The new system of traction for limber-coupled wagons is one which causes the limber and the carriage to constitute two mechanical levers which, at such times as the resistance to traction is small, carry a part of the weight of the animal, while when it is great, they cause an automatic transference of weight from the wheels to the animal; thus securing an ever-varying virtual angle of traction. The same effect is automatically brought about to the advantage of the horse by each of the inventor's new appliances. The same conditions are obtained in the case of man-hauled vehicles. 2. Report on Complex Stress Distribution.--See Reports, p. 159. 3. The Strength of Iron, Steel, and Cast-iron Struts. A series of experiments on solid free-ended centrally-loaded struts has been carried out in the Engineering Laboratories of the Manchester University during the last two years. They lead to the following conclusions : 1. For all the struts tested the collapsing load was in accordance with the values calculated from Euler's formula, except for struts so short that the average stress produced by the theoretical load was above the elastic limit of the material. 2. In the case of the shorter struts the material tested may be divided into two classes : (a) Materials having no appreciable drop of stress at yield (cast iron and bright-rolled steel). For such materials, Southwell's formula-of which Euler's is the particular case for wholly elastic material-gives the collapsing load for all lengths. (b) Materials having a decided drop of stress at yield (mild steel, wrought iron, and high tensile steel). For such materials Euler's or Southwell's formula applies for all lengths for which the average stress calculated is less than the elastic limit. Southwell's formula applies between the elastic limit and the yield point, and for the shortest struts the collapsing load is equal to the yield stress multiplied by the area. 4. The Calculation of Torsion Stresses in Framed Structures and Thinwalled Prisms. By Professor CYRIL BATHO, M.Sc., B. Eng. In designing a double track cantilever bridge with suspended span, it is necessary to calculate the stresses arising in the suspended span due to unsymmetrical live loads on the cantilever and anchor arms. It is also sometimes of importance to determine the stresses in an ordinary truss-bridge, braced arch or other framed structure on four supports due to unequal settlement of the supports. Similar problems arise in connection with erection travellers carrying unsymmetrical loads, &c. The stresses arising under such conditions may be termed torsion stresses. The calculation of these may be considerably shortened by the use of the following theorems : If a framed structure consisting of two parallel trusses, similar in outline and connected by lateral bracing, be subjected to unit forces at the corners forming a pair of equal and opposite couples in the planes of the two trusses respectively, the shear perpendicular to the plane of the trusses is constant throughout the lateral system and equal to the area of the base of the frame work divided by twice the area of one of the trusses. The theorem may be extended to include thin-walled prisms, and in its most general form may be stated thus: If a hollow cylinder or prism, either continuous walled or of framework and having plane ends perpendicular to its length, be subjected to a twisting moment by couples in the planes of its ends, the total longitudinal shear is everywhere constant and equal to the twisting moment multiplied by See Engineering, October 15, 1915, p. 392. the length of the cylinder and divided by twice the area of one of its ends. Three examples are considered in the paper: (i) A bridge having parallel chords and panels of equal length. (ii) A thin-walled rectangular box. The results in these cases are shown to be in agreement with those given by other and longer methods. (iii) The torsion stresses in the suspended span of a bridge similar in design to the New Quebec bridge. In this example it is shown how the stresses in the lateral system may be calculated immediately by use of the above theorem, and how the stresses in the main trusses may be found by means of a short graphical process. 5. An Inquiry into the Possible Existence of Mutual Induction between Masses. By Professor MILES WALKER. The closeness of the analogy in the behaviour of matter in motion and electricity flowing in a circuit leads us to inquire, Is there any action between masses analogous to the mutual induction between electric circuits?' If we accelerate a fly-wheel does it produce any force upon an adjacent co-axial disc? It is quite possible that a small force of the kind might pass unnoticed if not specially looked for, just as the gravitational attraction between two movable bodies would ordinarily escape observation. The author described and exhibited apparatus constructed at the Manchester School of Technology in 1912 for the purpose of finding out whether any force of the kind is observable. A steel fly-wheel, A, 56 cms. in diameter and 11 cms. thick, is mounted on a vertical shaft and driven by an electric motor. Above the fly-wheel is suspended a disc, B, 51 cms. in diameter, made of very pure porcelain, weighing about 10 kilograms. The suspension is made of two round steel wires each 025 cm. in diameter. The length of the suspension is 21 mètres. The distance between the bifilars is about 0:15 cm. The torsional control on B is extremely small, amounting to only 28 dyne-cms. for a deflection of 1 radiam. The angular swing of B upon its principal axis has a natural period of 2,460 seconds. A mirror is attached to B, which enables the movement to be accurately observed on a scale at 6 mètres distance. A movement of 01 cm. on the scale corresponding to a deflection of 1/12,000 of a radiam can be estimated, so that one can observe the effect of acting on the edge of the disc with a force amounting to only 10-11 of the weight of the disc. The paper described some of the precautions taken to avoid the effect of accidental disturbances. The procedure in making the experiment is as follows: The disc B is brought as nearly as possible to rest. The fly-wheel A is then rapidly accelerated (say, anti-clock-wise) and run up to a speed of 2,700 r.p.m., so as to give an impulse to B if that were possible. The speed is then maintained constant for one-half the natural period of the swing of B. The fly-wheel is then rapidly slowed down and the direction of rotation reversed and the speed increased to 2,700 r.p.m. (clock-wise). This is repeated several times, so as to set up resonance in B. Bmon In the early experiments made in 1913 it was found that if there were any effects of the kind looked for they were of an exceedingly small order, and that the observed movements of B were mainly due to accidental disturbing forces. At this time it was possible to assert that the ratio the change in the angular momentum of B to that of A, was certainly less than 23 x 10-8. In the later experiments the chief aim was to diminish the disturbing forces as far as possible, so that the negative result might be stated with the smallest possible limit of error. The introduction of a suspended screen and other refinements so improved the steadiness of B while A was running that we can now state that the ratio for this apparatus is less than 5 x 10-10. SECTION H.-ANTHROPOLOGY. PRESIDENT OF THE SECTION.--PROFESSOR C. G. SELIGMAN, M.D. WEDNESDAY, SEPTEMBER 8. The President delivered the following Address : : It is impossible to pass to the subject of my address without first referring to the heavy losses which the Teutonic lust of power has inflicted upon our science, no less than upon every other department of humane and beneficent activity. Whatever loss we may yet be called upon to endure there can hardly be any more regrettable than the death of Joseph Déchelette, whose acknowledged eminence makes any detailed account of his labours superfluous. I will but mention his Manuel d'Archéologie, a work of rare lucidity, which though unfinished (the pity of it) will long be authoritative upon European prehistory and archæology. His valour was no less than his erudition, for though his age exempted him from all military duties, he insisted on taking his place at the head of his old company of Territorials, and was killed last October while leading his men in a charge that carried the line forward 300 yards. How he died may be learnt from the official army order quoted in L'Anthropologie (vol. 25, p. 581). We have also to mourn the death of Robert Hertz, a regular contributor to L'Année Sociologique, and of Jean Maspero, son of Sir Gaston Maspero, an authority on the Byzantine period and Arabic geography. The other men whose premature death we deplore belong for the most part to that brilliant band of French soldier-explorers to which African ethnography owes so much. Captain René Avelot, whose name will be known to every reader of L'Anthropologie, was also the author of important papers in La Géographie and other geographical periodicals. He had hoped to devote himself entirely to ethnological work, and at the outbreak of war was about to publish a series of studies on the natives of the French Congo, Darfur, and Wadai. Before going to the front he arranged for the publication of these, even in the event of his death. Captain Morice Cortier, a geographer and an explorer rather than an ethnologist, was engaged at the time of his death in preparing a work on the prehistory of the Sahara. Captain Maurice Bourlon received his scientific training in the Dordogne. He conducted excavations in the neighbourhood of Les Eyzies, where he made a number of discoveries, and brought to light some remarkable specimens of palæolithic art. We dare not hope that the foregoing list is final, and while mourning their loss we cannot pay greater honour to their memory than by taking up the burden they relinquished in the hour of their country's supreme need. In my address I shall endeavour to outline the early history of the AngloEgyptian Sudan from the standpoint of the ethnologist, and thus indicate some of the lines upon which future research may most usefully proceed. Fortunately the Sudan is one of those areas in which the site and scope of work may be selected from the point of view of immediate scientific interest, without any grave dereliction of duty. There is not the danger so frequently met with, in the Pacific for example, of finding that civilisation has come stealthily and swept away the greater part of the old order. The Sudan has not been civilised to such a point that the ethnologist need feel it his bounden duty to visit the most sophisticated areas in order to record everything that is in danger of being lost. If I seem overbold in trying to present a summary account of so vast an area, I can plead certain extenuating circumstances. Firstly, I had the good fortune to be asked by the Sudan Government to conduct a small ethnographic survey for them, in the course of which I have spent two winters in the field; secondly, although it is nearly twenty years since the reconquest of the Sudan, the amount of ethnographical material which has accumulated is far less than might have been expected. Nowhere has there been any intensive study of even a single people, though conditions are as favourable as could be desired in at least three quarters of the country. It would be an interesting, if melancholy, task to try to determine why so little has been done. Certainly the failure is not due to lack of interest on the part of the Sirdar and his Council, for, apart from the funds provided for my expeditions, the Government has paid the expenses of publishing the only considerable work of serious scientific interest dealing with Sudanese tribes that has yet been written by any of its officers. It is worth noting that archæologists have been more energetic than ethnologists, partly no doubt owing to the stimulus provided by the discoveries of the Nubian Archæological Survey, but, even apart from this, more interest seems to be taken in the ancient history of the country than in its living races. Surprisingly little is yet known of the prehistory of the Anglo-Egyptian Sudan. No implement of river drift type appears to have been found, and while admitting that this may be due to incomplete exploration, the fact seems of some significance considering the abundance of specimens of this type which have been found on the surface in Egypt, Southern Tunisia and South Africa. With regard to implements of Le Moustier type, I may allude to certain specimens which I have myself collected from two sites, namely from Beraeis in north-west Kordofan, situated on a sandy plateau at the foot of Jebel Katul between two small spurs of the main rock mass, and from Jebel Gule in Dar Fung. At the former site I found a number of roughly worked unpolished stones near the foot of the hill between the village and the burial ground, and also within the latter. The majority are moderately thin broad flakes, showing a well-marked bulb of percussion, and little or no secondary working; other specimens are shorter and stouter. One surface is flat and unworked, the opposite curved surface shows a number of facets separated by rather prominent crests, all except the central facets sloping more or less steeply to the working edge. In some specimens the crests are sufficiently prominent to give a somewhat fluted aspect to the slope and a crenelated edge, one portion of which often shows signs of having been worn down and retouched. These implements, which I had suspected might have been Aurignacian, were considered by M. Breuil to belong to the Moustierian period, and he referred to the same period and industry some thick, fluted and engrailed scrapers from Jebel Gule, which I have described as resembling the paleolithic discs from Suffolk and other localities (19. 211), as well as some implements of other forms which presented a paleolithic facies. While the Beraeis stones are so rough that they may perhaps be rejects, this does not apply to the specimens from Jebel Gule. Besides the disc and Moustierian points there is one implement which M. Breuil regards as a true, but much worn, coup-depoing of Moustierian age. Whether all these really date from the Moustierian period or not, certain of the specimens from Jebel Gule show a surprising resemblance to South African specimens figured and described by Dr. L. Peringuey as of Aurignacian type (14 Pls. xvi. 13o, xi. 60, xviii. 13), or in other words of the Capsien type of Tunisia. Evidence concerning the later Stone Age is furnished by a number of finds made on widely scattered sites; but though no explanation can be offered it should be noted that no stone implement of any kind has been recorded from the Red Sea Province, although it is one of the best known parts of the Sudan, and has been the scene of considerable engineering efforts. This is the more remarkable in view of the geographical features of the country; the absence of forest, the weathered plateaux, the valleys filled with deposits through which innumerable wadis have been cut, all suggest that if stone implements existed me at least should have come to light. Much interest attaches to the distribu } tion of ground stone axes in the Nile valley. While there is probably no museum with any pretence to an Egyptian collection which has not a number of these, and though they can be bought in almost every curio shop in Cairo, I have been unable to find any record of their discovery in a tomb group or undisturbed burial in Egypt; so that considering the number of prehistoric burials that have been examined, it can be said that they were scarcely if at all known in predynastic Egypt. On the other hand, they are common in Nubia, where a number have been found in predynastic and early dynastic tombs (2 Pl. 63). Many examples have come from Meroe, and I believe that specimens occur on every site of neolithic date in the Sudan. They have certainly been found at Jebel Sabaat, at Jebel Geili 90 miles east of Khartum, at Jebel Gule and at Faragab. Moreover, the rock faces on which they were ground have been found both at Jebel Gule and Jebel Geili. We may therefore attribute a southern source to the ground stone axes of the Nile valley, and in the light of our present knowledge regard them as of Negro origin. This view is supported by the results of recent work on the prehistory of the Sahara. Gautier, who has devoted much time to the ethnography of the French Sudan, points out that while at the end of the neolithic period the northern Sahara had a stone industry characterised by unpolished implements of Egyptian affinities, in the central and southern Sahara the typical implement was the polished axe, and that this was of Sudanese Negro origin (7, 326). That the boundary of the two provinces seems to have coincided roughly with the present southern boundary of Algeria, i.e., that the Berber-Negro frontier was then some 1,000 kilomètres further north than it is at present, is in no way opposed to this view. Perforated discs or rings and hollow conical and spherical stones, all ground in the usual neolithic style, have been found, notably at Meroë, on Jebel Haraza (W. Kordofan) and at Jebel Geili, where I believe stone discs and axe heads can be definitely associated together. Besides the types already alluded to Jebel Gule yielded a large number of pygmy implements of quartz, carnelian, and hornstone. These are similar to those found in South Africa and attributed to Bushmen, and there is reason to believe that this industry also existed at Faragab, where the innumerable disc beads of ostrich egg shell were probably bored with more or less worked up slivers of quartz. The distribution of stone arrow heads in the Nile valley is also of much interest, but the data are as yet insufficient for discussion. It may, however, be worth while to point out that the transverse arrow head with its chisel-like edge cannot be of Negro origin, although the wooden figures of Negro bowmen from the tomb of Emseht, a general of the XI. dynasty, are armed with arrows with heads of this form, and the same type of arrow head is in use to this day among the tribes of the Kwilu and Kasai districts of the Belgian Congo. Some mention must be made of the existence of stone monuments of megalithic type in the Sudan, although their number is small and their origin obscure. There is a monolith about two mètres high on the plateau overlooking the Khor el Arab, near the Sinkat-Erkowit road, to which tradition says Mohammed tied his horse. Another monolith of much the same dimensions has been described and figured by Crowfoot from Isa Derheib inland from Akik (4 Pl.). At present there seems no reason to attribute any great antiquity to these stones; presumably they are connected with the upright stones and 'stelai' of Axum. Probably other rude stone monuments will be found in the Red Sea Province; indeed, I have heard of such, though the information was never very precise. It is, however, worth noting that typical dolmens do occur in the Madi country in the southern Sudan (26, 123).1 When the time comes to estimate the significance of the Sudanese monuments of megalithic types, it will be necessary to remember that, although uncommon, they do occur in Egypt. Indeed, Déchelette has suggested that their rarity in Egypt is only due to their having been nearly all destroyed. Meanwhile it may be noted that de Morgan has published the drawing of a stone circle at Jebel Genamieh in the desert to the east of Edfu; that N. de G. Davies found perfect miniature dolmens or cists at Tel el Amarna; that somewhat similar structures containing human remains have been described by Schweinfurth near El Kab; and that I have found them on the high desert plateau a few miles north of Abydos. |