December i6, 1897] 



NATURE 



167 



author of the present paper maintained that certain conglomerates 

 and associated rocks occurring for some distance north east and 

 south-west of Llanberis, which had hitherto been considered to 

 He below the workable slates of the Cambrian rocks of that area, 

 were in reality unconformable deposits of later date than those 

 slates. In the year 1894 a paper appeared in the same journal, 

 in which the authors maintained that in no case which had been 

 examined could any valid evidence be found in favour of the 

 alleged unconformity, and that in one (on the north-east side of 

 Llyn Padarn) which they supposed to afford the most satis- 

 factory proof of it, the facts were wholly opposed to the notion. 

 The present paper was a reply to these authors, in which their 

 objections, founded on general considerations, on field observa- 

 tions, and on microscopic examination of rock-specimens, were 

 discussed, and the author gave the results of further observations 

 on the rocks':of the district. — The geology of Lambiy Island, Co. 

 Dublin, by Messrs. C. I. Gardiner and S. II. Reynolds. The 

 authors, who have previously described the neighbouring district 

 of Portraine((?«rtr/. /ourn. Gto\. Soc, December 1897), under- 

 took an examination of this island, with the intention of com- 

 paring the rocks with those of Portraine, and of investigating the 

 nature of the rock familiar to geologists under the name of 

 " Lamb.ay porphyry." The sedimentary rocks are similar to 

 some of those of Portraine, and are of ^Iiddle or Upper Bala 

 age. Associated with them are pyroclastic rocks and andesitic 

 lava- flows, some of the lavas having flowed beneath the sea. 

 The sediments and volcanic rocks were exposed to denudation, 

 and a conglomerate composed of their fragments was accumulated 

 round the volcano. The " Lambay porphyry," which has been 

 determined as a diabase-porphyry by Dr. von Lasaulx, is partly 

 intrusive in the other rocks, but has in places come to the surface 

 as a lava-flow Petrographical descriptions of the various rocks 

 were given by the authors. 



Mathematical Society, December 9. — Prof. Elliott, F.R.S., 

 President, in the chair. — Miss F. Hardcastle communicated a 

 theorem concerning the special systems of point groups on a 

 particular type of base curve. — Mr. Love, F. R.S., gave a sketch 

 of a paper, by Prof. W. Burnside, F. R.S., on "the straight line 

 joining two given points. — Impromptu communications were 

 made by Messrs. F. S. Macaulay, A. Berry, and E. T.Whittaker. 



Entomological Society, December i. — Mr. R. Trimen, 

 F.R.S. , President, in the chair. — Mr. Dudley Wright exhibited 

 an aberration of Argynnis etipkrosyne, in which the upperside 

 was suff'used with black, and the silver spots of the underside 

 of the hindwings converted into streaks. — On behalf of Mr. 

 W. H. Tuck, Mr. Tutt showed examples of Aletccciis paradoxus, 

 L. , taken in nests of Vespa mt/gari's near Bury St. Edmunds, 

 together with some of the cells in which they were found. 

 About a fifth of the nests examined were affected, some contain- 

 ing as many as twenty-four, twelve and eight examples of the 

 beetle ; the more usual number present was from two to four. 

 The dates between which examples were taken in 1897 were 

 from August 2 to October i. According to Dr. Chapman the 

 eggs were laid in the cracks of posts, <S;c. , from which the wasps 

 got the pulp to make their cells. — Combs were also exhibited 

 from nests of Vespa crabro and Vespa germanica, in which Mr. 

 Tuck had found larvse of Velleitis dilalatiis, Fabr. , which, 

 however, he had been unable to rear. — The Rev. A. E. Eaton 

 exhibited a specimen of the singular Myodites subdiplerns, 

 Fabr., taken by himself at Biskra, Algeria, and a near ally of 

 Melxctis. — Mr. Blandford called attention to a new instance of 

 the destructive propensities of Dertnestes viilpintis, Fabr. He 

 had received examples found at Hong-Kong among flags made 

 of bunting, which were presumably injured, although no details 

 had been forwarded. This form of injury was analogous with 

 the damage to woodwork recorded by himself and others ; it 

 had nothing to do with the feeding-habits of the insect, but was 

 committed by the larvte in their search for shelter in which to 

 pupate. Probably the flags had been stored at some period in 

 the neighbourhood of infested leather goods, or dried provisions. 

 The only other case of damage to textile fabrics by 

 Dertnestes vulpinus which he knew of occurred in connection 

 with the case recorded by him (Proc. Ent. Soc. Loud., 1890, 

 p. xxxi) ; a blue handkerchief spotted with white, left in the 

 infested building, was found next day to have all the white spots 

 eaten out. — Mr. Champion communicated papers entitled 

 " Notes on American and other Tingitidte, with descriptions of 

 two new genera and four species," and " A list of the 

 Staphylinidse collected by Mr, J. J. Walker, R.N., in the 

 Straits of Gibraltar." 



NO. 1468, VOL. 57] 



Paris. 



Academy of Sciences, December 6 — M. A. Chatin in the 

 chair. — On the stability of the Eiffel tower, by M. Bassot. The 

 paper is accompanied by four diagrams, showing the motion ot 

 the summit of the tower. The conclusion is drawn from these 

 curves, that to verify by periodic observations any permanent 

 displacement undergone by the summit, the measurements 

 should be taken in the evening, two or three hours before sunset, 

 as at that time the irregular movements are at a minimum. — 

 On double integrals of the second species in the theory of alge- 

 braic surfaces, by M. femile Picard. — The first modifications 

 which occur in the fixed cells of the cornea, in the neighbour- 

 hood of wounds of that membrane, by M. L. Ranvier. A 

 section is cut perpendicularly to the incisions made in the living 

 animal, and gold staining applied until the fixed cells are nearly 

 black. Those cells which have been cut by the knife at the end 

 of twenty-four hours show budding prolongations by the edges 

 of the wound. These phenomena exhibited by the cells of the 

 cornea of the rabbit are of the same order as the extension by 

 budding of the cylinder axes of cut nerve cells. — On the con- 

 tamination of wells, by M. Duclaux. By an analytical study of 

 the waters from the shallow wells of a village lately subject to a 

 slight typhoid epidemic, it is shown that a comparatively simple 

 chemical analysis suffices to distinguish between polluted and 

 unpolluted wells, provided that the composition of the water of 

 the district in a pure state is known. The bacteriological 

 method of examination is looked upon as lesstrustworthy than the 

 chemical method. — Actinometric observations made upon Mont 

 Blanc, by MM. Crova and Hansky. The measurements were 

 carried out in August and September, and were much interfered 

 with by rain. At the summit the maximum value of the solar 

 constant was 3*4, and it is suggested that under more favourable 

 conditions this magnitude might be increased to 4*0. —Observa- 

 tions on the planet (DL) Charlois (1897, November 23) made 

 at the Observatory of Toulouse (Brunner equatorial), by M. F. 

 Rossard.— Application of the method of least squares to the 

 detection of systematic errors, by M. Jean Mascart. A 

 discussion of the conditions under which the application of 

 the method of. least squares becomes illusory. — On the ap- 

 proximation of functions of large numbers, by M. Maurice 

 Hamy. — On associated pencils, by M. C. Guichard. — On the 

 focal planes of a curve plane to one or several axes of symmetry, 

 by M. P. H. Schoute. — On the existence of integrals in certain 

 diff'erential systems, by M. Riquier. Elliptical vibrations in 

 fluids, by M. V. Cremieu. — The interference in air of two 

 sound waves of different phases has been studied by observing 

 the motion of a quartz fibre placed at the point of intersection 

 of the waves. — On the dissociation and polymerisation of gases 

 and vapours. Supposed dissociation of chlorine at high tem- 

 peratures, by M. A. Leduc. The only evidence in favour of the 

 dissociation of chlorine is one isolated observation of M. Crafts 

 at 1400° C— On the electric conductivity of discontinuous con- 

 ducting substances, in relation to telegraphy without wires, by 

 M. Edouard Branly. — On the transformation of the X-rays by 

 metals, by M. G.,Sagnac. If a bundle of X-rays is allowed 

 to impinge upon a polished metallic surface, such as steel, or a 

 mercury bath, there is no appreciable regular reflexion, but rays, 

 termed by the author secondary rays, can be shown photo- 

 graphically or electrically to be diff"used from the surfaces. 

 These radiations show generally all the properties of the original 

 X-rays, but the nature of the metal is not without influence, as 

 the secondary rays from different metals can be distinguished by 

 their unequal transmission by the same substance. — Some new 

 facts observed in Crookes' tubes, by M. Virgilio Machado. — On 

 the accidental causes of irreversibility in chemical reactions, by 

 M. A. Colson. Two reactions are described in detail : the de- 

 composition of normal phosphates by hydrochloric acid, and 

 that of silver sulphate by hydrogen sulphide. In both cases 

 secondary reactions intervene, which render the reversibility of 

 the phenomena impossible. — On the existence of a cuprous 

 sulphate, by M. A. Joannis (see p. 159). — On the elementary 

 unity of the body called cerium, by MM. Wyrouboff and A. 

 Verneuil. A criticism of the results of M, Boudouard, whose 

 atomic weight determinations are stated to be affected both by im- 

 purities in his material, and inaccuracy in experimental work. — 

 On aldehyde ammonia, by M. Marcel Delepine. Aldehyde 

 ammonia, when left for three days in a vacuum over sulphuric 

 acid, loses water, giving brilliant white crystals of a new base, 

 ethylidene-imine, which analysis and cryoscopic estimations 

 show to have the formula (CH3- CH = NH)3. A solution of 



