NA TURE 



[June 27, 1907 



Durini* the lonfcrcnce Ihc menihcrs had the privilege 

 of visiting iTiaiiy wortcs and generating stations, and these 

 opporlunitjes were talcen advantage of to a large extent. 

 The institution conversazione was held on Thursday even- 

 ing in the Albert Hall, when a large and representative 

 gathering met for social intercourse. 



THE ROYAL SOCIETY CONVERSAZIONE. 

 A/rOST of the e.xhibits of scientific interest at the Royal 

 Society on June 19, on the occasion of the soiree 

 to which ladies as well as gentlemen are invited, were 

 shown at the conversazione on May 8, and have been 

 described already in Nature (May i(), p. 57). It will be 

 sutTicient, therefore, to refer briefly to exhibits not 

 mentioned in the previous article. 



Lantern and other denionstrations were given during 

 the evening by Prof. H. A. Micrs, Prof. Flinders Petrie, 

 and Mr. Louis Brennan. Prof. Miers showed experiments 

 illustrating the growth of crystals in drops of solution, and 

 indicating that the latter are of two sorts. If a solution be 

 sufficiently strong, crystallisation may be started spon- 

 taneously by mere shaking or friction. In such a solution 

 the crystals are apt to grow rapidly in the form of delicate 

 needles and fronds. If the solution be supersaturated, but 

 not strong enough to give birth to crystals in this way, 

 they can only grow if introduced from without (by 

 ■■ inoculation " of the drop), and are apt to grow in 

 symmetrical forms. .-^ solution, as it cools, passes quite 

 suddenly from the one state to the other. Prof. Petrie 

 lectured on houses in ancient Egypt, and Mr. Brennan 

 again showed and described his working model of the 

 Brennan mono-railway. 



The subjoined descriptions of the exhibits have been 

 abridged from the official catalogue : — 



Mr. .4. .1. Campbell Swintoii : Vacuum tube phenomena, 

 (i) Exhibition of the mechanical effects of kanal rays in 

 causing the rotation of mill-wheels in Crookes tubes. 

 These rays, which are positive, travel in the opposite 

 direction to the negative rays that proceed from the 

 kathode. They can be detected both when they are 

 approaching the kathode, and also, if the latter is per- 

 forated, after they have passed through the apertures. 

 (2) Photomicrographs of the bubbles that are developed by 

 sudden heating of portions of the glass walls of Crookes 

 tubes, owing to the occlusion. by the glass of the residual 

 gas during prolonged use. (3) Exhibition in the micro- 

 scope of a special case of the above, in which the sudden 

 heating was occasioned by an electric spark, which has 

 thus impressed its own image on to the glass. The image 

 is entirely made up of minute bubbles, and from its form 

 it is clear that the spark was a positive one. — Mr. C. E. S. 

 Phillips: (i) A fibre electroscope. In this electroscope the 

 gold leaf is replaced by a fibre of electrically conductive 

 glass which is delicately hinged so as to move very readily 

 under the influence of a difference of potential. (2) An 

 electroscope charger. The ease with which celluloid may 

 be electrified by friction, together with its poor insulating 

 properly, are made use of in this apparatus. A celluloid 

 rod is rubbed at one end by a flannel-lined split brass 

 tube. The charge so produced slowly spreads to the 

 opposite extremity of the rod and is there utilised. Either 

 a positive or negative charge may be obtained with the 

 same instrument. (3) Electrically conductive glass. The 

 composition of this glass is as follows : — sodium silicate, 

 thirty-two parts; borax, eight parts; Powell's flint glass, 

 i'25 parts. The electrical conductivity is about 500 times 

 as great as that of any other glass, and this material is 

 suitable for the windows of electrostatic instruments as 

 well as for supplying the fibres used in the fibre electro- 

 scope. — Mr. ]. Mackenzie Davidson ; Stereoscopic X-ray 

 photographs in a revolving lenticular stereoscope. A 

 single X-ray photograph is a central projection shadow of 

 (he object placed between the Crookes tube and the photo- 

 graphic plate, and cannot therefore correctly indicate the 

 real relative position of the parts — but stereoscopic X-ray 

 photographs at once give a combined image which shows 

 correctly their relative size and position. This could be 

 observed in the series of transparencies exhibited. — Mr. A. 



NO. 1905. VOL. 76] 



Kershaw : .\ new visual method of measuring the speeds 

 of photographic shutters. This consists principally of a 

 variable-speed revolving disc with radial slits, in con 

 junction with a stationary illuminated slit. — Mr. Edward 

 H'liymper ; Photographs taken in the Rocky Mountains of 

 Canada and in the Alps. 



.Mr. William Burton: Pilkington's Lancastrian lustre 

 pottery. The examples illustrate the perfecting of the old 

 lustre process of decoration. By this method metallic 

 vapours of silver and of copper can be driven into pottery 

 glazes at a very low red heat under the influence of re- 

 ducing gases. The surface of the metallic film so obtained 

 glows with brilliant iridescent colours. The process has 

 been reduced to such precision that the kilns are 

 hermetically sealed during the firing, and no " trials " of 

 any description are drawn from start to finish of the 

 process. The temperature is recorded by the use of two 

 thermocouples, placed at the bottom and top of the kiln 

 respectively. The reducing gases are of standard com- 

 position, so that the process is so far as possible auto- 

 matic. — Hon. C. .4. Parsons, F.R.S. : Photographs of 

 diamonds obtained from pure iron heated in a carbon 

 crucible in an electric furnace and rapidly cooled. Scale, 

 150 diameters. — Dr. Herbert Smith: Precious stones, cut 

 and uncut. The exhibit includes most of the mineral 

 species that are available for jewellery purposes. The 

 following are the more noteworthy of the specimens : — a 

 star-twin of diamond ; crystals and faceted specimens of 

 olivine (peridot) from the Red Sea ; sapphires from 

 Montana and Ceylon ; natural and " reconstructed " rubies ; 

 various opals, including opalised shells ; diamonds, chryso- 

 beryls, and topazes from Rhodesia ; garnets from German 

 East Africa ; and specimens of the rare species phenakite, 

 axinite, and diopside. — Dr. Tempest Anderson : Photographs 

 illustrative of the volcanoes of Central America, and of a 

 revisit to the Soufriere of St. \'incent. The volcanoes of 

 the Soufriere of St. Vincent and Montagne Pelee in 

 Martinique, both to the east of the Caribbean Sea, erupted 

 in 1902. The volcano of Santa Maria in Guatemala, to 

 the west of the same sea, erupted in the same year, and 

 when it was examined this spring the eruption proves to 

 have been of the same character. I 



The Royal Society : The Linnaeus bicentenary-»-original 

 certificate of candidature of Linna;us. dated 1753, for 

 election into the Royal Society. — Dr. IT. .4. Ciinnington 

 and Mr. C. L. Botilenger : Examples of the fauna of the 

 Fayiim Lake, Birlcet-Qurun, investigated at the request 

 of the Egyptian Survey Department. (i) Series of the 

 fishes, including examples of the three different kinds of 

 Bulti (Tilapia). The females take charge of the eggs and 

 young, which they seclude in the mouth and gill-chambers. 

 (2) .Series of the invertebrates of the lake, including 

 examples of a new lacustrine medusa (Mocrisia lyonsi). — 

 Prof. Charles Stci.vart, F.R.S. : (i) Specimens illustrating 

 alternation of generation. (2) Various invertebrates and 

 birds showing colours due to structure; mostly thin films, 

 and not pigment ; consequently the colour is lost on crush- 

 ing. — Prof. S. J. Hickson, F.R.S. : A collection of species 

 of the genus Corallium, and a specimen of Coralliiini ' 

 maderense, polished and mounted in silver. — Dr. Ernst 

 Hartert : Birds represented in the British Isles by peculiar | 

 forms, and their Continental allies. So late as 1802 \ 

 Wallace accepted only three birds as peculiar to the British 

 Isles (" Island Life," p. 340), and even more recent works 

 have not mentioned more than three or four. Careful 

 investigations, however, have shown that about twenty 

 British birds show constant and often easily recognised 

 differences from their Continental allies. Eighteen of these 

 are exhibited, with their allies, in order to show their 

 differences. 



Prof. Flinders, Pelrie, F.R.S. : Pottery soul-houses. 

 3000 B.C. These models, made by the Egyptians, were 

 found at the cemetery of Rifeh in Upper Egypt, where 

 they had been placed upon the graves. They were 

 developed from the trays of offerings for the dead, to 

 which a shelter was added, and further enlarged with the 

 addition of furniture so as completely to resemble an actual 

 house, in which the soul was supposed to dwell. Their, 

 period is from the ninth to the twelfth dynasty. Foun' 

 by the British School of .'Vrchxology in Egypt, 1907. 



