service to the College 

 either by acting as occasional examiner or by giving in- 

 struction by lectures or otherwise to the students. 



Of the thirty candidates four gentleincn were elected 

 to Fellowships. Of these one is awarded to Mr. Alfred 

 Sidgwick, 13..^. of Lincoln College, C)xford, in the De- 

 partment of Logic ; two were awarded in the Department 

 of Chemistry, namely, one to Dr. Bohnslav Brauner, of 

 the University of Prague, who has already published 

 several papers on original subjects, some from the labo- 

 ratory of the (wens College ; and a second to Mr. Harry 

 Baker, Dalton Chemical Scholar of the College, who has 

 likewise published several papers in ihe Journal oi the 

 Chemical Society. These two gentlemen will continue 

 their researches, devoting the whole of their time to 

 original. investigation. In the Department of Biology an 

 award has been made to Mr. H. Marshall Ward, B.A., 

 F.L.S., of Christ College, Cambridge, at one time a de- 

 monstrator in the Owens College, who has recently dis- 

 tinguished himself as Government cryptoga mist in Ceylon, 

 in an investigation of the cause of the coffee disease. 



THE AGE OF THE IGNEOUS ROCKS OF 

 ICELAND 

 TOURING a recent visit to the south-west part of 

 ^-^ Iceland, one or two points connected with the 

 general geological structure of the island came under my 

 observation, which I do not remember to have seen 

 noticed before, and which seem to me to be of sufficient 

 interest, to be put on record. It is well known that the 

 rocks of the island are of very different ages, some going 

 back to the Miocene per'od, while others are quite of 

 yesterday's date. It is also perhaps a general belief that 

 the volcanic forces may have continued to be more or less 

 actire from the time that the older Miocene basalts and 

 tuffs were erupted down to our own day. I doubt very- 

 much w'hether there is any evidence to justify this con- 

 clusion, and will presently mention some of the facts 

 which lead to a very strong suspicion that a prolonged 

 period of repose supervened after the accumulation of the 

 Miocene rocks, and before the eruption of the later lavas, 

 &c., had begun. The Miocene group consists of a vast 



