May 2 2, 1890] 



NATURE 



91 



map suspended in the same room.— (2) Series of specimens 

 illustrating the dynamical metamorphism of rocks. This case 

 contained an important collection of specimens from Switzerland, 

 Norway, and Scotland, illustrating some of the more remarkable 

 eftects of the mechanical deformation and recrystailization of 

 rocks. The first series was one of specimens of Triassic and 

 Jurassic dolomites and limestones from Canton Glarus, showing 

 the extraordinary manner in which these rocks have been squeezed 

 and puckered. Attention was particularly directed to the evidence 

 afforded by the fossils [Belcmiiites) of the extent to which the 

 strata have been stretched in some parts. The second series, 

 from the south of Bei^en, showed the presence of recognizable 

 Silurian corals and trilobites in rocks which have been so much 

 metamorphosed as to have acfjuired the characters of finely 

 crystalline phyllite or micaceous schist. The third series, 

 from the north-west of Scotland, illustrated how a massive 

 quartzite, full of annelide-tubes, has been crushed and recrystal- 

 lized until it has assumed the structure of a quartz-schist, and all 

 trace of the fossils has been obliterated. The effects of 

 mechanical movements even among the comparatively young and 

 soft rocks of the south of England were illustrated by two speci- 

 mens placed in this case from the under-surface of a " thrust - 

 plane " in the vertical chalk of the Dorsetshire coast. They 

 showed how the chalk has been indurated, smoothed, and polished 

 by the movement of the overlying mass. A view and s-ection of 

 this thrust-plane were |>laced beside the specimens. 



Specimens of minerals brought from Ceylon by C. Barrington 

 Brown, exhibited by Prof. J. W. Judd, F.R.S. Large perfectly 

 crystallized and clear beryl, 2650 grammes in weight. The 

 specimen, though water-worn, exhibits the crystalline form. 

 The colour is intermediate between that of emeralds and 

 aquamines. The specific gravity is 2703. Fine crystal of 

 yellow corundum (oriental topaz). Well developed crystals of 

 corundum (sapphires, &c.). Crystal of chrysoberyl from the 

 same district. 



Maps to illustrate magnetic surveys of special districts in the 

 United Kingdom, exhibited by Profs. Riicker and Thorpe, 

 FF.R.S. The arrows represent the horizontal disturbing forces 

 in magnitude and direction. The figures give the vertical 

 disturbing force in terms of ooocxji C.G.S. units, taken as 

 positive when it acts downwards. In some maps, regions of 

 great (downward) vertical force are indicated by deeper tints. 

 Map I. Indications of an attracting centre at sea, to the south of 

 the Hebrides. Map 2. Horizontal disturbing forces at stations 

 near the boundaries of a district in Yorkshire and Lincolnshire, 

 within which there is a locus of attraction. Map 3. Regions of 

 high vertical force within the above district. The highest 

 observed values are at Market Weighton and Harrogate. Map 

 4. Ridge line or locus of attraction drawn (continuous line) by 

 connecting stations of maximum vertical force, and (dotted line) 

 by connecting points midway between the stations at which the 

 direction of the horizontal force disturbance changes. Map 5. 

 Ridge line, 150 miles long, probably correct to within five miles 

 for the greater part of its length. 



Mr. C. V. Boys, F.R.S., exhibited :—(l) Oscillating spark 

 experiment. This is a modification of the method employed by 

 Dr. Lodge to show the oscillatory nature of a spark formed 

 under proper conditions. Six lenses are mounted on a disk, 

 and are made to rotate. Each forms upon a screen an image 

 of the spark, which is drawn out by the movement of the lens 

 into a broken band of light. The lenses are not exactly 

 the same distance from the axis, so that the band formed by 

 one is not overlapped by the band formed by the next. 

 Thus the whole duration of the spark from the first to 

 the last oscillation may be observed or photographed, 

 —(2) Photographs showing the formation of drops. Water 

 drops, half an inch or more in diameter, were allowed to slowly 

 form and break away in a liquid of slightly lower specific gravity — 

 namely, a mixture of paraffin and bisulphide of carbon. Photo- 

 graphs of these were taken as follows : they were illuminated by 

 an electric arc and large condensing lenses, a camera was placed in 

 front, and the view was rendered intermittent by a card disk with 

 one hole near the edge made to rotate at from fourteen to twenty 

 turns a second. The exposure was about one eight -hundredth 

 of a second. Fortv inches of photographic plate were arranged 

 in a long slide which could be drawn past by hand. Three of 

 these multiple photographs are exhibited. The thaumatrope was 

 made by sticking the separate parts of the last series round a 

 card disk, and afterwards painting the surface black and white, 

 following the outlines of the photographs exactly. The thauma- 



trope clearly shows the gradual formation of the drop and the 

 spherule, the oscillation of the pendant drop immediately after- 

 wards, the rebound of the spherule from the pendint drop, the 

 oscillation of the large drop as it falls, and its rebound from the 

 water below into which it fell. Other photographs are shadows 

 of water jets cast upon a photographic plate by the action of a 

 small distant spark, a method invented by Mr. Chichester Bell. 

 The remainder are photographic shadows cast by a water jet 

 upon a rapidly moving plate by the intermittent light of an 

 oscillating spark. These clearly show the movement of the 

 separate water drops. 



Sugar-cane {Saccharuin officinaritm) seed and seedlings, 

 exhibited by Mr. D. Morris. There appears to be no authentic 

 record of any really wild station for the sugar-cane, and the fruit 

 has not hitherto been figured or described. At Barbados, 

 several times during the last twenty years, and more recently by 

 Prof Harrison and Mr. Bovell, self-sown seedlings of the sugar- 

 cane have been observed. The subject was taken up system- 

 atically in 1888, and about sixty of the seedlings raised to mature 

 canes. Many of these exhibited well-marked characteristics 

 differing from the varieties growing near them. Careful inquiry 

 has shown that canes known as the " purple transparent " and 

 "white transparent," and possibly also the "Bourbon" cane, 

 produced seeds in very moderate quantities. Spikelets received 

 at Kew have been examined and the seed found /;/ situ. It is 

 anticipated that, by cross-fertilization and a careful selection of 

 seedlings, it will now be possible to raise new and improved 

 varieties of sugar-cane, and renew the constitutional vigour of 

 plants that have become deteriorated through continuous cultiva- 

 tion by cuttings or slips. Great importance is attached to the 

 subject in sugar-producing countries, as it opens up an entirely 

 new field of investigation in regard to sugar-cane cultivation. 



Prof. H. Marshall Ward, F.R.S., exhibited a selection of 

 transparent photographs, showing (i) the habits, &c., of various 

 trees from different parts of the world ; (2) the comparative 

 structure and anatomy of several European timbers ; and (3) some 

 of the more prominent features of diseases of wood, &c., and 

 fungi causing them. 



The electrification of a steam jet, exhibited by Mr. Shelford 

 Bidwell, F. R. S. The shadow of a small jet of steam cast upon 

 a white wall is, under ordinary conditions, of feeble intensity and 

 of a neutral tint. But if the steam is electrified, the density of 

 the shadow is at once greatly increased, and it assumes a peculiar 

 orange-brown hue. The electrical discharge appears to promote 

 coalescence of the exceedingly minute particles of water contained 

 in the jet, thus forming drops large enough to obstruct the more 

 refrangible rays of light. It is suggested that this experiment 

 may help to explain the intense darkness, often tempered by a 

 lurid yellow glow, which is characteristic of thunder-clouds. See 

 Phil. Mag., Feb. 1890, p. 158. 



Mr. Killingworth Hedges exhibited : — (i) Gramme dynamo 

 worked as a motor, fitted with bearings of a new carbon compo- 

 sition, which does not require oil for lubrication. — (2) Vortex 

 speed indicator, driven by the above, fitted with oilless bearings. 



Lord Rayleigh, Sec.R.S., exhibited :— (l) An instrument for 

 testing colour vision. — (2) Polarization of light by chlorate of 

 potash crystals. 



Photographs of eggs of the Great Auk, exhibited by Mr. 

 Edward Bidwell. There are 67 recorded eggs of this extinct 

 bird, of which 45 are in Great Britain. The collection of photo- 

 graphs exhibited consists of two views each of 53 of these eggs, 

 photographed to scale. 



Specimens of Simony's Lizard (Lacaia slmoityi), from the 

 lonely rock of Zalmo, near the Island of Ferro, Canaries, ex- 

 hibited by the Zoological Society of London. A rare lizard, 

 only known from this spot, and said to feed on crabs. These 

 lizards were obtained by Canon Tristram, F.R.S., during his 

 recent visit to the Canaries, and presented to the Zoological 

 Society by Lord Lilford. 



Electric-radiation meter, for obtaining quantitative measure- 

 ments of the intensity of the radiations emitted by an electric 

 oscillator, exhibited by Mr. Walter G. Gregory. Its action is 

 based on measuring the increase of length of a stretched wire, or 

 strip of metal, when heated by the currents induced in it by the 

 rapidly varying field of force. In the instrument exhibited, the 

 elongation of a fine platinum wire is shown by atlcching to one 

 end of it a fine helical spring made by winding a tlin metallic 

 ribbon round a cylinder. As the wire extends tie spring 

 rotates, and the motion is further magnified by a small mirror 

 which reflects the image of a wire on a scale. The oscillator is 



NO. 1073, ^'OL. 42] 



