26o 



NATURE 



[December 21, 191 1 



'1 



11 



were mingled with the nitrogen in the globe. Further 

 experiments on the effect of pressure were made, and the 

 causes of the phenomena briefly discussed. 



Thirty-thrcf! firms exhibited their latest forms of physical 

 apparatus. Only a few of the various new formt of instru- 

 ments can be mentioned. A new galvanometer of the 

 moving-magnet tvpc was shown by the Cambridge Scientific 

 Instrument Co., "who claim for it a sensitiveness forty 

 times that of their Broca type. The magnet system con- 

 sists of two groups of very small magnets arranged on a 

 fine glass stem, which is suspended from a quartz fibre. 

 The coils are arranged in pairs similar to a Thomson 

 galvanometer, and are designed to secure the maximum 

 effect for a given resistance of copper by winding with 

 different sizes of wire, beginning with the smallest size, and 

 winding each layer so that it lies within the surface of 

 which the polar equation is r' = d'sin«, where r is the 

 length of radius, making an angle B with the axis of the 

 coil. The company displayed several other exhibits of their 

 instruments for advanced work, including a Duddell oscillo- 

 graph outfit for a 50,000-volt circuit. A new design of 

 extensometer was shown by W. G. Pye and Co., for use 

 in conjunction with a testing machine on bars and thick 

 specimens. It was composed of the Ewing extensometer 

 with the microscope replaced by an optical lever, and was 

 designed to measure extensions of 1/100,000 of an inch. 

 Several new designs of students' apparatus and a Kohl- 

 rausch bridge of new form were included among their other 

 exhibits. A new vibragraph was shown by Siemens 

 Brothers and Co., Ltd., consisting of a mercury reservoir 

 with a floating mirror, by means of which a beam of light 

 from a small glow-lamp is reflected on to a ground glass 

 screen or photographic plate. The mercury ripples set up 

 by the vibration of the body on which the reservoir is 

 placed give an angular movement to the mirror, which thus 

 produces on the plate or screen a clearly defined diagram 

 of the vibration. The same company also showed a 

 demonstration wireless-telegraphy set on the singing-spark 

 system, and a number of frequency indicators. 



New projection apparatus and a new level for very 

 accurate surveying was shown by Carl Zeiss, Ltd. Photo- 

 micrographic apparatus, and an ultra-condenser for render- 

 ing an ordinary microscope suitable for ultra-microscopic 

 observations were among the exhibits of Messrs. E. Leitz. 

 Their latest pattern of high-vacuum oil pump was shown by 

 A. C. Cossor, Ltd. The piston of the high-vacuum cylinder 

 is actuated from outside by an electro-magnet, which is 

 caused to move up and down, thus avoiding the use of a 

 piston rod and possible leak at the stuffing boxes. The 

 Foster Instrument Co. exhibited a simple strain-meter for 

 observation of strains in any part of a structure, such as a 

 girder of a bridge or frame of a ship. 



Various types of switchboard instruments were shown by 

 Nalder Bros., R. W. Paul, and the Weston Instrument 

 Co. .Among the exhibits of the last-named was a new line 

 of alternating-current dynamometers, including wattmeters, 

 frequency meters, and synchroscopes. R. W. Paul also 

 exhibited a new and inexpensive form of potentiometer, 

 various inductionless resistances, and a number of thermo- 

 couple pyrometers and temperature indicators. Messrs. 

 Gambrell lBros. exhibited a new potentiometer for thermo- 

 electric work, and instruments of various kinds for students' 

 use. The Silica Syndicate displayed some wonderful 

 examples of their wares. Electric furnaces were shown by 

 J. J. GriflRn and Sons, Ltd., together with quartz glass 

 mercury thermometers for temperatures up to 750° C. 



Demonstrations of Dr. Leonard Hill's colour vision 

 apparatus were made at the stand of Messrs. Newton and 

 Co. The degree of sensitivity of the eye for colours is 

 ascertained by means of two identical spectra projected by 

 an optical lantern from one and the same prism, and 

 provided with separate adjustable screens for matching. 

 Electrical apparatus for medical purposes was shown by the 

 Sanitas Electrical Co., and X-ray apparatus by H. W. Cox 

 and Co. E. Ravmond-Barker's two-tone transmitter, 

 exhibited by the Tndia-Rubber. Gutta-Percha and Telegraph 

 Works Co., Ltd., and F. Harrison Glew's radio-active 

 preparations, are two of many other interesting exhibits, of 

 which our space does not permit us to give more detailed 

 account. 



NO. 2199, VOL. 88] 



THE ASTRONOMICAL AND ASTROPHYSICAI 

 SOCIETY OF AMERICA.' 



FOR the first time in its history the Astronomical and 

 Astrophysical Society of .\merica this year held it>. 

 annual meeting outside the Unitc-d States, and it speaks 

 well for the progress of the comparatively young Dominion 

 Observatory that the locale was Ottawa. This feeling was 

 made the subject of a special resolution, in which a very 

 favourabU: opinion as to the character of the work done in 

 every department was united with a recommendation that a 

 more |>owerful telescope may soon be provided (or use in 

 the important radial-velocity work now being executed at 

 this observatory. 



Prof. E. C. Pickering was elected president, Profs. Frost 

 and Campbell vice-presidents, and Mr. Plaskett, of the 

 Dominion Observatory, was elected a councillor. A great 

 numb<>r of papers were read during the five sessions held 

 on August 23, 24, and 25, and the general feeling wa» 

 that in every respect this twelfth annual meeting was 

 eminently successful. We briefly note a few of the paper* 



here. . . . . ^. 



Prof. Pickering read a paper m connection with the 

 symposium on photographic astrometry, showing how th- 

 first point of Aries might be determined photographically. 



Miss Cannon announced that the spectra of 762 double 

 stars of magnitude 75 and brighter had been especially 

 examined on the Harvard photographs, and also explamed 

 that an examination of some 131 stellar spectrograms taken 

 with slit spectrographs was being made, in order to see 

 whether the same system of classification can be applied 

 to such spectra as was applied to the store of objective- 

 prism spectra at Harvard. It is difficult to see why the 

 classification should differ, although more details may be 

 seen and so give finer divisions ; but we hope that this work 

 will not lead to further complications in the already com- 

 plicated nomenclature of the Harvard system. 



Mr. Parkhurst examined a number of stars given in a 

 list by Prof Pickering purporting to comprise " Fourth 

 Tvpe Stars not Red " (class R), and extended to include 

 some ordinary red stars (class N). By his photo-visual 

 magnitude method he finds that with one exception the stars 

 are all redder than Aldebaran, and therefore no sharp line 

 should be drawn between classes R and N. 



Mr. Harper, of the Dominion Observatory, read a paper 

 on the orbits of the spectroscopic components of d Bootis, 

 and Mr. Joel Stebbins explained how the selenium photo- 

 meter had revealed a range of 02 mag. in the brightness 

 of Betelgeuse during 1910-11, and had shown 5 Orionis 

 (range 010 mag.) and jB Aurigae (range <o-io mag.) to be 

 eclipsing variables. Polaris too, as shown by Mr. E. S. 

 King's examination of Harvard plates, has a variability of 

 0108 mag. 



Some results of a studv of visual binary stars by Dr 

 H. N. Russell suggest that the whiter stars are very much 

 brighter, for equal masses, than the redder stars, and that 

 the stars of a given type are of equal mass and of equal 

 luminositv. Examining some 349 stars of various spectra! 

 types, he' finds that about half of them are very much 

 brighter in proportion to their mass than the others. This 

 half includes all the stars of the B type, among those 

 examined, and some of every other type, and these stars 

 may probably be classed as the " giant " stars of Hertz- 

 spriing's division, a class in which the systems are more 

 or less uniformly of about ten times the sun's mass; no 

 such uniformity is found in the average masses of thi 

 " dwarf " stars', which appear, in the average, to beconv; 

 less massive as they become redder. A pair of " giant ' 

 stars would emit some 150 to 250 times the light emitted 

 by the sun — the higher value being for class B stars — 

 whereas a pair of " dwarfs " if of the A class might give 

 30 times, and if of the Kj, or M, class, one-hundredth, the 

 light emitted bv the sun. 



The 6-inch transit circle of the U.S. Naval Obser\'atorv 

 has attacked its programme of fundamental stars, both th' 

 old ones and those for the International Chart, and it- 

 behaviour was described by Prof. Littell. 



Dr. Humphrey's p.ipers showed (i) that the various zones 

 of the earth are not equally efficient radiators ; both the 

 1 Condensed from the secretao's report in Scietice, N S., vol. xxxiv.. 

 No. 877, pp. 520-536. 



