272 



KNOWLEDGE 



[December, 1903. 



lisrht and dark, and the chief one, first seen at the middle 

 of .Tune, has lieen watched at Bristol during the past five 

 mouths, and its mean rotation period has been as nearly 

 as possible lOh. 38m. There is indication that the motion 

 of this j)articular object has been slightly accelerated, but 

 the evidence is not conclusive on the point. The other 

 markings distributed along the same latitude show slight 

 differences of period, and at the end of September they 

 had become difficult objects. 



In June the princijial spot was large, and very much 

 brighter thau the light north-temperate zone in which it 

 ^yas placed. The usual observational discordances have 

 become apparent as regards tlie transit times, the form, 

 dimensions, and aspect of the marking. Barnard on June 

 23 found the length, E. and W., 2"-6.' H. C. Wilson, at 

 Northfield, Minn., on July 1 measured the length, 3"'93, 

 and wddth, 2"'36, while Graff on June 26 gave the propor- 

 tions .5" by 3". The sjiot is both followed and preceded 

 by dusky patches stretching from the north equatorial belt 

 to the polar shading. As seen by Wilson on July 1 it 

 appeared surrounded by a narrow dai'k line, but the 

 observer suggests that this may have been the effects of 

 contrast. The north latitude of the spot, according to a 

 measure liy Barnard on June 23, was 36°'4, while Wilson 

 determined it on July 1 as 31°1. 



Present indications are that the disturbance has, in its 

 Triain features, practically subsided. Its lessons cannot 

 fail to be of considerable interest. It has afforded the 

 clearest proofs of a north-temperate current rotating 23^- 

 minutes slower than the equatorial current as determined 

 by Prof. Hall from his spot of 1876-7. A comparison of 

 the relative velocities leads us to the following cimous 

 deductions. The equatorial spots are moving so much 

 faster than the noi-th-temperate spots that they gain some 

 800 miles per hour upon them, and complete a circuit of 

 Saturn relatively to their positions in about 12 days. A ter- 

 restrial hurricane is supposed to have an extreme velocity of 

 about 100 miles per hour, but the wind currents on Saturn 

 appear to be incomparalily swifter. And the rapid 

 equatorial drift on Saturn is probably persistent within 

 small limits of variation like the equatorial current of 

 Jupiter, which, during the last 2.'> years, has only varied 

 between 9h. .50m. and 9h. 50im. 



On the latter planet the ordinary north-temperate spots 

 rotate in 9h. 5.5m. 54s., which is about 5^ minutes slower 

 than the equatorial spots. Both on Jupiter and Saturn, 

 therefore, the mobile vapours on or near the equator are 

 streaming along with abnormal velocity, outstripping 



suitable for exhibition than for sedulous research. In any 

 case it is to be hoped that he will now receive more fitting 

 recognition, for his belts and occasional spots merit as 

 much attention as the variegated scenery of Jupiter or 

 the wonderful and complicated caualiform aspect of Mars. 



Previous oliservations suggest that the rotation of the 

 equator of Saturn is lOh. 145m., of the south-temperate 

 region lOh. 25m., and of the north tempei-ate region 

 lOh. 38m. But the materials are altogether too scanty for 

 safe deductions. Many new observations are required of 

 well-marked equatorial and south-temperate spots. We 

 may have to wait vears for the apparition of these, for 

 Saturn's aspect is often serene and smooth, without any 

 obvious irregularities in the belts and zones. 



Postscript, Nov. 15. — Including my latest observations 

 here with a lO-inch reflector, powers 312 and 332, the 

 mean rotation periods of three of the best observed spots 

 on Saturn work out as follow : — • 



Interv.al of 



Object. Observations. Rotations. Period. 



Days. h. m. s. 



Barnard's White Spot 138 310 10 37 o2-4 



White Spot 132 295 10 37 420 



Dark Spot 120 270 10 37 564 



The period appears therefore to be a little less than 

 lOh. 38m., and bears out the suggestion previously made 

 that the velocitv has been accelerated. 



THE CHEMISTRY OF THE STARS. 



VI.— STARS OF THE THIRD AND 



FOURTH TYPES. 



By A. Fowler, f.e.a.s. 



Secchi found that stars of a decidedly orange or red tint 

 were generally distinguished spectroscopically by the 

 presence of " flutings," and he further recognized that 

 such stars were easily divisible into two groups. In one 

 of them, constituting his Type III., there are dark flutings 

 which degrade towards the red end of the spectrum, while 

 in the other group, which he designated Type IV., the 

 flutings fade off towards the violet. In both types the 

 blue end of the spectrum is very feeble, probably in part 

 through deficient continuous radiation, and jiartly on 

 account of excessive absorption, and it is to this fact that 

 the redness of the stars is to be attributed. 



What is meant exactly by a fluting may be gathered 

 from Fig. 11, illustrating the fluted speetrtnu of carbon, 



11. — Flutings of Cyanogen and Carbon. 



other markings to N. and S., and also, probably, the actual 

 rotatory movement of the immense spheres below. There 

 may be occasional exceptions, it is true, as, for instance, the 

 very rapidly moving dark spots which temporarily marked 

 the north- temperate region of Jupiter in 1880 and 1891. 



The closer scrutiny of Saturn in future years is desirable, 

 and it seems well assured from the interest awakened by 

 the prominent signs of activity recently displayed on the 

 planet's surface. The investigation is" a promising one. 

 It may appear curious, on reflection, that comparatively 

 little has been already accomplished in elucidating the 

 visible surface phenomena of this wonderful orb, forming 

 as he does the most charming picture in the sky. Perhaps 

 Saturn has sometimes been regarded as an object more 



as exhibited in the sjiectrum of the electric arc between 

 carbon poles. The spectrum consists of a numljer of 

 groups of flutings, or shaded bands, each simple fluting 

 commencing with a well-defined " head," and being 



Fig. 12.— Enlarged Yiew of Fluting X 3S83. 



followed by closely-ruled fine Unes which gradually get 

 feebler and further apart as the leader is left behind. 



