January 14, 1909] 



NA TURE 



19 



age, the pedaslelled viiscs, derived, as Dr. A. J. Evans 

 has pointed out, from the Situla in vogue south of the 

 Alps about the fourth or fifth centuries B.C., deserve 

 notice. Two groups of fine Celtic sepulchral vessels found 

 at Colchester and Braintree are figured and described. The 

 second paper, by Mr. M. E. Cunnington, discusses a find 

 of fragments of Arretine ware from a late Celtic rubbish- 

 heap at Oare, in Wilts. This ware is particularl)' rare in 

 England, because just about the time when this country 

 came under Roman domination it was superseded by the 

 red-glazed Gaulish ware from the potteries established at 

 Graufesenque in the middle of the first century a.d. 



Prof. T. Levi Civita has published in the Aiii dei 

 Lined, -xvii. (2), i, a discussion of the attraction exerted 

 by a material line on points in its immediate neighbour- 

 hood. The object is to discuss, by rigorous methods of 

 modern analysis, the asymptotic forms to which the 

 potential and its derivatives tend as the point approaches 

 and ultimately lies on the line itself. The same methods 

 arc applicable, as Prof. Levi Civita shows, to the vector 

 potential of a vortex filament. This corresponding hydro- 

 dynamical problem was first discussed by Da Rios in 1906. 

 Readers of ordinary text-books will know that the ex- 

 pression for the translational velocity of a circular vortex 

 commonly given contains a logarithm which becomes 

 infinite at a point on the vortex itself. In a further paper 

 in the same journal (xvii. [2], 9) the attraction of a thin 

 tube of finite density is discussed. 



On December 7, igoS, Mr. Herbert Chatley gave a 

 lecture on mechanical flight before the Society of 

 Engineers. The printed account of the lecture contains 

 about as clear and concise a statement of the present posi- 

 tion of the problem as could possibly be condensed into 

 fifteen pages. The relative advantages of the aeroplane, 

 hi-licopt^re and ornithopt^re are briefly stated, but the 

 point most emphasised is the need for scientific research 

 both in connection with the study of air resistance and 

 in connection with stability. These researches are bound 

 to come sooner or later, for the work is perfectly well 

 defined and straightforward, and want of opportunity has 

 been the only hindrance which has given the lead to 

 methods of trial and error. Mr. Chatley does not anticipate 

 that aerial navigation will cause any great revolution in 

 war and commerce for some years to come. He, how- 

 ever, wishes to point out the deplorable backwardness of 

 English invention in this direction. 



Prof. M. Lave, in the Physikalische Zeitschrift, ix., 

 22, pp. 778-So, directs attention to an apparent paradox 

 in the application of the concept entropy to radiation 

 phenomena. If a beam of light falling on the surface 

 separating two media is broken up into a reflected and a 

 refracted beam, the two are capable of being re-united, 

 under ideal conditions, into a single beam, and no entropy 

 change can accompany the process. On the contrarv, two 

 beams from different sources, but identically similar in all 

 other respects (non-coherent beams), cannot be so united, 

 and their total entropy is apparently greater than that of 

 the original beam. According to the statistical or proba- 

 bility definition of entropy, the difference is easily accounted 

 for. On the thermodynamic aspect, the entropy of the 

 coherent beams as a whole appears different from the 

 sum of the entropies of the parts if the latter are estimated 

 for each part independently without taking account of the 

 presence of the other. The properties do not appear to 

 be out of accord with the laws of thermodynamics so far 

 as these are defined in terms of changes of available energy 

 due to irreversible transformations. The available energy 

 NO. 2046, VOL. 79J 



of a beam of light is increased by the presence of a 

 coherent beam, and if a pair of such beams could be 

 generated from independent sources we should undoubtedly 

 be able to overcome the second law (and make our for- 

 tunes?), but such a possibility is contrary to existing ex- 

 perience. 



The method of thermal analysis, i.e. the observation of 

 the change of temperature with time of a material in a 

 cooling furnace, has been used so extensively in metal- 

 lurgical research during the last twenty years, and has 

 assumed so many different forms in the hands of experi- 

 menters, th.'it the critical examination of the various 

 methods from both experimental and theoretical points 

 of view which Mr. G. K. Burgess contributes to the 

 November (1908) number of the Bulletin of the Bureau a* 

 .Standards will be welcomed by all metallurgists. M;. 

 Burgess comes to the conclusion that from both points ol 

 view the most certain and complete data may be obtained 

 by combining the observations of variation of temperature 

 with time with those obtained by taking the differences 

 of temperatures of the material under test and a standard 

 material cooling under the same conditions. He points 

 out, however, that for accurate quantitative work it will 

 be further necessary to take into account the effect of the 

 cooling of the furnace itself on the rate of cooling of the 

 specimen within it. 



In Nature of November 19, 1908 (vol. Ixxix., p. 75), 

 Prof. Perry directed attention to the admirable pioneer 

 work in the practical teaching of science and technology 

 done by the late Prof. Ayrton so long ago as 1879 at the 

 Finsbury Technical College. Sir Oliver Lodge, in a letter 

 to Nature (vol. Ixxix., p. 129), supplemented this informa- 

 tion by an account of similar work accomplished, certainly 

 in 1872 and perhaps as far back as 1866, at King's and 

 University Colleges in London by Prof. Carey Foster and 

 others. Prof. Chas. R. Cross, of the Massachusetts Insti- 

 tute of Technology, Boston, U.S..^., now sends us a 

 printed copy of a report on the physical laboratory of the 

 institute written by Prof. E. C. Pickering, then Thayer 

 professor of physics at the institute, which shows that in 

 iSb4 President- Rogers proposed a laboratory for the 

 institute in which "the student may be exercised in a 

 variety of mechanical and physical processes and experi- 

 ments " ; and in October, 186S, "a room was opened to 

 advanced students where they carried on physical investi- 

 gations, as is done by many physicists with their special 

 students." It appears evident that even more than forty 

 years ago several men of science were beginning to 

 appreciate the need, which is now recognised universally, 

 for properly organised experimental work by students 

 themselves if the instruction given in physical science is to 

 be thorough and satisfactory. 



The Berlin Photographic Company, 133 New Bond 

 Street, \V., has sent us several portraits of distinguished 

 men of science from a collection published by the company 

 under the title "Corpus Imaginum." The portraits are 

 photogravures on plate paper, the size of the picture itself 

 being in each case about 6 inches by 9 inches, and the 

 price of each plate is 3s. We have no hesitation in say- 

 ing that the portraits are extremely fine, and that they 

 should decorate the w'alls of many studies and schools. 

 The portrait of Lord Kelvin, which is among the selection 

 sent to us, is certainly the truest picture of him we have 

 ever seen. ."Vmong other eminent men of science included 

 in the collection published by the company are Bunsen, 

 Cuvier, Darwin, Faraday, Helmholtz, Herschel, Huxley, 

 Liebig, Lister, Mendelfeff, Newton, Owen, Pasteur, Sir 



