148 



KNOWLEDGE & SCIENTIFIC NEWS. 



[July, 1904. 



Jvipiter, 



It is fortunate that in recent years Jupiter has been 

 studied attentively at every opposition. The markings have 

 been watched from the time when the planet rose about 

 two hours before the sun to the time when he set about two 

 hours after it. In fact, the observations have generally 

 ranged over nine months of the year, and have been only 



*x (*/Cy //(" 



/ 



C^^it/ii.r: 1: A-i 



discontinued when Jupiter approached near the sun- 

 Since iSi)8 we have gained a useful insight into the rates 

 of motion of the various currents, and of the positions 

 and changes of the belts. This continuous study of the 

 Jovian surface must be maintained. It will ultimately 

 prove of great value in elucidating the changes taking 

 place in the velocity and aspect of the various spots, and 

 it may be the means of revealing periodicity either as 

 regards the motion or appearance of certain features. 



In and since the year 1898, the writer, at Bristol, has 

 found the rotation periods of the chief currents as 

 under : — 



Somewhat similar observations and reductions have 

 been made in recent years by Professor G. \V. Hough, 

 Captain Molesworth, Rev. T. E. R. Phillips, and ^Ir. 

 A. S. Williams. When the work has further progressed 

 through future years it will be important to compare all 

 the accumulated materials to see whether some useful 

 deductions cannot be made from them. 



The mean periods of rotation from all observations in 

 the table are : — N. temp, spots = 9 h. 55 m. 53 s,, 

 N. trop. spots = 9 h. 55 m. 30 s., Equatorial spots = 

 9 h. 50 m. 26 s., Red spot = 9 h. 55 m. 41 s., S. temp, spots 

 = 9 h. 55 m. 19 s. Thus the N. temp, spots move slower 

 while the equatorial spots move quicker than any others 

 observed in recent years. Of course, the most interest- 



ing object on the planet is the great red spot which for a 



long period has been so faint as to have scarcely merited 

 that dtsignation. But it was a little p'ainer during 1903 

 than in the few preceding years, and possibly it will be 

 still darker during the present summer. The following 

 are a few times when this marking will be onor very near 

 the planet's central meridian. If the spot should not be 

 visible the conspicuous hollow in the S. equatorial belt 

 will show its position, and the time of transit of the latter 

 object should be taken. 



Date Transit of Red Spat. 

 1904. h. m. 



June 2 15 25 



7 '4 34 



9 . . . . . . . . 16 12 



14 15 21 



19 14 29 



21 16 8 



24 

 26 



13 38 

 IS 16 



To the \arious other markings particular reference 

 need not be made. In recent years they have, however, 

 been very numerous, and many of them conspicuous. 

 Any spots which may appear near the poles of the planet 

 should be watched with great attention. 



■ W. F. Denning. 



The Leg ©Liid Foot of a. 

 Spider. 



At the con\ersa/iiMie of the Royal Society this photo- 

 micrograph, which forms our full-page illustration, was 

 h;liQwn, with many others. The aim of the exhibitors, 

 Messrs. Arthur M. Smith and Richard Kerr, w.is to 

 point out the value of direct photography on to a \i by 

 10 inch plate and to show its advantages over enlarge- 

 ments made from smaller neg-atives. The details ob- 

 tained at once by combining an unusually large camera 

 u ith a monocular microscope are greater than those 

 secured by ordinary amplifying methods. Tliis illustra- 

 tion represents aiv enlargement of 260 diameters and 

 has been obtained by a one-inch objective and a l(x;al 

 length of 37 inches approximately. The negative has 

 received no touching up whatever. 



The expyedit'ons at present jiJIoat and organising for 

 discoveries in the North Pole regions, as summarised 

 by the American Inventor, are (1) that of the Russian 

 r.aron E. Toll, wlio left the island of Kotelnoi, in the 

 New Siberian group, over a year ago, and has not since 

 Ijeen heard from ; [2) the new Ziegler expedition, com- 

 manded by Captain John Haven, which left New York 

 last spring, reached Tromsoe near the end of July, and 

 upon attempting to make Frtmz-Josef Land met with 

 obstacles which have deferred further attempt till next 

 spring ; (3) an expedition projected by Captain Drake, 

 who will sail for Madivostok and Point Barrow in 

 .Vkiska, whence he will later make a "dash for the 

 Pole ■' ; and (4) Lieutenant Peary's new venture, which 

 was :mnounced in the early part of September. The 

 Norwegian Amundsen is supposed to be among the 

 island.s of British North .America, in search of the 

 magnetic pole. 



