January 4, 1894] 



NATURE 



229 



James Tolson ; secretary, Mr. Wm. Soutter. Section J— 

 Mental Science and Education : Vice-presidents, his Grace 

 Archbishop Dunne, Mr. G. J. Anderson, M.A., and Mr. D. 

 Cameron. 



An earthquake shock was felt in Shepton Mallet, Somerset, 

 and neighbourhood on December 30, about 11.30 p.m., and 

 another shortly after midnight. The direction of motion of the 

 waves was apparently from north to south. Prof. F. J. 

 Allen sends us the following description of what was noticed 

 by some friends of his. " At about 11.20 p.m. a shock was felt 

 by three persons in one house ; and about an hour later a 

 second and more severe shock was observed by two of these 

 persons. In another house, a quarter of a mile distant, three 

 distinct shocks were felt by several persons. Both these houses 

 are situated on the south side of the valley, whereas the reports 

 published in the papers refer more particularly to movements 

 observed on the north side. For those who are not acquainted 

 with the district, I would mention that the strata (Carboniferous 

 limestone, with overlying Trias, Lias, and Oolite) are very much 

 disturbed, and present many interesting studies of horizontal as 

 well as vertical faulting. It is just the kind of spot in which 

 one might e.xpect to have superficial movements occurring from 

 time to time." 



A LETTER fromiProf. S. J. Bailey, of the Harvard College 

 Observatory, to the editor ol La Bolsa, published at Arequipa, 

 Peru, gives an a'-count of the establishment of the meteorological 

 station on the summit of the Misti, in the Peruvian Andes, at an 

 altitude of 19,300 feet above sea level, this being at present the 

 highest observatory in existence. The fatigues undergone by 

 observers ascending the conical peak from Arequipa are such as 

 to render exact observations impossible, and it was therefore 

 found necessary to construct a nuile-path to the summit from a 

 stone hut erected at an elevation of about 16,000 feet. This hut 

 was erected on the north-east slope, being the most accessible 

 side of this peak, which maintains its aspect of an isolated 

 symmetrical cone from all points of view. On September 27 

 the summit was reached by Prof. Bailey, his assistant, several 

 Indians, and two mules. The latter could hardly be made to go 

 more than twenty paces without a rest. On October 12 the 

 summit was revisited with two members of the Arequipa 

 observatory, twelve Indians, and thirteen mules carrying 

 materials for erecting two huts, and the registering meteorological 

 instruments, comprising a barograph, a thermograph, several 

 mercury thermometers, an hygrometer and anemometers. Each 

 of the registering instruments works for ten days, and a member 

 of the observatory will visit the station three times a month. 

 A store of provisions is kept at the stone hut, and of the wooden 

 huts at the top, one, provided with double wooden walls, is 

 intended for the observer, the other for the instruments. 



With regard to meteorological work in Australia, Sir Charles 

 Todd remarked at the last meeting of the Australasian 

 Association for the Advancement of Science, that in New 

 South Wales there were 175 meteorological stations and 

 1063 rail-, gauges; in Victoria, 31 meteorological stations and 

 515 rain gauges ; in South Australia, 22 meteorological stations 

 and 370 rain gauges. In Australia there were 385 meteoro- 

 logical stations and 2580 rain gauges. During the last four 

 years the forecasts issued in South Australia have been justified 

 to the extent of 73 per cent., partially justified 20 per cent., and 

 wholly wrong 7 per cent. 



The radius of curvature of the cornea, together with the in- 

 dices of refraction of the various refractive media of the eye, 

 constitute the experimental data for determining the most im- 

 portant points a.bout the eye. Drs. H. C. Chapman and A. P. 

 Brubaker have measured this radius in fifty individuals by means 

 NO. 1262, VOL. 49] 



of the ophthalometer (Proc. Acad. Nat. Sci., Philadelphia, 

 1893, p. 349), and they have found that in the average young 

 man it amounts in the horizontal meridian to 7 '797 mm., and in 

 the vertical meridian to 7 '552. 



The Director of the Central Meteorological Observatory of 

 Mexico, Seiior M. Barcena, has published an interesting pam- 

 phlet on the climate of the city of Mexico, based on the hourly 

 observations of sixteen years 1877-92. Mexico, from its 

 position of 7431 feet above the sea, and latitude 19°, might be 

 supposed to be subject to great extremes of temperature, but as 

 one geographical element neutralises the other, the result is a 

 temperate and agreeable climate. The mean annual temperature 

 is 59'7) and the monthly means vary from 53°'6 in December to 

 64°"6in May. The absolute maxima in the shade vary from 

 73°'4 in December to88°"9 in April, while the absolute minima 

 vary from 28° '9 in December to 46° "8 in August and September. 

 The greatest daily range amounted to 41^ in the month of 

 March. The mean annual rainfall amounted to 23 '8 inches, the 

 wettest months being June to September ; the greatest fall in 

 one day was 2'5 inches in August 1888. The prevalent wind 

 is north-west, which blows during most part of the year, and is 

 the coldest and wettest quarter. The strongest wind blows 

 from the north east ; the greatest hourly velocity observed 

 during the sixteen years was about 56 miles per hour. 



A DETAILED investigation of the properties of mirror silver 

 chemically precipitated on glass is published by Herr H. 

 Llidtke in Jl'iedemann's Annalen. The three modifications of 

 silver obtained in the wet way, termed by H. Vogel the arbor- 

 escent, the powdery, and the niirror variety respectively, have 

 been recently enriched by Mr. Carey Lea through his discovery 

 of colloid silve . Herr Llidtke thinks that this last variety and 

 mirror silver are closely allied ; that the latter, when newly 

 formed, is indeed identical with the former. The electrical 

 resistance of several varieties of mirror silver decreases con- 

 siderably with their age. No such decrease was, however, ob- 

 served in the case of mirrors produced by Martin's process or by 

 that of Liebig, i.e. reduction by means of milk-sugar. On in- 

 troducing a pole of ordinary silver and one of allotropic miiror 

 silver into a weak acid or salt solution, and closing the circuit, 

 a current was obtained indicating a difference of potential of 

 about O'l volt between the two varieties, the allotropic variety 

 being the positive pole. These conditions were reversed if the 

 solution was one of silver nitrate, but the difference of poten. 

 tial was less. Lehmann's surmise that the precipitation of the 

 mirror on the glass is due to a thin layer of sodium silicate, was 

 invalidated by precipitating it on mica, porcelain, quartz, and 

 platinum by the same methods. 



The Philosophical Magazine for the present month contains 

 a paper, by H. Nagaoka, on the hysteresis attending the change 

 in length produced by magnetisation in nickel and iron. The 

 author at first used the interference fringes produced between a 

 plano-convex lens and a plate of plane glass attached to the end 

 of the rod under examination to measure change in length. He 

 found, however, that it was impossible to keep the temperature 

 of the apparatus constant during the time necessary to make an 

 observation, and also that there was considerable difficulty in 

 counting the number of fringes displaced. To overcome the 

 lemperature difficulty the author has made use of the principle 

 of the gridiron-pendulum, and has by this means succeeded in 

 almost entirely overcoming this difficulty. In place of the 

 interference bands he uses an optical lever, that is, a mirror 

 fixed to a small base, to which are attached three needle points, 

 two of these rest in a grove on the base-plate of the in- 

 strument, while the third rests on a small glass plate fixed to 

 the end of the iron or nickel rod. The rod was placed along 

 the axis of a solenoid which lay in a horizontal position pointing 



