May 5, 1881] 



NATURE 



23 



cumbering the ground, and that the remaining lo per cent., if 

 useful, are very imperfect. One instance of the evil done by 

 such means will suffice. Sir Wm. Fairbairi, to whom is due 

 the credit of being the earliest labourer in this field, experi- 

 mented on certain single- and double-riveted joints, and found 

 that the "proportion of strength" in the case of the former 

 was 56 per cent., and in the latter 70 per cent, of the solid plate. 

 These figures, which of course applied only to the particular 

 designs tested, have been repeated in almost all manuals of 

 engineering as if they were universally true ; disregarding the 

 obvious fact that a double-riveted joint could be made just as 

 weak as a single- riveted one, by simply spacing the holes in the 

 outside row at tlie same distance. 



The Committee wisely determined to throw aside the volu- 

 minous labours of their predecessors, and begin de novo a con- 

 nected series of experiments, based on the tnie and scientific 

 method described above. We cannot find space to consider the 

 many collateral points with which these experiments will have to 

 deal, much less to give any account of the results which they 

 are to supersede. These, as embodied in this Report, will 

 remain a singular instance of the lamentable waste of money so 

 continually incurred in engineering experiments. There can be 

 little doubt that less than a tenth of this money, if applied on 

 the scientific and proper method, would have set the whole 

 question long ago at rest, and would now be saving the world, 

 through increased economy of construction, many hundreds per 

 annum for every pound so expended. 



Friction. — The last of the three subjects under consideration is 

 that of Friction at High Velocities, the Report on which has 

 been prepared by Prof. Kennedy, of University College, London. 

 This subject offers a curious instance of the influence exercised 

 by a distinguished experimenter, and how his conclusions are 

 pushed, by those who blindly follow his guidance, much further 

 than he himself would attempt to go. About fifty years ago 

 the late General Morin made an important series of experiments, 

 from which the well-known " Laws of Friction" were deduced. 

 One of these laws is that the friction between solid bodies in 

 motion, or dynamical friction, is independent of the velocity. 

 It was overlooked, by tliose who announced this law, that the 

 experiments were only conducted with certain silbstances under 

 small pressures and at mnderate speeds. General Morin himself, 

 in an interesting letter published in the present Report, expressly 

 states that he had himself always regarded his results, " not as 

 mathematical laws, but as close ajiproximations to the truth 

 within the Vnnits of the data of the experiments themselves." Un- 

 fortunately oUaers did not imitate this caution : they asserted 

 everywhere that the law was universal, and by many it is asserted 

 to be so still. 



That it is not universal has however been sufficiently proved. 

 At the time of the launch of the Great Eastern the late Mr. 

 Froude showed, by experiments on a large scale, that the fric- 

 tion of a ve^sel on the launching-ways decreased rapidly as the 

 velocity increased. In 1S51 Poiree and Bochet showed that the 

 coefficient of friction of railway wheels sliding on rails dimin- 

 ished very rapidly with increase of speed (between limits of 900 

 and 3600 feet per minute). Recently Capt. Douglas Galton and 

 Mr. Westinghouse made a long series of experiments on the 

 friction of railway-brakes (cast-iron blocks on steel lyres), and 

 their results showed a marked decrease of friction, with in- 

 crease of speed, within the very large range of 400 to 5300 

 feet per minute. Prof. Kimball has made experiments at much 

 lower speeds (about i to 100 feet per minute), both with pieces 

 of wood and with wrought-iron spindles in cast-iron bearmgs ; 

 and he also finds a rapid decrease of friction with increase of 

 speed. At the lowest possible speeds (o'oia^to o"6 feet per minute) 

 Prof. Fleeming Jenkin finds a similar decrease, pointing to the 

 supposition that the change from statical to dynamical friction 

 is not sudden, but continuous. Lastly, Prof R. H. Thurston 

 has made an elaborate set of experiments on the frictional resist- 

 ance of lubricated bearings. He arrives at the conclusion that 

 for cool and well-lubricated bearings the coefficient of friction 

 decreases up to a speed of about 100 feet per minute, and after- 

 wards increases with the speed approximately as its fifth root. 

 The details of th&e experiments do not seem to have been 

 published, so that it is not certain how far this curious result 

 may be taken to hold. 



It will be seen that none of these various experiments confirm 

 the universal law deduced from Morin's results, viz. that dynami- 

 cal friction is independent of velocity. On the contrary, it may 

 be taken as proved for unlubrieated surfaces (such as rad^^ay 

 brakes) that the coefficient of friction diminishes rapidly with 



increase of velocity ; although the exact law of variation and its 

 relation to the pressure on the surfaces is not fully determined. 

 With lubricated surfaces the same fact may be assumed to be 

 true at speeds up to 100 feet per minute ; but above this, if we 

 accept Prof. Thurston's results, the result is the op, osite. It 

 seems clear that the question is ripe for further mves'igation, 

 which might take the form, first of repeating and extending 

 Thurston's experiments with lubricants, and secondly of ascer- 

 taining the law of variation w'ith unlubrieated surfaces more 

 exactly than could be done by the aid of the experiments hitherto 

 carried out. 



UNIVERSITY AND EDUCATIONAL 

 INTELLIGENCE 



Cambridge. — At the Downing College Examination in June, 

 1881, one Foundation Scholarship of the annual value of 80/. 

 will be thrown open to all members of the University who have 

 not kept more than six terms. The subjects of this I'.xamination 

 will be Chemistry (Theoretical and Practical), Physics (Heat, 

 Electricity, and Masnetism), Comparative Anatomy, Physiology, 

 and Botany, The Examinations for Minor Scholarships, which 

 are open to all persons who have not entered at any college in 

 the L'niver-ity or who h.ave not resided one entire term in any 

 such college, will be held in Downing College on Tuesday, May 

 31, and three following days. F'urther information will ha given 

 by Mr. J. Perkins or by the Rev. J. C. Saunders, tutors of the 

 College. 



At a special meeting of the Fellows of Gonville and Caius 

 College, held on the 30th ult., Dr. Paget, F.R.S., Regius Pro- 

 fessor of Physic in the University, and Mr. Pattison Muir, Hon. 

 M.A. (Cantab.), were elected Fellows of the Society. Dr. 

 Paget was formerly a Fellow of Caius College. 



Oxford. — In addition to the courses of lectures in Natural 

 Science enumerated last week, the following courses will be held 

 during this term in the University Museum :— Prof. Price will 

 lecture on physical optics, and Prof. Westwood will lecture on 

 the orders of the Arthropoda. In the absence of Prof. Rolles- 

 ton, who is abroad on account of ill-health, Mr. Jackson will 

 form classes for general catechetical instruction, while classes 

 w ill be formed by Mr. Robertson for practical microscopy, and 

 by Mr. Thomas for the study of the developing chick. 



At the Botanical Girdens Prof. Lawson will lecture on ele- 

 mentary botany (devel m ment), and will continue his course on 

 the dissection of plants. 



In the Geoloyical Department under Prof. Prestwich, lectures 

 will be given on s me of the secondary and quaternary strata. 

 The Professor will have excursions to inspect the sections of 

 the several formations around Oxford, commencingon Siturday, 

 April 30, and to be continued through May. On each \> ecediiig 

 Friday he will lecture on the subject of the following .'Saturday's 

 excursion, or on some other subject of which notice will be 

 previou-ly given. Notice will also be given in the Gazette of 

 the preceding week, and in the Museum, of the places to be 

 visited, hours of nieetinij, &c. 



In a congregation ho den on Tuesday, May 3, th • proposal to 

 allow selected candidates for the Indian Civil Service to obtain 

 the B. A. degr t- afte wo years' residence, was thrown out. An 

 amendment^to excuse selected candidates from responsions only 

 was carried by 63 v tes to 49. 



The scheme for the establishment of a University College in 

 Liverpool is now almost matured, and it is expected that the 

 College will open for its first session in October next. The 

 donations have reached the sum of 100,000/., and the task 

 of drafting a constitution for the College is now being performed 

 by a special c .mmittee. The Earl of Derby h.as accepted the 

 office of pre-ident, the vice-presidents being Mr. Christopher 

 -Bushell and Mr. William Rathbone, M.P. 



SCIENTIFIC SERIALS 



Journal de Physique, April.— Theory of machines with alter- 

 nating current^, bx -M. loubert.— On radiophony (sec nd memoir), 

 by M. Mercadierl-A'.plication of Talbot's fringe, to determin- 

 ation of the refract ve indices of liquids, byM. Hunm. -Appara- 

 tus for projectin-- i a ue at any distance with a variable enlarge- 

 ment by M Cr v ,. — -trong and constant voltaic pile, furnishing 

 residues capable- f regeneration by electrolysis, by M. Reynier. 



