33 



SCIENCE. 



JUPITER. 



By Prof. G. W. Hough, Director Dearborn Observatory. 



During the present opposition of Jupiter, the disc ex- 

 hibits a variety of phenomena of interest to the practical 

 astronomer. 



Although this planet has received a good deal of atten- 

 tion during the past century, yet, but few new facts have 

 been added, with regard to its physical aspect, since the 

 time of Sir Wm. Herschel. 



It appears to be the generally accepted idea that its 

 surface is subject to sudden and extraordinary changes, 

 sometimes accomplished in a few days or even a few 

 hours. New belts are alleged to have been formed or to 

 have disappeared in the course of an hour or two. 



We believe conclusions of this kind have been too 

 hastily drawn from the obstructions. 



Owing to the rapid rotation of Jupiter, the various spots 

 and markings follow each other so closely that one 

 might readily imagine that what he saw was subject to 

 change under his eye. 



The great red spot, which has been an object of so 

 much interest since 1879, becomes visible, in the Chicago 

 telescope, at 2h. 25m. from the meridian of the planet, 

 when its length is about one second of arc. As the rota- 

 tion carries it further on the disc, it gradually increases 

 in size, until, when on the meridian, it subtends an angle 

 at opposition, of 15 seconds. The smaller spots and 

 markings, of course, become most conspicuous when 

 near the meridian of the disc. 



The visibility of objects depend, very much, also, 

 on the condition of the seeing. Sometimes the smaller 

 spots are invisible for weeks, simply because the 

 seeing is not good enough with limited optical power, 

 and not because there has been any radical change on 

 the surface of the planet. Its distance from the earth is 

 another important element in modifying the appearance 

 of phenomena. After conjunction, the great Equator. al 

 Belt and Red Spot are first seen and, as the earth ap- 

 proaches nearer, other markings gradually appear, until 

 the time of opposition, the greatest variety of phenomena 

 is noticeable. 



From September, 1879, when micometer measurements 

 were first begun, with the Chicago Refractor, on the 

 markings of the disc, considerable change has taken 

 place in its appearance at different times. But all changes, 

 whether due to the distance of the planet from the earth, 

 variable seeing, or other causes, have been slow and 

 gradual. 



The most noticeable change has taken place in belt 

 No. 3 situated 6" north of the equator. This belt, which 

 was not conspicuous in 1879, gradually increased in 

 width and distinctness in 1880, until at the present time 

 its width is about 2". 5 ot arc, and of the same color as the 

 equatorial belt, viz ; reddish brown. 



The equatotial region situated between the two out- 

 lines of the equatorial belt has been subject to consider- 

 able change, but the margins of the belt have not sen- 

 sibly varied in width or latitude during the past three 

 oppositions. 



The great red spot, a conspicuous object even in a small 

 telescope, is alleged to have materially changed in length 

 during 1879, ar >d again in 1880, but numerous micrometer 

 measurements do not confirm this statement. 



The following are the mean results, reduced to the 

 mean distance. 



Length. No. of lireadth. No. of Latitude. No. of 



Obs. . Obs. . Obs. 



1879 12.25 9 3.46 8 —6-95 8 



1880 H-55 20 3-54 10 — 7.14 12 



1881 11.50 8 3.49 3 — 7.41 7 



These numbers indicate a small possible displacement 

 of the center in latitude, but it would be premature to 

 assume such to be the case. 



The color of the spot is reddish-brown ; however, when 



the seeing is unusually good, it appears almost a light 

 pink. 



The oval-shaped white spots, a number of which were 

 observed in 1880, are quite numerous at the present time. 

 They are about one second of arc in length and are gen- 

 erally difficult objects to observe. 



The following spots have been seen on belt No. 6. 

 Latitude 9". 5 to 12". 6. They pass the meridian of 

 Jupiter after the great red-spot as follows: 



h. h. h. h. h. h. h. h. 

 + 2.8 + 3.0 + 3.3 + 4.0 + 4-7 + 5-2 + 5-5 +5-8 



There are also two white spots — more easily seen — 

 near the great red spot in latitude 9". 63 and longitude 

 oh. 36m. and +oh. 24m. 



The two white spots situated in latitude 3". o south 

 of the equator, which were observed in 1879 and >88o, 

 were first seen this year on July 22. They appear to 

 make a complete revolution around the planet in about 

 forty-five days, corresponding to a rotation period of 9h. 

 50m. 9 sec. 



These spots, which are both occasionally seen at the 

 same time, appear to be fixed relatively to each other. 



The difference of longitude was measured with the 

 micrometer as follows : 

 1880. 

 July 24, +23.501. 

 Nov. 8, + 22.6m. 



1881. 

 July 22, +27.501. 

 Nov. 26.. +27. 5m. 

 Dec. 10, +23.om. 



The fact that they have maintained for a year and a 

 half the same relative position, and at the same time 

 apparently drifted with a velocity of over 260 miles per 

 hour, would seem to disprove the old theory that they 

 are clouds floating in the atmosphere of the planet. 



From observations made during the present opposi- 

 tion, it is probable that all the matter between the two 

 margins of the equatorial belt, whether in the form of 

 white spots or dark ones, moves with the same velocity, 

 viz. : a period of 9b). 50m. 9 sec. And it is possible that 

 the belt itself partakes of this motion. 



The rotation period of the planet, deduced from our 

 observations on the red spot, made in 1879 and 1880, 

 was 9h. 55m., 33.2 sec. + 0.09 sec. y/~in which / is the 

 number of days after Sept. 25, 1879. The observations 

 during 1880 showing that the spot was retrograding 

 with an accelerated velocity. 



This formulas is found to be essentially correct for 

 the present opposition. 



The "mean" period for Dec. 14, 1881, comprising 

 an interval of 811 days, being 9h. 55m., 35.80 sec. from 

 observation and 9I1. 55m. 35.76 sec. from the formulas 



Assuming the rotation period as above, the centre of 

 the spot has retr6graded more than fifty degrees since 

 Sept. 1879, not uniformly, but with an accelerated velocity. 

 It seems difficult to account for this fact on any known 

 hypothesis. 



IMPROVEMENTS OF PLANTE AND FAURE'S 

 STORAGE BATTERY. 



In a previous number of "Science" No. 57, July 30th, 

 1881, we gave excellent directions for making Plante and 

 Faure's storage batteries. — In a recent paper before the 

 " Society of Arts, of London, Professor S. P. Thompson 

 states that almost any oxide or hydrate of lead will answer 

 for use in the Faure battery— Litharge will answer if suffi- 

 ciently finely divided for being painted on. Litharge mixed 

 with a small proportion of binoxide of manganese works 

 well. The most satisfactory cells I have yet tried were 

 made by painting the lead plates with a coat of the brown 

 peroxide itself, which is obtainable in commerce, although 

 its cost is greater than that of red lead or litharge. 



