352 



NA TURE 



[August io, 1905 



questions and problems, and is likely to continue to be 

 a popular manual on the outlines of inorganic chemistry 

 and chemical philosophy. 



Messrs. M.\cmill.\n and Co., Ltd., have issued a new 

 and revised edition of stage vi. of- Jlr. Vincent T. 

 Murch^'s " Object Lessons in Elementary Science," the 

 price of which is 2.?. 



.■\ FIFTH edition of Mr. W. W. Fisher's " Class Book 

 of Elementary Chemistry " has been issued by the 

 Clarendon Press, Oxford. The text has been entirely re- 

 vised, and numerous additions have been made. .Several 

 chapters on organic chemistry, intended to serve as an 

 introduction to this division of the subject, have been 

 included in the new edition, which is now in line with 

 the present state of knowledge of the subjects dealt with 

 in the volume. 



OVR kSTRONOmCkl^ COLUMN. 

 Jupiter's Sixth .\xd Seventh S.itellites. — A telegram 

 from Prof. Pickering to the Kiel Centralstelle announces 

 that Dr. Albrecht has observed the recently discovered 

 sixth satellite of Jupiter with the Crossley reflector of the 

 Lick Observatory. The times of observation and the 

 determined positions were as follows : — 



G. M.T. Position angle Distance 



1905 July 25-95 ... 55-0 ••• 25"i 



2697 ... 527 ... 24-3 



27-93 ■ ■■ 507 ••• 23'6 



(Circular No. 77. Kiel Centralstelle). 

 In Bulletin No. S2 of the Lick Observatory Dr. Frank 

 E. Ross publishes the following set of elements for the 

 orbit of Jupiter's seventh satellite, which he has coinputed 

 from the observations made by Prof. Perrine on January 3, 

 February 8, and March 6 : — 



Ecliptic Elements. 



Mean Jovicentric Longitude at Epoch ... 33355 



Longitude of Perijove ... 336'65 I 



,, Node 237-23 



Inclination to Ecliptic 31-0 | 



,, Jupiter's Orbit ... ... 32-0 



Longitude of Node on Jupiter's Orbit ... 23S 6 



1905 

 Jan. CO 

 G.M.T. 



Elcwcnts referred Io Earth's Equator. 

 Mean Jovicentric Right Ascension... ... 32S iS 



Right Ascension of Perijove ... ... 331-28 



,, ,, Node ... 281-13 I 



Inclination to Equator ... ... ... 26-2 



Mean Daily Motion = i°-358 

 log = 8-9004 



n = 5'2'-54 (for log A = o-7l624) 

 c = o -0246 

 P = 265-0 days 

 Distance at maximum elongation = 70'. 



Calculating from these elements the positions at the 

 times of Prof. Perrine's observations, it was found that 

 the residuals were satisfactorily small, but for five inter- 

 mediate dates, on which observations were secured, they 

 proved to be larger than were expected. Dr. Ross accepts 

 this result as evidence of the large periodic perturbations, 

 chiefly solar, to which the satellite is subjected. The 

 above elements indicate that this satellite revolves about 

 Jupiter in a direct orbit, for although a retrograde orbit 

 was computed and found to fit the three primary observ- 

 ations, it did not agree wnth the positions obtained from 

 the intermediate observations. 



An ephemeris, covering the period July i to 

 November 13, from which the following positions are 

 taken, accompanies Dr. Ross's paper: — 



Aug 



On October 4 the distance will still be 59', but after 

 that date it will slowly decrease, until on November 13 it 

 will be only 18'. 



.According to a note communicated by Prof. Perrine to 

 the Astronomical Society of the Pacific, and reproduced in 

 No. 4035 of the Astroiwmische Nacinichtoi, Dr. Ross has 

 also computed the orbit of Jupiter's sixth satellite. This 

 satellite, like the se\-enth, moves in a direct orbit, its 

 period being 242 days. The eccentricity of the orbit is 

 large, amounting to o-i6, and the inclination to the plane 

 of Jupiter's equator is about 30°. The mean distance of 

 the satellite from Jupiter is about seven million miles. 

 Thus the periods, and therefore the distances from Jupiter, 

 of the sixth and seventh satellites are nearly alike, their 

 orbits mutually interlocking. Otherwise the two orbits 

 are dissimilar. 



The Forxhtion of the New North Pol.ar C.ip on 

 Mars. — According to Mr. Lowell's observations, as re- 

 corded in No. 22 of the Lowell Observatory Bulletins, the 

 first frost of this year in the Arctic regions of Mars 

 occurred on May 19. The region wherein the phenomena 

 were observed had been under daily scrutiny since coming 

 into view on May 11, but no new feature had been dis- 

 covered. However, on May 19 an enormous, unmistak- 

 ablv white patch was seen which extended from the 

 western edge of the old cap to a point on the terminator 

 about one and a half times the old cap's diameter away, 

 and reached down to latitude +63°. 'fhe deposit was so 

 thin on its northern edge that the band girdling the old 

 cap could be plainlv seen show'ing through it, but on 

 May 20 a bright nucleus formed on the southern edge of 

 the frost-bound area. 



The date of the first observation corresponds to 

 August 20 in our calendar, and is 126 days after the 

 summer solstice in the northern hemisphere of Mars. In 

 1903 the first frost effects were observed on Mars about 

 128 days after the summer solstice; thus the recent 

 observation strongly confirms those made in 1003. 



LIQUID AIR—PR(WUCTIOX .l.\D 

 APPLICATIOXS.' 

 T N the former of these papers the author details experi- 

 ments showing the trustworthiness of a German silver 

 platinum couple to measure temperatures in the neigh- 

 bourhood of those of liquid air and liquid and solid 

 hydrogen. The electric resistance of metals is an unsafe 

 guide at very low temperatures, and the manipulation of 

 gas thermometers involves much time and care. A thermo- 

 electric junction would be much more convenient if trust- 

 worthy. That it is trustworthy the experiments go to 

 show, but onh' within limits. If the constants of the 

 formula for interpreting the observations be determined 

 at temperatures between qoi" and 1235° abs., the formula 

 will then give the temperature of solid hydrogen at low 

 pressure as i5°-27 abs., whereas if the constants be de- 

 duced from experiments at a lower temperature, 20^° to 

 775°, the interpretation formula then makes the tempera- 

 ture of solid hydrogen at low pressure i|° low-er, i.e. 

 i3°-5 abs., which the author considers more correct. 

 Bearing in mind that at this very low temperature a 

 difference of 15° is equivalent to a difference of 37° at 

 the ordinary temperature, we see that the method has no 

 confirmatory value, and can itself be trusted only over 

 the range for which it has been verified bv the careful 

 use of gas thermometers. If, therefore, helium be pro- 

 cured in sufficient quantity for liquefaction or solidification, 

 its lower temperatures, possiblv within 5° of the absolute 

 zero, will have to be ascertained by the low-pressure 

 helium thermometer. For ranges of temperature over 

 which its indications can be verified, the thermoelectric 

 junction thermometer will have a useful sphere of work in 

 saving the inconvenience of emploving gas thermometers. 

 .•Vmong important cautions given by the author is a warn- 

 ing that junctions made with soft solder are affected by 

 the low temperature. The junctions should be made with 

 hard silver solder, and the indications at the temperature 



1 "On th'j Tliermo.-lectric Junctijn a-; a Means of Detfrmining the 

 Lowest Temperatures, and 1 n Liquid Hydrog-n and .Air Calorimeters." 

 Papers by Sir James Dewar. read before t..e Royal Socxl> , June 8, 1905. 



