November 14, 1895] 



NATURE 



33 



Institute to be tested amounted last year to 1 1,656, of which 



10,005 were clinical thermometers. A small charge is 



made for work done for the trade, but the receipts from 



this source of revenue do not exceed ;^ 1000. Incident- 



'ally, in connection with this work, there is a large amount 



'of original investigation, and the staff employed are all 



men of proved scientific ability. New methods for 



obtaining more correct results and greater accuracy in 



^measurement are constantly being investigated, and to 



{this extent Section II. is equally with Section I. a 



laboratory of research. The experiments in Section II., 



•however, are all directed towards the more accurate 



testing of instiaiments of precision. Some of the work 



tdone in this section is undertaken at the request of the 



jtaff of the Research Laboratory, and in connection with 



le experiments in pure science. 



This Imperial Institute is under the immediate control 

 of a Curatorium or Council, consisting of Professors of 

 the University and Polytechnic, of engineering and tech- 

 nical experts, and of heads of industrial firms, presided over 

 by a member of the Government. The selection of mem- 

 bers of the staff, and permission to work at the Institute, 

 rest with the Council. At first, applicants for admission 

 were required to have obtained their Doctor's degree ; but 

 no such rule now holds. The ability to work, and the inten- 

 tion of prosecuting some original investigation previously 

 approved by the Council, is a sufficient qualification. 

 Each application for admission is considered on its 

 merits. The Physical-Technical Imperial Institute is the 

 crown of the series of coordinated Institutions which 

 afford facilities for technical instruction in physical 

 science, and opportunities for advanced research. In the 

 city of Berlin are well represented the various educational 

 agencies which have contributed so largely to the great- 

 ness of Germany ; and the improvements which have 

 been made of late years in the lighting and sanitation, in 

 the postal and telephone arrangements of Berlin, are so 

 many practical indications of the value of the education 

 which the State and the city jointly provide. The 

 Physical Institute is literally a temple dedicated to 

 science, and its two divisions correspond with the two- 

 fold character of all scientific work — that which is under- 

 taken with the sole object of widening the area of know- 

 ledge, and that which enables knowledge to be applied 

 to the useful purposes of life. Philip Magnus. 



THE PLANE T JUPITER. 

 'T*HIS bright planet now rises more than two hours 

 ■'■ and a half before midnight, and as his northern 

 declination is about iSj'^, he attains an altitude of about 

 57'' when southing at about 5h. 15m. a.m. His apparent 

 equatorial diameter this evening (Nov. 14) will be nearly 

 4o""5, and is increasing daily, so that by the end of the year 

 it will be 45""6, when the planet will be visible nearly all 

 night, and remain above the horizon during a period of 

 1 5^ hours. He will arrive at opposition to the sun on 

 January 24, 1896, and will then be displayed under the 

 best conditions.- 



To those, however, who are disposed to study the com- 

 plex and variable features exhibited by the belts, the pre- 

 sent is an important time, for it is advisable that such 

 markings should be watched during long periods, and that 

 a large number of their transits should be recorded. 

 Their individual rotation periods may then be ascertained, 

 and the differences determined, together with the fluctua- 

 tions of speed affecting the same objects. Details of this 

 character can only be correctly derived when the observa- 

 tions are numerous and extend, at least, over a fairly long 

 period of time. Materials of the kind alluded to, ob- 

 tained in the early part of the opposition, are of special 

 value for comparison with the observations made at the 

 time of opposition, and with the terminal ones which may 



NO. 1359. VOL. y:,'\ 



be secured in the evenings of June 1896, just before the 

 planet leaves us for a season. 



The features of Jupiter, though liable to certain changes, 

 are yet, in some of their leading characteristics, remark- 

 ably durable. Like the spots on the sun, many of the 

 markings on the planet disappear and reappear under 

 very similar aspects. In fact, we are not without evidence 

 that a certain degree of periodicity regulates the visi- 

 bility of certain spots on the disc. In 1870 there was an 

 eruption of dark spots along a belt in about 25° north 

 latitude. In 1880 the phenomena appear to have re- 

 curred, for the same belt became studded with black spots, 

 and in 1891 similar appearances were repeated. These 

 markings are remarkable, as possibly indicating a period- 

 ical recurrence at intervals of about ten or eleven years. 

 But it may be gravely doubted whether, in the present 

 state of our knowledge, the materials exist for suitably 

 investigating the question as to cyclical changes in the 

 Jovian spots. The individuality of observers must affect 

 the matter to a considerable degree, as their drawings 

 and descriptions of the same features are seldom in 

 agreement. 



In recent years, the great red spot has not been so 

 much observed as formerly. It has lost its striking 

 character and its novelty, and planetary students have 

 somewhat neglected it for newer objects more readily 

 within reach. During the last ten years the mean 

 rotation period of the spot has been 9h. 55m. 41s. ; 

 but it has shown some irregular variations. The slacken- 

 ing motion of the spot which operated so perceptibly 

 between 1879 ^"d 1885, and added seven seconds to the 

 rotation period, appears to have been checked in the 

 latter year, and the rate has been pretty evenly main- 

 tained since that time. 



As to the visible aspect of the spot, it is now extremely 

 faint, and can only be discerned on a good night of 

 definition. Its feeble outlines are generally lost amid 

 the very dark and well-marked boundaries of the belts 

 in its immediate vicinity. But on a good night it is 

 seen as a pinkish discolouration of the bright zone out- 

 lying the great southern equatorial belt, though its 

 beautiful oval outline is distinguished with difficulty. 



One of the interesting features of recent oppositions 

 of Jupiter has been the series of dark and white spots 

 plentifully arranged along the northern side of the great 

 northern equatorial belt. These markings move swifter 

 than the red spot, but not much so, for their period is 

 9h. 55m. 35s., or only six seconds less. They show 

 changes, for sometimes one may be seen exceedingly 

 dark, if not absolutely black, and just like a satellite- 

 shadow in transit ; but in a week or two a great de- 

 cadence of tone may have affected it, and it appears 

 scarcely darker than the belt on which it lies. These 

 markings, so prominently fringing the northern belt, have 

 certainly been visible during the last ten years. In 1885 

 I found their motion about eight seconds swifter than 

 that of the red spot, but there were irregularities. 

 Different spots, though in the same longitude and, 

 probably, of the same character, do not yield coincident 

 times of rotation, nor does any one object maintain 

 exactly the same rate during a long period of time. The 

 current in which they are situated, and by which they 

 are transported to different longitudes, evidently suffers 

 inequalities of speed, which are probably due to local 

 disturbances underlying it. 



These features of the northern belt are still very pro- 

 nounced. On the morning of September 27, I observed 

 two very dark spots projecting north from the belt and 

 preceding the red spot at intervals of about four and two 

 hours. The red spot follows Mr. Marth's zero meridian 

 (System II.) by about seven minutes, but I have only 

 obtained two observations since Jupiter has been visible 

 as a morning star, and neither of these was very 

 satisfactory. 



