92 



NA TURE 



[May 2 2, 1890 



•of the usual type, and is worked by an induction coil and four 

 accumulators, the latter kindly lent by the Electric Construction 

 Corporation. 



Breath figures, showing that polished surfaces placed near to 

 bodies in low relief often take an impression of the detail, which 

 is made visible by breathing upon the surface (the period of ex- 

 posure varying in different circumstances), exhibited by Mr. W. 

 B. Croft, (i) A coin is lightly pressed on a freshly split surface 

 of mica for 30 seconds; the mica takes a breath figure of the 

 detail of the coin. (2) Paper printed upon one side has lain for 

 10 hours between two plates of glass ; the print appears in white 

 letters on both. Part of this phenomenon, although not with 

 print, was noticed by Moser in 1840. (3) Sometimes the print 

 appears in black letters ; the same impression may change from 

 white to black. (4) Coins are put on the two sides of a piece 

 of glass and electrified for two minutes ; each side has a perfect 

 impression of that side of the coin which faced it. An electro- 

 type plate may be reproduced in a similar way. These effects 

 were partly indicated by Karstens in 1840. (5) An electric 

 spark is sent across glass. Five superposed bands appear, 

 black and white, of decreasing breadths, as well as three per- 

 manent scars. Riess, 1840. (6) The microscope shows water 

 particles over the whole surface, larger or smaller as the effect is 

 black or white. 



Prof. Silvanus P. Thompson exhibited : — (i) Optical rotator. 

 This apparatus is for rotating the plane of polarization of light, 

 and is intended to be used in conjunction with polarizing re- 

 flectors (black-glass mirrors, &c.), which do not admit of being 

 bodily rotated around the axis of the beam of light. The prin- 

 ciple of the new rotator consists in the employment of two 

 quarter-wave plates of mica, one of which is fixed at 45° across 

 the plane-polarized beam of light, which it thus converts into 

 circularly-polarized light. The second quarter-wave plate, 

 which can be rotated by a simple gear, reconverts the circularly- 

 polarized beam into plane-polarized light, vibrating in any de- 

 sired azimuth. (Constructed by Messrs. Newton and Co.) — 

 {2) Natural diffraction-grating of quartz. This specimen of 

 iridescent quartz exhibits ditfraction-spectra corresponding to 

 those of a grating ruled to 12,000 lines to the inch. A micro- 

 photograph taken by Mr. C. L. Curteis, with a Reichert's 

 apochromatic (3 mm.) lens, shows the nature of the minute 

 structures of the specimen. For the sake of comparison, a 

 diffraction-grating of 6000 lines to the inch, photographed on 

 glass, is exhibited beside the piece of quartz. — (3) New straight- 

 vision prisms, consisting each of a single prism of Jena glass, of 

 very wide angle, immersed in cinnamic ether. The materials 

 having identical mean refractive index, rays of mean refrangi- 

 bility pass straight through. (Constructed by Messrs. R. and 

 J. Beck.) — (4) Colour experiments. Two liquids, incapable of 

 mixing, are placed over one another in a flat bottle. They are 

 chosen so that each absorbs all the rays that the other one can 

 transmit. Though each is transparent, they are jointly abso- 

 lutely opaque. They are also opaque when shaken up together. 

 Experimental illustration of the recent investigations of M. 

 Osmond on molecular changes which take place during the cool- 

 ing of iron and steel, exhibited by Prof. W. C. Roberts-Austen, 

 F.R.S. In the case of mild steel, containing 05 per cent, of 

 carbon, as it cools down from a temperature of 1100° C, two 

 points may be observed at which heat is evolved. The first of 

 these occurs at 750° C, and marks the change of /S (or hard) 

 iron to o (or soft) iron. The second evolution of heat is ob- 

 served at 660°, and is due to a change in the relation of the 

 carbon and iron. M. O.-mond, in continuing an investigation 

 made by Roberts-Austen, has shown that the presence in iron of 

 elements with small atomic volumes retards the change of 3 to o 

 iron, and, conversely, elements having large atomic volumes 

 hasten the change. 



Specimen of phosphorous oxide, and apparatus for preparing 

 same, exhibited by Prof. Thorpe, F. R. S., and Mr. Tutton. 

 This substance has been shown by the exhibitors to be repre- 

 sented by the formula P40g. It crystallizes in monoclinic prisms 

 melting at 25°'5, and boils in an atmosphere of nitrogen or car- 

 bon dioxide at 173°. Cold water dissolves it with extreme slow- 

 ness, forming phosphorous acid. With hot water, strong caustic 

 alkalies, chlorine, bromine, and alcohol it reacts with great 

 energy, generally with inflammation. Oxygen slowly converts 

 it, at ordinary temperatures, into phosphoric oxide, and under 

 diminished pressure the combination is attended with a faint 

 lurhinous glow similar to that observed in case of phosphorus. 

 No ozone, however, is formed. At slightly higher temperatures 

 ihe oxidation is brought about instantly with production of 

 NO. 1073, "^OL. 42] 



flame. Phosphorous oxide possesses the smdlusually attributed 

 to phosphorus, and which is identical with that noticed in match 

 manufactories. It is highly probable, as Schiinbein surmised, 

 that the element phosphorus is without smell, and that the smell 

 ordinarily perceived is due to a mixture of orone and phosphor- 

 ous oxide. Phosphorous oxide is highly poisonous, and it is 

 not improbable that phosphorus necrosis is caused by this 

 substance. 



Photographs of the spectrum of the nebula in Orion, exhibited 

 by Prof J. Norman Lockyer, F.R.S. These photographs were 

 taken in February with the 30-inch reflector at Westgate-on- 

 Sea, the exposures varying from 2 to 3 hours. The one taken 

 with a 3 hours' exposure (February 10) shows about 50 lines 

 between A 500 and A 373, but many of them are only visible 

 with difficulty, especially in artificial light. The Henry Draper 

 Memorial photograph of the spectrum of P Cygni was shown for 

 comparison, and it was seen that all the bright lines were 

 amongst the brightest in the nebula. This argues in favour of 

 the view that stars with bright-line spectra are of a nebulous 

 character. • 



Photograph of the two clusters (33 and 34 lj[ VI.) in the 

 sword-handle of Perseus, showing remarkable coronal and '■ 

 festoon-like groupings amongst the stars on several parts of the 

 photograph, exhibited by Mr. Isaac Roberts. These clusters ti 

 are quite free from nebulosity, and in this respect they differ * 



from other clusters which Mr. Roberts has photographed ; for 

 those clusters are involved in faint but distinct nebulosity. 



The larvae of Amphioxus, exhibited by Prof. E. Ray Lan- 

 kester, F.R.S. 



A selection from the butterflies collected in the great equa- 

 torial forest of Africa by Mr. William Bonny, one of Mr, 

 Stanley's staff, exhibited by Mr. Henley Grose- Smith. Little 

 was known of the Lepidoptera of this part of Africa ; few of the 

 species collected by Mr. Bonny have been previously recorded 

 from that region, and nine are new to science. The collection 

 includes, amongst others, the great Papilio anlimachus, also 

 Papilio zalmoxis, and many West African species. 



Collection of iridescent crystals of chlorate of potash to illus- 

 trate the production of colour and its intensification by reflection 

 from multiple thin plates, exhibited by Dr. Alex. Hodgkinson. 



Dr. Alexander Muirhead exhibited : — (i) Some patterns of 

 Dr. Lodge's lightning protector for cables and for telegraphic 

 work generally. In these instruments a series of air-gaps, sepa- 

 rated by self-induction coils, are offered to the lightning, or 

 other high-tension currents, which have got into the line. The 

 greater part of the flash jumps the first air-gap, most of the 

 residue jump the next, and so on, until after four or five dilutions 

 nothing is left which can break down the thinnest insulation, or 

 appreciably affect even a delicate galvanometer connected to the 

 protected terminals. — (2) Muirhead's portable form of the Clark 

 standard cell, in cases, with thermometer. — (3) Standard con- 

 denser, i microfarad (with Dr. Muirhead's certificate). — (4) Set 

 of Thomson and Varley slides, small. — (5) Saunders's capacity 

 key, suitable for Dr. Muirhead's capacity test. — (6) Saunders's 

 reversing key. 



Specimens of aluminium and alloys manufactured by the 

 Aluminium Company, Limited, exhibited by Sir Henry E. 

 Roscoe, F.R.S. Pigs of aluminium, 99 per cent. pure. Cast- 

 ings in aluminium, rough and finished. Specimens of aluminium, 

 soldered. Aluminium wire, sheet and drawn rod. Aluminium 

 medals, plain and gilt. Cast aluminium bronze and brass, show- 

 ing {a) tensile strength and elastic limit ; {b) twisting stress ; {c) 

 thrusting stress, long specimens ; [d) thrusting stress, short speci- 

 mens. Stampings in aluminium bronze, rough. Ten per cent, 

 aluminium bronze, twisted cold. Five per cent, aluminium 

 bronze, worked hot and cold. Aluminium brass, worked hot 

 and cold. Aluminium bronze and brass sheet. 



Specimens illustrating ancient copper and bronze from Egypt 

 and Assyria, exhibited by Dr. Gladstone, F.R.S. The collec- 

 tion consists of borings from tools found by Mr. Flinders Petrie, 

 at Kahun, in Egypt, and which belong to the XII. Dynasty — 

 about B.C. 2500 ; also from other tools found at Gorub, which 

 belong to the XVIII. Dynasty — about B.C. 1450. There are 

 also fragments of Egyptian bronze figures from Bubastis, and of 

 Assyrian bronze from the gates of the Palace of Shalmanezer II., 

 at Balawat— about B.C. 840 ; as well as two pieces of slag from 

 the old copper mines of the Sinaitic Peninsula, which were 

 worked by the Egyptians in very early times, and discontinued 

 after the XVIII. Dynasty. The principal point illustrated is 

 the fact that the earliest metal implements were of copper, con- 

 taining a very little arsenic and tin, probably as accidental im- 



