470 



SCIENTIFIC NEAVS. 



[May i8, i8 



variety of interesting observations and experiments may 

 be made upon leaves or flowers, which present some 

 peculiarities of colouration. 



Some account of the physiological relations of chloro- 

 phyll will be found in an article on " The Green Colouring 

 Matter of Plants," which appeared in Scientific News, 

 page 85. 



THE ROYAL SOCIETY'S CONVERSA- 

 ZIONE. 



TT is customary for the President and Council of the 

 Royal Society to hold two conversazioni each year, 

 the first being in May, when gentlemen only are admitted, 

 and the second in June when ladies are also present. On 

 these occasions an interesting exhibition of the latest 

 scientific instruments is arranged in the spacious rooms 

 of the Society at Burlington House. The first conversa- 

 zione of this season was held on Wednesday evening, 

 the 9th instant, and was very numerously attended by 

 representatives of every branch of science. 



Mr. Wimshurst exhibited his large electrical influ- 

 ence machine, which has 12 discs of 2 feet 6 inches 

 diameter, each carrying 16 metal sectors. This instru- 

 ment showed large and perfect brush discharges at its 

 terminals, and with Leyden jars gave sparks 13^ inches in 

 length. Prof. Riicker conducted a number of experiments 

 on the optical demonstration of electrical stress. Con- 

 ductors of various forms are immersed in bisulphide of 

 carbon, and placed between Nicol's prisms. When the 

 conductors are oppositely electrified, the medium is 

 thrown into a state of stress, and the light which had 

 been extinguished by the analysing prism is restored. 

 Captain Abney and Major-General Testing exhibited an 

 instrument to measure the light reflected from coloured 

 pigments. 



Mr. Boys made a number of very beautiful experiments 

 with soap-bubbles. By blowing a bubble inside another 

 he showed the power of an air film to prevent the two 

 bubbles from coming into real contact, even if the outer 

 one be pulled out until it squeezes the inner one into a 

 long oval. An inner bubble filled with coal gas carried 

 up to the ceiling an outer one to which was attached a 

 wire ring and a piece of string without really touching it 

 at all. Some of the experiments showed the effects of 

 diffusion, of vibration, and of electricity upon bubbles and 

 groups of bubble. Mr. Boys also exhibited his radio- 

 micrometer, which is the most delicate instrument yet 

 made for measuring radiant heat. 



Prof Judd showed numerous specimens and sections 

 illustrating the recent borings in the delta of the Nile, 

 which reveal some facts of great geological interest. The 

 alternations and mixtures of blown sand and Nile allu- 

 vium were found to continue down to the depth of 121 

 feet from the surface and 95 feet below the level of the 

 Mediterranean. At that depth a remarkable change in 

 ihe deposits took place, and beds of gravel containing 

 both pebbles and sub-angular fragments of quartzite, 

 chert, compact limestone, with some metamorphic and 

 igneous rocks, were found ; and similar beds occur at 

 intervals down to the greatest depth reached. Mr. 

 Gardner exhibited some very fine fossil plants from a 

 small patch of limestone beneath the gravels and silts of 

 an old river course sealed up in the great trap flows of 

 Western Scotland ; the Director-General of H.M. Geo- 

 ogical Survey showed several maps and diagrams illus- 

 rative of the recent work of the geological survey in the 



north-west Highlands ; and Mr. Cadell exhibited some 

 photographs illustrating experiments in mountaiii 

 building. 



Mr. Symons showed a set of thermometers which had 

 been specially constructed for his use in determining the 

 present temperature of the mineral springs in the 

 Pyrenees, and also a number of views in the neighbour- 

 hood of these springs, etc. Mr. Chaney exhibited two 

 standard thermometers of the new form approved by 

 the Comite Internationale des Poids et Mesures. These 

 are 700 mm. long, and 28 grammes in weight; they are 

 graduated from o degs. to 100 degs. C, and show differ- 

 ences of o'oi degs. C. Mr. Chaney also showed an 

 exceedingly delicate balance, which will indicate the 

 one-hundred-thousandth part of a grain. Mr. Turner 

 exhibited an apparatus for determining the hardness of" 

 metals or other substances. A polished surface of the 

 metal to be tested is brought underneath a weighted 

 diamond, which is moved in such a manner as to produce 

 a visible line on the smooth surface. The weight in 

 grammes necessary to produce a standard visible scratch 

 is taken as a measure of the hardness of the material. 



Mr. Shelford Bidwell showed his apparatus for mea- 

 suring the changes produced by magnetisation in the 

 dimensions of rods and rings of iron and other metals ;, 

 this instrument being capable of measuring changes of 

 length to a twenty-five-millionth of an inch. An iron 

 rod when magnetised becomes at first slightly lengthened;, 

 but if the magnetising force is sufficiently increased it 

 again contracts, and ultimately becomes shorter than 

 when unmagnetised. Cobalt and nickel both contract, 

 while bismuth becomes slightly elongated. 



Mr. Norman Locker conducted same experiments illus- 

 trating low temperature spectra in connection with the 

 spectra of meteorites, and showed the spectra of magne- 

 sium, lead, iron, barium, manganese, etc., at the tempe- 

 rature of the oxy-coal gas flame, and also the conditions of 

 the disappearance of the C and F lines from the spectrum 

 of hydrogen. 



Mr. J. M. Richards exhibited Robertson's Writing 

 Telegraph, which transcribes with a pen on a strip of 

 paper at both ends of the line the actual writing of the 

 transmitter, so that both the sender and receiver have a 

 written copy of the message sent. Mr. E. S. Bruce 

 showed his electrical translucent captive balloon for 

 flashing signals by night, which can be used for signalling 

 to long distances, and in places where ordinary signalling 

 would be impracticable. 



The Woodhouse and Rawson Electric Supply Com- 

 pany exhibited Mr. Vernon Harcourt's new Pentane 

 Standard Lamp ; the Holophotometer, for measuring the 

 intensity of a light all round ; and a new carbon Micro- 

 phone Button for Blake's transmitters. The Schwans- 

 schieff Electric Light and Power Company, and the 

 Edison and Swan Electric Light Company both sent 

 specimens of their electric safety lamps for miners. 



Prof. Flower showed a skeleton of an Akka, which, 

 has been sent by Dr. Emin Pasha for the British 

 Museum. The Akkas, a negro tribe of Central Africa, 

 are the smallest known race of men. The height of the 

 skeleton is exactly four feet. 



Among the other exhibits may be mentioned : Speci- 

 mens of gold and bismuth, showing the effect of small 

 quantities of impurity on the fracture of the metal, by 

 Prof. Roberts-Austen ; apparatus for the isolation of the- 

 element fluorine, by Prof. T. E. Thorpe ; a Coulomb 

 meter, by Prof G. Forbes ; the new iridio-platinum 



