May 27, 1922 



NATURE 



693- 



The Royal Society Conversazione. 



''PHE first of the two annual conversaziones of 

 A the Royal Society was held at Burlington 

 House on May 17, when Sir Charles Sherrington and 

 tlie officers of the Society received the fellows and 

 quests. A few of the exhibits were shown last 

 \ car, and it is an invidious task to select some of 

 I lie remainder for mention. We have therefore 

 grouped the exhibits on related subjects and propose 

 to describe briefly a few of the items in each group. 

 ' Sir Almroth Wright demonstrated methods of 



measuring the bactericidal potency of the blood 

 fluids and leucocytes. With regard to the microbes 

 that give rise to " blood poisoning " and septicaemia, 

 the capacity for growing in the blood fluids depends 

 on capacity for overcoming the normal anti-tryptic 

 power of the blood and digesting its albuminous 

 substances. Increased destruction of microbes can 

 be obtained by the vaccination of the blood in vitro. 

 This is important, for where the patient is unable to 

 respond to a vaccine he can be transfused with a 

 normal blood which has by vaccination in vitro 

 been furnished with the protective substances 

 required. The lysozymic action of tissues and 

 secretions was demonstrated by Dr. Alexander 

 Fleming. This inhibitory effect on bacteria is so 

 strong that with tears diluted i in 100 it is complete 

 in a few seconds, and it is shown even with tears diluted 

 I in 5,000,000 or egg white diluted i in 50,000,000. 



Specimens of giant frogs were exhibited by the 

 Department of Zoology, Natural History Museum 

 (Mr. C. Tate Regan). Rana goliath, from S. Cameroon, 

 is the largest known frog, attaining a length of nearly 

 1 2 inches, without the limbs. Rana guppyi, from the 

 Solomon Islands, is remarkable in that it feeds almost 

 exclusively on crabs, which are swallowed whole. 



Some results of researches on the biology of 

 aphides, with particular reference to Aphis rumicis, 

 were illustrated in the exhibit of the Entomological 

 Department, Institute of Plant Pathology, Rotham- 

 sted (Dr. A. D. Imms and Dr. J. Davidson). Breed- 

 ing experiments have shown the relationship between 

 the agamic and gamic generations, and the appear- 

 ance of winged and apterous forms ; the changes 

 associated with these phases are due to internal factors. 

 Variations occur in the same species on different 

 plant hosts. 



Internal casts of a gigantic freshwater gastropod 

 from Wealden Rocks, near Silver Hill, Hastings, 

 were exhibited by the Department of Geology, 

 British Museum (Natural History). Twenty-three 

 whorls, including the body-whorl, are traceable, 

 with a total length of 7 ft. 3 in. The affinities of the 

 mollusc are probably with the Tiaridae. 



Astronomy was represented by exhibits from the 

 Royal Observatory, Greeawich. Photographs with the 

 30-inch reflector were used to show a relation between 

 the effective wave-lengths of stars and their spectral 

 type. When a coarse grating is placed before an object- 

 ive, short diffraction spectra are produced in the focus 

 <Mi either side of a central image, the distance between 

 the diffracted and central images being a function of 

 I lie wave-length of the light. This furnishes a con- 

 \enient means for determining the colours of the 

 stars as defined by the wave-length of maximum 

 photographic intensity. A chart of variation of 

 latitude at the observatory during 1911-1921 was 

 also shown. The curve can be analysed into two 

 principal components, one with a period of 432 days, 

 and the other with a period of one year. The 

 amplitude of the first component is about twice that 

 of the second, 



NO. 2743, VOL. 109] 



Sir William Bragg and Prof. W. L. Bragg exhibited 

 a number of models, on a scale of 10* : i, illustrating 

 crystal structure. By X-ray analysis, the size of the 

 cell containing the unit of pattern of the crystal is 

 found accurately. The distance between the centres 

 of neighbouring atoms is also known and accurate 

 models can be constructed which, in the case of 

 organic crystals, are based on the principle that 

 benzene and naphthalene molecules are frameworks 

 of definite dimensions. 



Prof. H. B. Baker gave a demonstration of the 

 changes produced by prolonged drying on the boiling- 

 points of liquids. Dried benzene does not boil when 

 immersed in boiling water, and other liquids including 

 mercury, bromine, alcohol, and ether show a rise in 

 boiling-point which varies from 26° to 62° C. The sur- 

 face tension also increases, indicating that the change 

 may be due to increase in the size of the molecules. 



The National Physical Laboratory had a number 

 of exhibits. A precision bridge for platinum ther- 

 mometry designed by Mr. F. E. Smith was shown by 

 Mr. W. F. Higgins and Mr. F. H. Schofield. The 

 resistances of the two variable arms of the bridge 

 system used are of the order of 100 times that of the 

 thermometer, so that brush contacts can be used 

 without appreciable sacrifice of precision. The 

 steps on the lowest dial correspond to o-ooi° C. 

 The Research Department, Woolwich, Radiological 

 Branch, exhibited a metal X-ray tube of novel form, 

 with an iron target. The tube is of the hot cathode 

 type, and is constructed chiefly of metal, the insula- 

 tion between the anode and the case being secured 

 by a glass sleeve. Both the anode and the metal 

 case are water-cooled. The tube is self-shielding, 

 only a narrow pencil of X-rays escaping from un 

 aluminium window. It is designed to give very soft 

 radiations, and to run continuously with a heavy 

 current. The Cambridge and Paul Instrument Com- 

 pany, Ltd., showed a micro - indicator for taking 

 diagrams from high-speed engines. The vertical 

 movement of the end of a small indicator piston 

 deflects a strong triangular spring carrying a stylus 

 which scratches a micro-diagram of a single com- 

 plete cycle upon a disc of transparent celluloid. The 

 actual size of the diagram is approximately 3 mm. 

 base (time) by 2J mm. height (pressure). 



Mr. W. M. Mordey demonstrated some 'striking 

 effects of alternating magnetism. Magnetic materials, 

 including finely divided iron, nickel, cobalt, magnetite 

 and specular haematite, show a steady movement or 

 migration through or from a multiphase field in a 

 direction opposite to that due to eddy currents. 

 In a multiphase field vertical " planes of force " 

 are formed, but there is no movement of finely 

 divided aluminium nor lead shot. Water containing 

 any of these materials may be driven uphill in a 

 multiphase field, an effect which is probably due to 

 surface-tension. The method can be applied to the 

 concentration or separation of certain minerals, 

 wet or dry (Nature, April 29, p. 556). 



During the course of the evening Lord Rajdeigh 

 gave an account of his recent spectroscopic investiga- 

 tions of the aurora borealis, with particular reference 

 to its occurrence on ordinary nights in the South of 

 England. 



It is impossible in the space of a short article to do 

 more than indicate some of the many interesting and 

 important exhibits which were displayed. There were 

 several novel pieces of physical and electrical apparatus 

 which have not been mentioned, and the whole com- 

 bined to form a noteworthy and interesting display. 



