90 



NATURE 



[May 27, 1697 



reflection, comes. This difficulty is also explained on this 

 "principle," for it "accounts for how light itself is generated, 

 for the forces that generate light . . . are everywhere at work, 

 though the result may not be immediately apparent to our 

 senses." As this " principle " seems to be capable of enlighten- 

 ing astronomical science on so many points, we think we have 

 mentioned enough of them for the reader to imagine the rest. 



The Nebula ok Orion. — Two publications of the observa- 

 tions of the nebula of Orion have recently come to hand, one 

 relating to eye observations, and the other restricted to photo- 

 graphic work. The former of these forms part of the publications 

 of the " Leander McConnick Observatory of the University of 

 Virginia " (vol. i. part 7), and consists of the eye observations 

 made by the Director, Mr. Ormond Stone. A minute com- 

 parison of the results obtained by this survey with those given in 

 the second publication should no doubt prove of great interest. 

 This latter work we owe to Ur. Scheiner ; it forms the second 

 part of the eleventh volume of the " Publicationen des Astro- 

 physikalischen Observatoriums zu Potsdam." In this Dr. 

 Scheiner has investigated the details of this nebula as registered 

 by several photographs, and he had also, with the intention of 

 tracing some relationship between the nebula and the stars in 

 and around it, completed a rigorous measurement of the position 

 of the stars on the photographic plates. The main result of the 

 investigation shows that undoubtedly there is a relationship 

 between the nebula and the neighbouring stars. This result is 

 satisfactory in that it is just what we should expect on the 

 nieteoritic hypothesis, and further corroborates Mr. Isaac Roberts's 

 recent work, which alsp indicated a close connection between 

 stars and nebulae. 



The Parallax ok 61' Cygni.— Mr. Herman S. Davis con- 

 tributes to the Astronomical Journal, No. 402, the results of his 

 investigation of the parallax of 61^ Cygni. In this work he has 

 employed the nineteen negatives of this star taken, between the 

 years 1871-74, by Mr. Rutherfurd. The methods of reduction 

 by differences of distance of two stars, having approximately 

 equal distances, and differing about 180° in position-angle, 

 are here the same as were employed for the parallax of yu, 

 Q and tj Cassiopeiae in previous investigations. In addition to 

 measures of distance, those of angle have here been employed. 

 Taking the means of the values given in the Astronomical 

 lournal, that for measurement of distance is + o" 3999 

 + o"o230, and for measurement of position-angle 4- o "3326 

 + o"oi89. The resulting value for the mean relative parallax 

 of this star is therefore -t- o"'36o + o"oi46. Mr. Davis adds 

 that a complete discussion of the measure of 61^ Cygni will soon 

 be published as Contribution No. 13 from the Observatory of 

 Columbia College. 



THE ROYAL SOCIETY CONVERSAZIONE. 

 "T^HE first of the two conversazioni held annually at the 

 Royal Society took place on Wednesday, May 19. The 

 following is a list of the exhibits : — 



Illustrations of the DansacChassagne process of producing 

 photographs in colour : Sir H. Trueman Wood. 



Apparatus for ascertaining duration of explosion, pressure 

 developed, and rate of cooling of products of combustion : Sir 

 A. Noble, K.C.B., F. R.S. The recording instrument consists 

 of a rotating drum on which two pencils mark (i) seconds, (2) 

 the pressure in tons per square inch indicated by a specially 

 designed manometer ; the pressure pencil traces out a curve, 

 from which can be deduced the approximate time of explosion, 

 the pressure reached, and the rate at which the gases cool ; a 

 second instrument is attached, on which the pressures and seconds 

 are indicated by small electro-magnets. 



Stress effects produced by convective electric discharges : Mr. 

 J. W. Swan, F.R.S. 



Apparatus for the comparison of thermometers : Mr. W. 

 Watson. 



A powerful electrical influence machine : Mr. J. W^imshurst. 

 The machine has 24 discs, each 3 feet in diameter ; they are so 

 arranged as to furnish three poles, one of which may be 

 negatively charged, the other two poles positively charged, or 

 at pleasure the reverse order may be followed ; by this arrange- 

 ment two separate streams of discharge may be in use at the 

 same moment. 



NO. 14.^9, VOL. 56] 



(l) Model of a Hertz wave transmission ; (2) two kinematic 

 models : Prof. Silvanus P. Thompson, F.R.S. 



Graphic representation of the Rothamsted observations on 

 the continuous growth of wheat : Dr. H. E. Armstrong, 

 F.R.S. 



Certain bones of the ancient Naquada race, exhibiting 

 characters of morphological or pathological interest : Mr. E. 

 Warren. 



Restored skeleton of yEpyprnis Hildebrandi (Burckhardt) 

 from Madagascar. The skeleton exhibited is, the first and 

 almost complete skeleton of Aipyornis Hildebrandi hitherto 

 obtained from Madagascar. Nesopilhectis Koberti (Forsyth- 

 Major), a fossil monkey of an entirely new genus, and other 

 objects : Dr. C. I. Forsyth-Major. (The collection was made 

 by means of grants from the lund administered by the Royal 

 Society.) 



Glacial phenomena of Cambrian or Pre-Cambrian age, 

 from the Varanger Fjord, Norwegian Lapland : Mr. Aubrey 

 Strahan. 



Photographs of the moon taken with the new Thompson 

 26 in. photographic telescope, at the Royal Observatory, Green- 

 wich : the Astronomer Royal. 



Photographic Atlas of the Moon, published by the Observatory 

 of Paris; executed by MM. Loewy and Puiseux : the Library 

 of the Royal Society. 



(i) Photographs illustrating enhanced lines in the spectra of 

 the chemical elements, and the importance of such lines in the 

 spectra of the hotter stars. (2) Solar photographs, taken at 

 Dehra Dun, India, showing a kite and a locust projected on 

 the sun's disc. Forwarded by Mr. J. Eccles. (3) Photo- 

 graphs illustrating the spectroscopic results obtained by the 

 Eclipse Expedition to Novaya Zemlya, August 1896. (4) 

 Photographs illustrating preparations and arrangements for the 

 observation of the total eclipse of the sun August 1896, at Kio 

 Island, Varanger Fjord, Norway : Mr. J. Norman Lockyer, 

 C.B.,F.R.S. 



Experiments with kathode and X-rays : Mr. A. A. C. 

 Swinton. 



A selection of dried plants from Tibet, collected by Captain 

 Deasy and Mr. Arnold Pike, Captain Wellby and Lieutenant 

 Malcolm : the Director, Royal Gardens, Kew. 



Photographs illustrating the micro-structure of alloys : Mr. 

 J. E. Stead. 



Some photographs of optical projections in space : Mr. Eric 

 Stuart Bruce. 



Apparatus showing the phase change of light reflected at a 

 glass-silver surface : Mr. E. Edser and Mr. H. Stansfield. The 

 apparatus exhibited is a modification of Michelson's differential 

 refractometer, the interfering rays being reflected at the back 

 surfaces of the end mirrors. On these surfaces are deposited 

 silver films, one being wedge-shaped, with a horizontal streak 

 rubbed off, and the other uniform. Where vertical bands cross 

 from the glass-air to the glass-silver surface a lateral displace- 

 ment is produced, which varies from zero at the thin end of the 

 wedge to 5 of a band at the thick end. The direction of the 

 displacement indicates a retardation. 



Apparatus for micro-photography : Prof. Roberts- Austen, 

 C.B., F.R.S. A microscope and camera is arranged for ob- 

 taining photographs of metals and alloys under high magnifica- 

 tion. The illustrations show the mode of existence of carbon in 

 steel, and include the diamond form of carbon. The magnifica- 

 tions vary from 500 to 1000 diameters. 



Living specimens of Proteus anguinus, Laurenti : Mr. E. J. 

 Bles. 



A collection of British Medusas : Mr. E. T. Browne. 

 • ( I ) Experiments with highly-dilatable and nearly non-dilatable 

 nickel steel ; (2) diagrams of expansion ; (3) compensated 

 pendulum made of nickel steel : M. C. E. Guillaume, Bureau 

 International des Poids et Mesures. 



(I) Superficial colour changes of a silver-zinc alloy ; (2) X-ray 

 photographs of sodium-gold alloys : Mr. C. T. Heycock, F. R. S. , 

 and Mr. F. H. Neville. 



(i) Improved hatchet planimeter ; (2) the cyclesograph, an 

 instrument for describing arcs of circles of large radius : Mr. 

 E. K. Scott. 



The diffraction kaleidoscope : Mr. C. P. Butler. 

 A mid-water tow-net : Dr. G. H. Fowler. 

 Rotating discs, showing subjective colour phenomena : Mr. 

 Shelford Bidwell, F.R.S. 



Demonstration of Zeeman's discovery of the broadening of 



