December 30, 1909] 



NA TURE 



259 



tion, but with a velocity slightly less than that of the 

 shell, the result being that, with respect to the shell, the 

 nucleus makes one revolution to the west in 952 years. 

 On this revolving nucleus the author assumes there are 

 projecting or " active " spots which in their motion come 

 under weak portions of the crust and cause earthquakes 

 and volcanic disturbances. On this basis he calculates the 

 positions of the active spots on the nucleus which have 

 during the last sixty years produced disturbances notified 

 by ships at sea in the tropical parts of the Atlantic. 

 According to the calculation, these active spots are now 

 nearly all collected under the region between longitude 

 35° and 41° W., and latitude 1° N. and 1° S., which should 

 therefore be a danger zone. It will be interesting to see 

 if further statistics support this theory. 



We have received from Lu-kia-pang, China — which now 

 .'■.erves as the magnetic observatory of the Jesuit fathers 

 of Zi-ka-wei — an interesting copy of the record of the 

 great magnetic storm of September 25, with some notes 

 tl-.ereon. The storm in China was of similar duration to 

 that experienced «n this country, and presented many 

 similar features, but the oscillations were of a much less 

 striking character. The ranges of the declination and 

 vertical force disturbances — about 50' and 0002 C.G.S. 

 respectively — were much less than in Europe. The range 

 in horizontal force, however, exceeded 0005 C.G.S., and 

 the excess may have been large, as the trace was off the 

 sheet during the greater part of the storm. About three 

 hours before the large disturbance began there was a 

 curious little movement, seen in all the elements, which is 

 described in the " Notes " as a precursor of the storm. 

 We understand that movements corresponding to the sup- 

 posed precursor are distinctly shown on the Kew curves, 

 so that whether related or not to the great storm they seem 

 to have been, like it, experienced all over the world. 



The dissociation of hydrobromic and hydriodic acids at 

 high temperatures is the subject of a paper by K. V. v. 

 Falckenstein in the current number of the Zeitschrift fiir 

 physikalischc Chemie. The method used is the statical one, 

 first employed by Lowcnstein, and is based on the fact 

 that at a high temperature platinum permits the passage 

 of hydrogen, but of no other gas. The action of the red- 

 hot metal may be roughly regarded as a filter, the pores of 

 which are so small that only the very small hydrogen mole- 

 cules can pass through. The gaseous hydrogen compound, 

 contained in a fused quartz tube and heated in an electric 

 resistance furnace, passes over a platinum bulb, the inside 

 of the latter being connected to a manometer. The pres- 

 sure of the hydrogen inside the bulb is in equilibrium with 

 the hydrogen outside the bulb arising from the dissocia- 

 tion. Data are given for three temperatures, 1024°, 1108°, 

 and 1222°, in the case of hydrobromic acid, and for two, 

 1022° and 1217°, for hydriodic acid. Bodenstein and 

 Geiger have measured the E.M.F. at 30° of the cell 

 Br, — HBr — Hj, and Haber has deduced a formula for the 

 relation between the amount of dissociation of the hydro- 

 bromic acid and the temperature. It is interesting to note 

 that the dissociation calculated from this formula, in spite 

 of the large temperature difference between 30° and 1200°, 

 is in very fair agreement with the experimental results 

 described in this paper. 



The sixty-sixth annual issue of the Medical Directory, 

 for iqio, published by Messrs. J. and A. Churchill (price 

 14s. net), includes several new features. It appears from 

 the numerical summary that there are 40,558 members of 

 the medical profession, the increase from 1909 to 1910 

 being 566. The directory includes, for the first time, a 

 NO. 2096, VOL. 82] 



section on the principal British spas and climatic health 

 resorts, by Mr. N. H. Forbes. Improvements have also 

 been made in the list of hospitals and other institutions 

 printed at the end of the London section of the directory. 



Messrs. Charles Griffin and Co., Ltd., have pub- 

 lished a si.xth edition of Prof. Grenville A. J. Cole's " ."Vids 

 in Practical Geology." Alterations have been made in 

 more than a hundred places, and the subject-matter has 

 in this way been brought up to date. While certain 

 modern restrictions in nomenclature have been introduced, 

 the limits of the names of rocks and fossil genera have, 

 as in previous editions, been kept as wide as possible. 

 Prof. Cole's book has been of signal service to very many 

 practical geologists since its first publication in 1890, and 

 in its latest revised form we have no doubt its sphere of 

 usefulness will be extended. 



OUR ASTRONOMICAL COLUMN. 



Hallev's Comet, 1909c.— As was briefly stated on p. 239 

 of our issue of last week, M. Deslandres has added to the 

 large refiector at Meudon a finder, fitted with a moving 

 reticle, which enables the instrument to be used for photo- 

 graphing any faint object moving in relation to the 

 surrounding guiding stars. The aperture of the large re- 

 flector is I metre, the focal length 3 metres, and an 

 exposure of five minutes, on December 6, 7, and 8, was 

 sutTicient to give a sharp image of the comet's central 

 portion. With an hour's exposure the comet was seen, on 

 the negative, as a nebulosity, elongated in the direction 

 opposed to the sun. The finder now in use has an aperture 

 of IS cm. (6 inches) and a focal length of 2-3 metres, and 

 may be placed on either side of the telescope to suit the 

 convenience of the observer, a suitable counterpoise of the 

 same form being employed on the opposite side. 



In conjunction with M. Bernard, M. Deslandres also 

 describes two spectra of the comet secured on December 6 

 and 8 with exposures of two hours and three hours re- 

 spectivelv. That the comet, on December 6, was already 

 emitting' its own radiations is shown by the appearance of 

 bright condensations at K 388 and X 391-45. ^^ '" More- 

 house's comet last vear. In addition to the nearly circular 

 nucleus, several curved rays, fainter than the nucleus and 

 having the appearance of antennee, were seen ; from their 

 direction it is diflRcult to account for these rays solelv on 

 the assumption that they are produced by solar repulsion. 

 A spectrum taken on December 13 shows the continuous 

 spectrum of the nucleus stronger and the condensations in 

 the ultra-violet larger, the latter radiations evidently 

 emanating from the nebulosity surrounding the nucleus. 

 There is also some evidence for the oscillations of bright- 

 ness observed at Greenwich {Comptes rendus. No. 24, 

 December 13). . 



Other visual observations of the comet are recorded in 

 No. 4377 of the Astronomische Nachrichten, where Prof. 

 A. A. "iwanow also has a paper describing his calculations 

 of the perturbations of the comet's path between 1835 and 

 iqio. His final elements give April 23, 19 10, as the prob- 

 able date of perihelion passage. 



An Interesting Sun-spot. — In No. 4377 of the Astro- 

 nomische Nachrichten M. Amaftounsky describes the 

 changes in detail which took place in a sun-spot first seen 

 on the sun's eastern limb on September 27 (September 

 15 O.S.). Six drawings which accompany the paper show- 

 how enormous were the changes, and M. Amaftounsky 

 directs special attention to a marked yellowish-green tint 

 which pervaded the bright tongues, or bridges, over the 

 nucleus and the bright edges of the penumbra. This was 

 not an optical coloration, and, according to the observer, 

 is a very rare phenomenon. 



Periods in the Variation of Latitude. — No. 8 of the 

 Bulletin Internalioual de I'Academie des Sciences de 

 Cracovie (October, p. 543) contains a resiim^. in French, 

 of a memoir by M. Jan Krassowski, in which the author 

 briefly discusses the results obtained by him in an analysis, 

 by Schuster's " periodogram " method, of the motion of 

 the pole. The data employed consisted of all the results 



