228 



NA TURE 



\_yari. 6, il 



has separately collected particulars of sixty-one spots, 

 held, with more or less of probability, to have presented 

 themselves afresh after making the circuit of the sun, and 

 hence to be available as guides to the period and law of 

 its rotation. From these data he constructed a curve 

 (Plate XVI. Fig. 2) showing the variations in the rate of 

 spot-displacement with varying latitude, the perfect sym- 

 metry of which on either side of the sun's equator testifies 

 to the absence of any systematic difference in this respect 

 between the hemispheres. From the curve were derived 

 three distinct formulas of the solar rotation, all fitting 

 perfectly with the observations within the parallels of 30^, 

 but diverging widely in their results for high latitudes. 

 For example, No. I. gives for the region close to either 

 pole a period of just 33 days ; No. III. of a little over 

 40; No. IT. of 55'8 days. From Carrington's formula, 

 Ur. Braun deduces a polar period of 3086 days ; Faye's 

 implies one of 32 ; .Sporer's actually reverses the direc- 

 tion of change beyond the spot-zones, indicating a recovery 

 of velocity towards the far north and south, and a period, 

 in latitude 90°, of no more than 25'i days — about the 

 same which prevails in parallels of 10°. It may be worth 

 remarking, as at least a coincidence, that almost precisely 

 this rate of motion was inferred by Father Secchi (very 

 doubtfully, it is true) from observations of relatively stable 

 prominences near the pole. Nevertheless, a survey of 

 the discrepancies tabulated by our author can hardly fail 

 to inspire a profound distrust of empirical formula:, and 

 still more of the risky process termed " extrapolation." 



The swiftest-moving spot noted by the Kalocsa observers 

 was situated 1° 20' north of the equator ; its estimated 

 daily displacement of 868' bringing about the completion 

 of its circuit in 24'88 days. The most sluggish was in 

 south latitude 29° 38', and gave a period of 26'5 days. 

 As might have been expected, considerable irregularities 

 are apparent ; yet not more than might reasonably be set 

 down to uncertainties of observation. A much higher 

 degree of accuracy must, however, be reached before the 

 mean rate of motion proper to each parallel can be at all 

 satisfactorily ascertained. This mean rate is itself, in 

 Sporer's view, subject to cyclical change ; and his observa 

 lions during the years 1 861 -i 871, as compared with 

 Carrington's during seven preceding years, disclosed per- 

 sistent differences not easily accounted for. Dr. Braun's 

 results, on the other hand, agree quite as well as could be 

 expected with those of the English observer. A further 

 complication is introduced by what may be called the 

 individual caprices of spots. Each soot has probably a 

 velocity of transport peculiar to itself, depending upon the 

 circumstances of its origin ; this velocity is certainly 

 subject to accelerations connected with the processes of 

 its development. These accelerations (for the change of 

 motion is always in a forward direction) are shown, in 

 Prof. Sporer's recent communication to the Physical 

 Society of Berlin, to be very considerable ; they are 

 beyond question highly significant ; yet they emphasise 

 our disadvantage in being compelled to rely upon such 

 unstable phenomena for all our knowledge regarding that 

 most important datum — the rate of the sun's revolution 

 on its axis. 



The Kalocsa solar observations were made at a critical 

 period. They cover the whole of the prolonged maximum 

 which culminated near the close of 1883, and disclose or 

 confirm very satisfactorily some of its characteristics. 

 Dr. Braun has depicted in a remarkable curve the 

 progressive changes in the mean latitude of the spot- 

 zones during the years 1880-84. Their continuous ap- 

 proach to the equator at once strikes the eye ; but 

 superposed upon the line of uniform descent is a series 

 of minor oscillations with a period of about a year, and an 

 amplitude of fully 2", which seem too regular and strongly- 

 marked to be the mere effect of accident. This feature is 

 quite novel and deserves attention. 



The general rule that the long series of spots comprised 



within each cycle break out first in high latitudes, and 

 become extinct close to the equator, was first observed by 

 Carrington, and may now be regarded as fully established. 

 Ordinarily, the maximum occurs when the mean latitude 

 of the zones is 16° or lS°, the energy of the disturbance 

 diminishing as they close further in. But the retarded 

 character of the recent crisis was significantly attested by 

 the fact that it did not reach its height until the closing 

 in had proceeded much further than usual. In 1882, 

 when the maximum was due, the average latitude of spots 

 was (from Dr. Braun's curve) about 16" ; whereas, at the 

 close of 1883, when the maximum actually occurred, it 

 was no more than !i'. It would seem as if the punctual 

 and duly prepared completion of the outburst had been 

 frustrated, and its stored-up energy spent upon an 

 abnormal protraction of the maximum. 



It might even be said that the perturbation thus indi- 

 cated affected chiefly, or solely, the southern hemisphere 

 of the sun. Although the respective sum-totals of spots 

 observed at Kalocsa north and south of the equator 

 eventually almost exactly balanced each other, large tem- 

 porary discrepancies were manifest. The northern hemi- 

 sphere displayed in 18S0 an excess of activity, still more 

 conspicuous in the ensuing year. Southern spots, on the 

 contrary, outnumbered northern in 1882 to the extent of 

 S per cent, and in 1883 in the proportion of nine to five. 

 Dr. Braun adds the remark that each hemisphere would 

 almost seem to have completed its cycle of change inde- 

 pendently of the other, the northern maximum having 

 occurred late in 188 1, while the southern was postponed 

 for two further years. The cause of perturbation should, 

 in this view, be localised in the southern hemisphere. 



A. M. Clerke 



NOTES 

 O.N November 10 last, an important meeting of intercolonial 

 delegates was held at the rooms of the Royal Society, Sydney, 

 for the purpose of forming an .\ustralasian Association for the 

 Advancement of .Science. There were delegates from all the 

 principal scientific Societies of Australia, and they seem to have 

 had no difficulty in arriving at a decision on the questions they 

 had met to discuss. On the motion of the chairman, Mr. 

 Russell, it was agreed that an association of the scientific 

 Societies of Australasia should be formed under the name of 

 " The .Australasian .\ssociation for the Advanceoient of Science." 

 It was also resolved that the rules of the British Association 

 should be adopted, and that the first meeting of the Australasian 

 Association should be held in Sydney in the first week ;of 

 September 1888. This date was fixed because it will be the 

 liundredth anniversary of the foundation of the colony of New 

 South Wales. 



Mr. H. N. Ridley, of the British Museum, intends to make 

 an expedition to the island of Fernando Noronha lor the purpose 

 of investigating its natural history. The funds tor the expedition 

 have been supplied by the Royal Society, and Mr. Ridley hopes 

 to be able to start at the end of r ebruary. The marine flora 

 and fauna were collected by the Challenger Expedition, but owing 

 to the fact that the island is a Brazilian penal settlement, no 

 naturalists have hitherto b=en permitted to make collections 

 therein. The Trustees of the British Museum have obtained from 

 the Emperor of Brazil the necessai^ permission for Mr. Ridley's 

 exploration of the island, which, from what little is known of it, 

 and from its geogi-aphical position, promises to be of exceptional 

 interest from a natural history point of view. 



The death is announced, at Victoria, British Columbia, of 

 Dr. \V. F. Tohnie. Dr. Tolmie's name has been favourably 

 known to ethnologists for many years in connection with his 

 researches respecting the Indian tribes of British Columbia and 



