50 



NATURE 



[NOVEMDER lO, 19 lO 



.iples, of the origin of the diurnal variations of the trade 

 wind over the South Atlantic gives results which are 

 hopeful, but not final. 



The well-known observatory on Mount Vesuvius was 

 founded in the days of the Kingdom of Two Sicilies, and 

 was taken over by the Government at the time of the 

 unification of Italy. The work that it has done under 

 the direction of Prof. Palmieri, and latterly Matteucci, is 

 well known; but in a plea put forward in the Atii dei 

 Lined, xix., 3. Dr. Carlo dei Stefani states that the 

 institution has been hampered by the want of a more sub- 

 stantial subsidy from the State, and he further directs 

 attention to the desirability of establishing a much more 

 extensive institution for the study of Vesuvius in all its 

 aspects. It is pointed out that since the observatory was 

 founded eveiy branch of science has advanced enormously, 

 that the study of volcanoes plays an important part in 

 geology and geophysics, and that Vesuvius, from its 

 situation as well as from our intimate knowledge of its 

 past history, offers exceptional facilities for systematic 

 study. In such an institution the departments of geology, 

 mineralogy, chemistry, and physics should all be repre- 

 sented on the staff. 



The geometry of the triangle occupies a somewhat 

 unique position in mathematics, leading as it does to a 

 large number of results which appear to be capable of 

 being added to almost without limit, which do not require 

 the employment of advanced methods for their study, and 

 have the further interesting peculiarity — perhaps not 

 altogether a disadvantage — that they can be studied with- 

 out afterthoughts as to probable utilitarian applications. 

 We have received two papers on this subject. One is by 

 Mr. W. Gallatly (London : Francis Hodgson, price 

 2S. 6d.), dealing with Lemoine and Brocard points, 

 angular and tripolar coordinates, pedal and antipedal 

 triangles, the medial triangle, Simson's line, the ortho- 

 pole, and orthogonal projection. The second, by Mr. 

 W. H. Salmon, is a note reprinted from the Quarterly 

 Journal of Pure and Applied Mathen^atics, dealing with 

 the Omega and Omega-prime lines and the y line. These 

 lines are defined by the property that if O be any point 

 in the plane of a triangle, and the lines OA, OB, OC be 

 rotated through a constant angle, they will, for certain 

 angles of rotation, meet the sides taken in order in three 

 points lying on a straight line, these lines being the lines 

 in question. 



Prof. L. Palazzo has sent us a copy of his " Misure 

 Magnetiche fatte in Sardegna nel 1892," extracted from 

 vol. xxiv. of the Annali of the Italian Meteorological 

 Service. This volume belongs to the year 1902, but the 

 chronological order has not been observed in the publica- 

 tions of the Italian Meteorological Service — some of which 

 are much in arrears — so that an account is only now 

 published of the magnetic survey of Sardinia made by 

 Prof. Palazzo in 1892. Sixteen stations were occupied, the 

 observations at which are described in minute detail, the 

 results being embodied in a chart. No really large local 

 disturbances were detected, but some minor disturbances 

 were noticed, especially towards the north-west of the 

 island. Besides a full description of the observational 

 methods and reductions, there are descriptions, with plates, 

 of apparatus for determining the temperature and induc- 

 tion coefficients of collimator magnets, with which very 

 consistent results seem to have been obtained. 



In the May number of the International Bulletin of the 

 Academy of Sciences of Cracow Prof. Smoluchowski, of 

 the University of Lemberg, gives an account of some 



NO. 2 141, VOL. 85] 



I measurements he has recently made of the heat Qonduqtlv 



ties of fine powders, and the influence of the size of the 

 , grains and the state of the gas between them on the con- 

 i ductivity. His apparatus is in principle identical with 

 I that used by Kundt and Warburg in their measurements 

 of the heat conductivities of gases. It consists of a 

 thermometer the bulb of which is surrounded by a tube 

 nearly concentric with it, the space between the bulb and 

 1 tube being filled with the powder and connected to a 

 Gaede pump, so that it can be filled with a gas or 

 I evacuated. Whatever the nature of the powder, the con- 

 ductivity through the gas between the grains is found to 

 ; diminish rapidly as the pressure of the gas is reduced, 

 I and for granular, as distinguished from spongy, powders 

 1 its dependence on the pressure may be calculated by the 

 j aid of the kinetic theory of gases if the surface resi- 

 ahce, which depends on the mean free path of the mol 

 cules of the gas, is taken into account at the low 

 pressures. 



Copies have reached us of the volumes of magnftic data 

 recorded during 1905 and 1906 at the observatories of the 

 U.S. Coast and Geodetic Survey. There are five of these 

 observatories, viz. at Cheltenham, Baldwin, Sitka, Hono- 

 lulu, and Vieques (Porto Rico). The Cheltenham volume 

 is dated 1909, the others 1910. Thus the delay in publi- 

 cation seems hardly accounted for by the inclusion of two 

 .years' data in the same volume. The procedure followed 

 and the mode of presenting the data are closely alike at 

 all the stations. Full particulars are given of all th" 

 hourly readings and of the daily maxima and minima, but 

 only the ten quietest days of each month are employed 

 for deducing the diurnal inequalities. Each volume con- 

 tains a table of the principal magnetic disturbances, and 

 some of the curves showing them are reproduced on a 

 reduced scale. Except at Cheltenham, the times shown on 

 the curves are G.M.T., thus facilitating intercomparison. 

 but the times of commencement, &c., given in the text 

 are in local mean time. The stations are now all pro- 

 vided with a complete outfit of Eschenhagen magnet< 

 graphs, including vertical force instruments. The troubl' 

 experienced — discontinuities in the trace, changes of seal- 

 value, drift of trace across the sheet, and general instabiliiv 

 — are described in some detail, and though most prominent 

 in the vertical force instruments, seem by no means con- 

 fined to them. Even the declination instrument gave 

 serious trouble at Baldwin, leading to considerable loss of 

 trace. One cannot but experience a doubt whether ;i 

 more stable and less sensitive type of instrument would 

 not have been preferable, especially at the less accessible' 

 stations. In addition to other troubles, Sitka suffered 

 from an outbreak of dry rot, which necessitated a lari^ 

 amount of internal structural alteration in the magnet* 

 graph room. This led, however, practically to no loss < : 

 trace, the magnetographs being accommodated during th' 

 alterations in a temjxirary building. In addition to mac- 

 netic data, there are particulars of the seismic movement -^ 

 recorded by seismographs, mostly of the Bosch-Omori 

 pattern. 



A LIST of observing stations and particulars of th- 

 apparatus employed in connection with the Michael Sais 

 North Atlantic Deep Sea Expedition, 1910, has just been 

 received. An article by Dr. Johan Hjort describing th- 

 work of the expedition is given in another part of th- 

 present issue. 



Messrs. Henry Sotheran and Co., 140 Strand and 

 43 Piccadilly, London, have issued a new classified cata- 

 logue (No. 709) of second-hand books on geology, 



