Jime 15, 1882] 



NA TURE 



167 



bow one prong only, therefore, in this case, the vibration must 

 proceed along the prongs. A light fork 1 metre long was fixed 

 in a heavy vice, and it was shown by it that vibrations passed 

 down one prong and up the other alternately. By means of 

 dust, ripples were shown to ran down an ordinary fork in vibra- 

 tion. Light pieces of metal were fitted to the ends of a power- 

 ful fork, and these immersed in mercury, the reflected surface 

 of which was shown on a screen, where it was seen that the 

 whole mercury surface was broken into fine ripples. It was 

 suggested that such small waves are also perceived by the ear. 

 By these, certain conditions of harmonics could be better ac- 

 counted for, as, for example, by division in smaller waves, the 

 rarefaction of a note in space would not suffer interference by 

 the condensation of its octave falling in the same space and time. 

 — Lord Rayleigh explained several of Mr. Stanley's experiments 

 on the known theory of sound. — Mr. Walter Bailey then ex- 

 hibited a model of a new " integratiug anemometer." This 

 apparatus contains a horizontal plane, in which are two slits 

 forming a cross with arms towards the cardinal points. Each 

 slit is fitted with a sliding-piece, and the two slides are connected 

 by a bar; the arrangement being that of the well-known, instru- 

 ment for drawing ellipses. The slides carry beneath them 

 wheels with their planes perpendicular to the slits, and passing 

 through the pivots of the bar. The wheels rest on a horizontal 

 disk, whose centre is beneath the centre of the cross. The 

 centre of the bar is to be connected to a w eathercock which will 

 keep it in the direction of the wind when looked at from the 

 centre of the instrument. The disk is to be revolved by Robin- 

 son's cups. The number of revolutions of the wheels then give 

 the integral of the resolved parts of the w ind in the direction of 

 the cardinal points. In the working model of the instrument 

 exhibited there was an electrical arrangement connected with 

 four indicators, one for each of the cardinal points. At each 

 turn of a wheel a circuit was completed, and the corresponding 

 iudicator moved. Recording instruments are to be substituted 

 for indicators, and the amount recorded on each in a given time 

 will be proportional to the total motion of the wind towards the 

 corresponding cardinal point. — Mr. Lecky pointed out that a 

 good anemometer was a great desideratum at present. — The 

 Society meets at Oxford on the 17th, and South Kensington on 

 the 24th of this month. 



Anthropological Institute, May 23.— General Pitt-Rivers, 

 F.R.S., president, in the chair. — A paper was read by the Right 

 Hon. Sir H. Bartle Frere, Bart., on systems of land tenure 

 among aboriginal tribes of South Africa." The author indicated 

 the points regarding which further inquiry is needed, and urged 

 the importance of recording observations whilst it is still possible 

 to obtain information from sources which in the course of another 

 generation may be closed for ever by the extinction of races. 

 The Zulu title to the lands in South Africa rests simply on force, 

 the land being his property only so long as the occupant can hold it 

 by himself, or with the assistance of the chief who protects him. 

 The tenure cannot be transmitted by inheritance wiihout being 

 constantly sapped by the influence of two institutions universal 

 among the Zulus, viz., polygamy and slavery. Christianity has 

 a special bearing on the subject of land tenure, because it is 

 mainly through its agency, indirect as well as direct, that we 

 may look for such changes in the customs of the races of South 

 Africa as may civilise and settle them, and put an end to the 

 ceaseless wanderings which have tended so powerfully to keep 

 them in a state of ever-recurring barbarism. The author's im- 

 pression was that the advancement and civilisation of the native 

 tribes of South Africa depend greatly upon the extent to which 

 individual tenure of property can be extended, whilst some 

 patriarchal authority such as "seems inherent in the head of a 

 family or kraal is recognised, and invested with some sort of 

 magisterial and judicial functions, sufficient to meet the every- 

 day exigencies of village life. The President opened the discus- 

 sion with some remarks on the peculiarities of land tenure in 

 various parts of the world, and was followed by Dr. Rae, Mr. 

 Hyde Clarke, and Miss Buckland.— On the motion of Prof. 

 Flower, a cordial vote of thanks was given to the president and 

 Mrs. Pitt-Rivers for their kind less in allowing the meeting to 

 be held at their house. 



Edinburgh 

 Royal Society, June 5.— The Right Hon. Lord Moncrieff, 

 president, in the chair. —Obituary notices of Dr. Lauder Lindsay, 



Mr. David Smith, and Prof. Peirce of Harvard, were read. 



The Council announced the award of the Keith Prize for the 



Biennial Period 1879-81, to Prof. Chrystal, for his paper on the 

 differential telephone, which is published in the Society's Tran- 

 sactions (1879-80), and gives a new, simple, and accurate 

 method of measuring capacities and co-efficients of mutual and 

 self-induction (see Nature, vol. xxii. p. 331) ; and of the Neill 

 prize, for the triennial period 1877-80, to Mr. John Murray, for 

 his paper on the structure and origin of coral reefs and islands, 

 communicated to the Society on April 5, 1880, and printed (in 

 abstract) in the Proceedings of that date (see Nature, vol. xxii. 

 P\ 35 1 )-— Prof. Tait communicated Part II. of his paper on 

 mirage. Having formerly shown that the observed phenomena 

 could be explained in a general way by assuming a certain rela- 

 tion to exist between the refractive index of the air at any point, 

 and its situation between two planes of approximately stationary 

 density ; the author, in his second paper, proceeded to investigate 

 the conditions more carefully, so as to find, if possible, a distri- 

 bution of atmospheric density which should be at once probable, 

 and produce mirage phenomena the same in all important parti- 

 culars as those observed by Scoresby, Vince, and others, and at 

 the same time be capable of easy mathematical treatment. Two 

 horizontal strata of uniform but different densities, separated by 

 a stratum whose density varies continuously from the one to the 

 other, were fouud to give results in close agreement with obser- 

 vation. That a stratum of air should remain of practically 

 uniform density through even a comparatively small height 

 requires a lowering of temperature to compensate for the dimi- 

 nution of pressure as the height increases ; but this rate of 

 change of temperature Prof. Tait showed was not gieaterjthan 

 had been observed in balloon ascents. With given thicknesses of 

 strata, there was a critical minimum distance at which mirage 

 could be obtained. For greater distances there were three 

 images, two direct and one inverted. The inverted one was 

 always larger than the lower direct one, but only appreciably so 

 when the distance of the object approached this critical minimum 

 value, for which the phenomenon known as " looming" became 

 evident. The second direct image is usually much the smallest, 

 being, except at distances near this same critical distance, so 

 small as to be practically invisible. This seems fully to account 

 for the comparatively few instances in which the three images 

 have been observed. Multiple inverted images, as observed by 

 Scoresby, were explained as due to thin successive layers of 

 varying density at different heights. It was shown that Wollas- 

 ton's illustrative experiment, in which three images are produced, 

 is not quite analogous to the state of affairs which produce them 

 naturally. In order to make it so, the tank must be greatly 

 increased in length, and the difference of density of the inter- 

 diffusing fluids greatly diminished ; so that the rays -may enter 

 and leave the transition stratum by its lower side, and not by its 

 ends. The rest of the paper showed how Wollaston's arrange- 

 ment could be simply and accurately applied to measurement of 

 rates of diffusion. — Mr. Milne Home communicated the Eighth 

 Report of the Boulder Committee, This dealt mainly with the 

 boulders around Ben Nevis, which had been examined by Prof. 

 Heddle, Prof. Duns, and Mr. Livingston of Fort William. 



Physical Society, May 26.— Prof, du Bois-Reymond in the 

 chair. — Prof. Iandolt showed a new polarisation-apparatus, 

 whose polarising part is formed according to the method of M. 

 Cornu, modified by Herr Lippich, and which has this advantage 

 over others, especially, that it is not mounted on a foot, but on a 

 solid base, whereby bending and torsion of the tube which holds 

 the liquid are avoided. This tube is inclosed in a cylindrical 

 envelope, in which water of any desired temperature can circu- 

 late. By a simple lever movement, the tube filled with the 

 experimental liquid can at any time be directly replaced by an 

 empty tube, and conversely ; so that the zero p int can be con- 

 trolled as often as desired. In its present form, the apparatus 

 is ■ pretty perfect for scientific researches; further improvement 

 must be directed principally to the production «f a good light- 

 source. Some proposed alterations of the apparatus, now in 

 hand, will afford the opportunity of examining vapours in refer- 

 ence to their rotatory power. — Dr. Hagen reported on experi- 

 ments for measuring the vapour-tension of mercury at different 

 temperatures. He first indicated briefly the apparatus Regnault 

 used, and the results obtained with it, by that physicist. The 

 values given by Regnault are met with in all text-hooks of 

 physics; yet they differ very considerably from the amounts 

 found by Regnault in his experiments, and the e do not agree 

 together. The author, therefore, undertook a new determina- 



