176 



NA TURE 



[August 4, 192. 



been needed for some time has been completed and is 

 now in use, but the work in the physics building is still 

 congested. 



An opportunity has been afforded us to examine 

 and test the Hatchctt planimeter and the pantograph 

 designed and manufactured by W. H. Harling, 

 117 Moorgate, E.G. 2. The planimeter is very simple 

 and compact in form : after a little practice it can be 

 made to give results of considerable accuracy. The 

 writer has tested it on variously shaped areas of 

 different sizes, with good results. The pantograph is 

 a more complicated instrument, designed on the 

 principle of simple parallelograms, and can be set to 

 sixteen different ratios. Geometrically, the instru- 

 ment seems to be quite satisfactory. In use, however, 

 one or two faults can be detected. First, there is not 

 enough pressure on the pencil point to produce a 

 useful drawing. Second, the pencil is not steady, 

 there being insufficient constraint for keeping it per- 

 pendicular to the plane of the instrument. If these 



faults are remedied, the pantograph should prove very 

 useful. Both instruments ;<red at moderate 



prices. 



The Milroy Lectures on " Canned Foods in relation 

 to Health," which were delivered a short time ago 

 by Dr. W. G. Savage, are to be published in the 

 autumn, in the Cambridge Public Health Series, by 

 the Cambridge University Press. 



Messrs. J. and A. Churchill are about to publish 

 " Clouds and Smokes : the properties of disperse 

 systems in Gases," by Dr. W. E. Gibbs, in which will 

 be described the various ways in which disperse 

 systems in gases can be formed ; their mechanical, 

 thermal, optical, and electrical properties, and the con- 

 ditions which determine their stability are discussed. 

 This information is then applied to the practical 

 problems of meteorology, fume condensation, gas 

 filtration, the manufacture of substances in a finely 

 powdered condition, and the use of smoke in warfare. 



Our Astronomical Column. 



The Great Perseid Meteor Shower. — Mr. W. F. 

 Denning writes : " The maximum of the Perseids 

 occurred in 1921 on the morning of August 12, and 

 the earth may be expected to be in the same position 

 of its oiT^it in the early afternoon of August 12 next. 

 There may therefore be no very rich shower, though 

 one may possibly recur in Japan and in the East. 



Our acquaintance with the distribution of the 

 Perseids is, however, by no means perfect, and it is 

 fairly certain that a fairly good display will be 

 observed in England this year if the weather allows 

 suitable observations to be made. The moon being 

 new at the time of the maximum will be a favouring 

 feature. 



Observations should be made on the early morning 

 of August 12 and during the night following that date. 

 The hourly number of meteors should be counted, 

 and the apparent paths among the stars of the larger 

 ones should be accurately recorded so that their 

 real paths may be computed. 



It will be interesting to note if there are any strong 

 displays of the minor radiants of this period, such as 

 the Cepheids, Cygnids, Lyrids, or Arietids." 



Observations of Jupiter. — L'Astronomie for July 

 contains three drawings of Jupiter on April 24 and 

 May I by M. Pierre Feurtey, using an equatorial of 

 o-ig metre aperture screened down to 0-14 metre. 

 The Red Spot, the tint of which is described as 

 saunion gris, seems to have revived since last year, 

 as it is shown quite strongly marked in the drawing 

 of May I, with two lighter patches in its interior, 

 and the surrounding bays, both north and south, 

 very dark. A row of six round white piarkings 

 follows the spot, slightly to the north of it. 



Several narrow dark bands cross the light equatorial 

 zone obliquely. 



Parallaxes of Fifty-seven Stars. — The Memoirs 

 of the National Academy of Sciences (Washington), 

 vol. xix., contains the results of the determination 

 of the parallaxes of fifty-seven stars made by Mildred 

 Booth and Frank Schlesinger. In twenty - two 

 of these no previous determinations of parallax 

 have been made. The authors point out that, 

 without the co-operation of several institutions, a 

 long interval would have elapsed before these results 

 could have been made available. Thus the photo- 

 graphic plates were secured with the Thaw photo- 



NO. 2805, VOL. I 12] 



graphic refractor of the Allegheny Observatory : 

 the measures and reductions were completed at the 

 Yale Observatory under a grant from the National 

 Research Council (Division of Physical Sciences) to 

 the committee on Stellar Parallaxes of the American 

 Astronomical Society. The measuring machine was 

 purchased several years ago with a grant from the 

 Draper Fund of the National Academy of Sciences. 

 The measurements and computations were carried 

 out by Miss Booth, the methods employed having 

 been previously published. The aA'erage number of 

 comparison stars used was 3-8, and the average 

 number of plates for each region was 15. It is 

 interesting to note that a great many of the stars 

 in the list are double ; thus nearly every object is 

 one of more than average difficulty, the stars having 

 in fact been selected on that acc6unt from a long 

 list awaiting attention at Allegheny. A summary 

 of the parallaxes is given in a table showing the 

 visual magnitude and spectrum type, total proper 

 motion, relative parallax and probable error, and 

 finally, the probable error for one good plate. 



Spectroscopic Binaries. — The Dominion Astro- 

 physical Observatory, Victoria, is determining orbits 

 for a number of these binaries. The chief interest 

 in this research is the material for determining the 

 average mass of stars of each spectral type. The 

 masses of individual stars are indeterminable owing 

 to the uncertainty of the inclination, but in study- 

 ing a large number of binaries we may assume that 

 the inclinations follow the law' of random distribution. 

 The elements of the following three stars have lately 

 been determined : 



BD 44° 3639 

 Boss 4870 

 4> Aquilae 



Spectral Tj-pe. Period. 



Oe 5 48-608 days 

 B 2 1-0309 „ 



A 2 33204 „ 



?tlass in terms of 

 sun's mass. 



0-374 



0-00019 



0-0192 



The first is of special importance, since few masses 

 of this type are known. One spectrum only is 

 visible in each of these cases, so the companion is 

 likely to have smaller mass. In the Oe 5 spectrum, 

 the sharp H and K lines do not share in the oscilla- 

 tions and give a velocity of - 11-3 km. /sec, as com- 

 pared with - 5-8 km. /sec. for the centre of gravity of 

 the system. 



