46 



NATURE 



[May 13, 1897 



comparable with a tenth are treated as small, and their squares 

 neglected. 



If we regard the boomerang as a thin, slightly distorted 

 lamina, and integrate over it the forces indicated in S. P. 

 Langley's paper on " Experiments in Aerodynamics" (" Smith- 

 sonian Contributions to Knowledge," 1891), we can obtain 

 equations of motion. From these, treating the motion as 

 steady (to the first approximation), we may deduce the values 

 of the angular velocities on which the direction of the axis of 

 rotation depends. Five cases are worked out numerically, and 

 the various effects of the "rounding" and "twisting" agree 

 in character with the experimental facts ; the discrepancies in 

 actual magnitude are not larger than might, from the nature 

 of the case, have been anticipated. 



The theoretical results may be further tested by applying 

 them to determine the conditions favourable to the production 

 of other flights in which, after the first circle, a loop is de- 

 scribed, either in front of or behind the thrower ; in each of 

 these cases success has been attained. An explanation is also 

 afforded of the returning of a boomerang without " twist," 

 made by Mr. O. Eckenstein, and of the wonderfully long, 

 straight trajectories of some of the native non-returning 

 implements. 



Geological Society, April 28.— Dr. Henry Hicks, F.R.S., 

 President, in the chair. — The President, referring to the exhibit 

 of models of the dorsal and ventral aspect of Triarthrus, said 

 that these had been prepared and sent to him by Mr. Charles E. 

 Beecher, of Yale University Museum. He was sure that they 

 would prove of great interest to the Fellows, who were well 

 acquainted with the extremely careful work which Mr. Beecher 

 had done in connection with Triarthrtis. — The following com- 

 munications were read : — Note on a portion of the Nubian 

 Desert south-east of Korosko, by Captain H. G. Lyons, R.E., 

 with notes on the petrology by Miss C. A. Raisin, and water- 

 analyses by Miss E. Aston. A general description of the 

 physical structure of the area, which consists mainly of Nubian 

 sandstone and crystalline rocks, was given. Coming from 

 Korosko to the Murrat Wells, the crystalline rocks are first met 

 with on the east side of Jebel Raft. At Wadi dur Nabadi are 

 ancient gold-workings. The crystalline rocks are both massive 

 and schistose. On the crystalline mass of Jebel Raft, and 

 apparently overlain by the Nubian sandstone, is a very coarse 

 conglomerate containing fragments of crystalline rock, which 

 appears to be older than the Nubian sandstone. The Nubian 

 sandstone has little or no dip, and shows very slight variation 

 in composition. The water-supply of the Nubian Desert is 

 directly dependent on the rainfall, which is very irregular. The 

 wells are sunk in the detritus of the valleys, and contain a large 

 amount of mineral matter in solution, which renders them almost 

 undrinkable ; while the second source of supply — the rain-water 

 reservoirs — are deep holes in the ravines which intersect the 

 crystalline hills. These holes are attributed to water-action ; 

 and in the reservoir of Medina in Jebel Raft the spherical stones 

 which assisted in forming the pothole still occur. The author 

 believed that these ravines and reservoirs were formed at an 

 earlier period than the present, when the rainfall was heavier. 

 ]\Iiss Raisin gave accounts of both massive and schistose crystal- 

 line rocks, and also of sedimentary rocks. The crystalline 

 rocks described include gneiss, hornblendite, gabbro, often 

 much altered and resembling some of the Alpine gabbros, some 

 allied rocks containing lustre- mottled hornblende, other forms 

 of diabase, quartz-diorite, granite, felsites, certain schistose and 

 a few distinctly fragmental rocks. None of the igneous rocks 

 could be stated with certainty to have originated as a lava-flow. 

 Many of them had undergone much alteration since their con- 

 solidation, and the results of this were described. There was 

 clear evidence in many cases of erosion by desert-sand and the 

 formation of a weathered coating. The .schistose rocks did not 

 present a very modern facies, and might be late Archaean or 

 early Palteozoic. The massive crystallines may belong to 

 different epochs, but include some rocks (such as the gneiss) 

 resembling Arch^an. These seemed to mark an eastward 

 extension of the anticlinal axis previously traced by Captain 

 Lyons to Wady Haifa in the Nile Valley from the west. Miss 

 Aston gave two tables, one of which showed the actual amounts 

 of substances found in the wells of Murrat, Bir Tilat Abda, and 

 Bir Ab Anaga, while the second showed their approximate 

 constitution. — On the origin of some of the gneisses of Anglesey, 

 by Dr. Charles Callaway. The author still maintained the 

 occurrence of two pre-Cambrian groups in Anglesey, the later of 



NO. 1437, VOL. 56] 



Pebidian age. In his paper a description was given of the 

 production of gneissic structure in rocks of the earlier group 

 occurring in the south of the island. The products of meta- 

 morphism were similar to those described by the author in the 

 Malvern area, (i) Simple schists, granite is converted into 

 mica-gneiss, diorite into hornblendic or chloritic gneiss, and 

 felsite into mica-schist ; (2) Injection-schists. 



Zoological Society, May 4. — Mr. Herbert Druce, in the 

 chair. — Mr. Oldfield Thomas exhibited a selection of the Mam- 

 mals recently collected by Mr. A. Whyte during his expedition to 

 the Nyika plateau and the Masuku mountains. North Nyasa. Mr. 

 Thomas de.scribed as new a squirrel [Xertis lucifer), brilliant 

 rufous throughout, with a black dorsal patch ; a reed-rat 

 {Thryonoinys sclaleri), allied to T. gi-egortanus, but with a 

 longer tail, whitish instead of yellowish underside, and narrower 

 and differently shaped skull ; a mole-rat (Georychus whytei), like 

 G. niinrodt\ but with longer and broader frontal premaxillary 

 processes ; a pouched mouse {Saciostomus elegans), of a general 

 buff colour and with a longer head than S. campestris : and Mas 

 nyikte, a rat of the size of Miis chrysophihis, but darker in 

 colour and with a more rounded skull. A new subgeneric term 

 {Gerbillisctts) was suggested for Gerhillus boehmi, Noack, of 

 which Mr. Whyte had sent home specimens. Mr. Thomas 

 also stated that the peculiar bulbous-tipped tail hairs described 

 in Pelrodrovtus proved to be confined to and characteristic of 

 East African examples of the genus, which might therefore be 

 specifically separated from the Zambezi forms as P. sullani. — Mr. 

 Howard Saunders exhibited, on behalf of Mr. Henry Evans, 

 a series of instantaneous photographs of the great grey seal 

 {Halichtzrus gryphus) which had been taken in the Outer 

 Hebrides. — Mr. J. E. S. Moore gave a general account, 

 illustrated with the optical lantern, of the zoological results of 

 his expedition to Lake Tanganyika in 1895 and 1896. Mr. 

 Moore stated that the main object of the expedition had been to 

 obtain materials for the morphological study of certain hitherto 

 uninvestigated animal forms. It appeared that a key to the 

 general interpretation of the lake-faunas of Central Africa would 

 be most readily obtained by a study of their Molluscan Types. 

 These showed that the faunas of most of the vast inland reser- 

 voirs of Africa were composed of normal lacustrine stocks, but 

 that in Lake Tanganyika there were strange forms which cer- 

 tainly could not be included among such groups. All these 

 forms appeared to have marine affinities ; but, as they could 

 not be directly associated with any living oceanic species, it was 

 argued that they were probably the survivors of the marine fauna 

 of some more ancient times, when Tanganyika was connected 

 with the ocean. This theory was supported by the similarity 

 of certain Tanganyika gastropods to ancient fossil shells. — A 

 communication was read from Mr. Walter E. Collingc, on some 

 European slugs of the genus Arion. — Mr. Sclater read a com- 

 munication from Mr. Frederick J. Jackson, containing field- 

 notes on the antelopes of Mau District, British East Africa. — 

 The Rev. H. S. Gorham contributed a paper on the Coleoptera 

 of the family Endomychid(c of the Eastern Hemisphere. 

 Eighteen species were described, of which eleven were charac- 

 terised as new. — Mr. F. E. Beddard, F. R.S., read a note upon 

 the presence of intercentra in the vertebral column of birds. 

 The existence of free intercentra in the caudal region was 

 described in a number of genera belonging to many families of 

 birds. 



Manchester. 



Literary and Philosophical Society, April 27.— Dr. E. 

 Schunck, F.R.S., President, in the chair. — Sir Henry E. Roscue, 

 F. R.S., was elected an honorary member. The following were 

 elected officers and members of the Council for the ensuing 

 year : — President, J. Cosmo Melvill ; Vice-Presidents, Prof, O. 

 Reynolds, F.R.S., Prof. A. Schuster, F.R.S., Charles Bailey, 

 and W. H Johnson ; Secretaries, R. F. Gwyther and Francis 

 Jones ; Treasurer, J. J. Ashworth ; Librarian, W. E. Hoyle ; 

 other members of che Council, Prof. H. B. Dixon, F.R.S., 

 Ptof. H. Lamb, F.R S. , Dr. A. Hodgkinson, Francis Nichol- 

 son, J. E. King, and R. L. Taylor. — On the composition of 

 some ancient Egyptian bronze and iron implements, by Dr. A. 

 Harden. The author communicated the results of the analysis of 

 two ancient iron chisels found in Thebes, and dating from about 

 600 B.C. Both of the implements contain a very small amount 

 of carbon, and could not be rendered very hard by tempering. 

 A specimen of bronze, dating from about 1500 B.C., was found 

 to resemble modern bronze in its composition, consisting of 

 copper alloyed with tin. 



