58o 



NA TURE 



[April 19, 1894 



Vatican Observatory, Rome. Mr. A. W. Clayden ex- 

 hibits a number of enlargements of cloud photographs 

 taken by reflection from a black glass mirror, and he also 

 shows the camera by which they were obtained. The 

 mirror is placed in front of the lens so that the plane of the 

 ni'rror makes an angle of about 33^ with the axis of the 

 lens. The mirror extinguishes the polarised light, and so 

 causes the image of the cloud to stand out brightly on a 

 dark background. Mr. Birt Acres contributes some fine 

 specimens of cloud photography, as also do Dr. F. G. 

 Smart, Dr. A.' Sprung, Colonel H. M. Saunders, and 

 Captain D. Wilson-Barker. 



Some interestmg photographs of several remarkable 

 clouds are exhibited. Two of these show the "festooned 

 cumulus " (or pocky cloud) that formed part of a storm- 

 cloud which passed over Sydney, New South Wales, on 

 January 18, 1893. Mr. H. C. Russell, F.R. S., exhibits 

 two photographs illustrating the "southerly burster" 

 (which is a violent inrush of Polar wind) at Sydney on 

 November 13, 1893. The first was taken at 6 p.m., and 

 shows the clouds preceding the "burster." In the 

 second, which was taken an hour later, the "roll cloud" 

 had come near enough for its peculiar character to be 

 distinctly seen, and the evident rolling up of the cloud is 

 very well shown, as well as the light rain squall which 

 sometimes accompanies these winds. Three photographs 

 of tornado clouds are exhibited, in two of which the 

 cloud funnel was twelve miles distant, and in the third 

 the spiral-shaped funnel is seen trailing at a considerable 

 altitude in the air. 



A collection of pictorial illustrations of clouds, from 

 various meteorological works, is also set out in the exhi- 

 bition. The earliest of these is a plate showing the 

 method of measuring the height of clouds, by means of 

 two theodolites, from J. F. Glockner's De Pondere 

 Nubiiim, 1722. 



The instruments used for observing the direction of 

 motion of the clouds are called "nephoscopes " ; and of 

 these there are several specimens in the exhibition, 

 amongst them being those devised by Mr. Goddard, Herr 

 Fineman, General R. Strachey, F.R.S., and Mr. F. 

 Galton, F.R.S. These consist of circular mirrors with 

 radial or parallel lines marked on them, the points of the 

 compass being engraved on the outside of the frames. 

 The direction of motion of a cloud is ascertained by 

 turning the mirror on its axis until the image of the cloud 

 passes along one of the lines. Photo-nephographs, de- 

 signed by Captain Abney, F.R.S. , and by MM. Teisserenc 

 de Bort and G. Raymond, are also exhibited ; as well as 

 a model showing the manner in which the pair of photo- 

 nephographs are mounted for use at the Kew Observ- 

 atory, and the apparatus designed by the late Mr. G. M. 

 Whipple for ascertaining the height, direction, and rate 

 of motion of clouds from the photographs. In this case 

 simultaneous photographs of a cloud are taken by two 

 cameras half a mile apart, and fixed in such a way 

 that their optical axes point to the zenith. The 

 dark slides of the cameras carry a pair of fiducial 

 lines at right angles to each other, and adjusted 

 so that one of the lines shall be parallel to 

 the measured base, and these lines are repro- 

 duced upon the cloud photographs. The two 

 negatives are super-imposed in the sliding frames of 

 the apparatus, which are then moved till the images of 

 the cloud exactly coincide, when the parallax is given by 

 a line joniing the intersections of the fiducial lines. The 

 parallax having been measured by a pair of compasses, 

 the height of the cloud is at once determined by means 

 of a prepared curve. A similar operation is then per- 

 formed with one of the same negatives, and a second 

 taken in the same camera after the lapse of one or more 

 minutes. The pictures having been made to coincide as 

 before, the distance between the intersections of the fidu- 

 cial Hnes indicates the drift of the cloud. The direction 



NO. 1277, VOL. 49] 



of the drift is indicated by the position of the line joining 

 the two intersections relatively to the fiducial line parallel 

 to the base. The velocity of the drift, or the rate of 

 motion of the cloud, is found graphically by means of a 

 prepared diagram. Mr. R. Inwards exhibits a simple ap- 

 pliance for estimating the height of clouds of the roll- 

 cumulus type by means of their perspective effect. 



The exhibition includes a number of instruments in- 

 vented or first constructed since the previous exhibition. 

 Mr. R. W. Munro shows a very fine specimen of Dines' 

 recording pressure-tube anemometer, as well as two other 

 patterns of Dines' pressure and velocity gauge for use 

 with the tube anemometer. Mr. J. J. Hicks exhibits 

 Bartrum's open scale barometer, Callendar's compen- 

 sating open scale barometer, Keatmg's hydrometer, and 

 some useful and pretty circular levels with the fluid her- 

 metically sealed. Mr. L. P. Casella shows Goad's geo- 

 detic altazimuth, a universal sun-dial, some artificial 

 horizons, an alarm thermometer by MM. Richard 

 Freres, and a hypsometer or boiling-point thermo- 

 meter. Mr. H. Hainsby, a shoemaker at Shanklin, 

 exhibits three ingenious instruments which he has him- 

 self devised and constructed. These are an inverted 

 tube-hygrometer, a vapour condenser, and a compen- 

 sating siphon evaporator for large water surfaces. Mr. 

 H.N. Dickson shows a model of his bottle for collecting 

 samples of sea water from moderate depths, and Dr. W. 

 G. Black shows his louvered glass evaporator. 



A number of sketches and photographs of meteoro- 

 logical phenomena are also exhibited, as well as photo- 

 graphs and diagrams of instruments. 



A special feature of the exhibition is the large and 

 interesting collection of lantern slides, nearly 300 in 

 number, and mostly of cloud subjects. 



Wm. Marriott. 



NOTES. 



The next meeting of the American Association for the Ad- 

 vancement of Science will be held in August, at Brooklyn. 

 The mayor of that city has just appointed alar^e and influential 

 local committee to make arrangements for the meeting. 



The fine weather of the past few weeks has enabled General 

 Pitt-Rivers, F.R.S., to resume his excavations at Wor-Brrrow, a 

 large twin-barrow near Woodyates, on the bDrders of D jrset and 

 Wilts. An extensive section has been cut through the tumulu s, 

 and quite recently the work of the investigator was rewarded by 

 the discovery on the old surjace line of two human skeletons. 

 Anthropologists will await with interest the results which may be 

 deduced from the examination and measurement of these re- 

 mains, and their relation to those already made by General 

 Pitt-Rivers in the round barrows, and in the RammoBntish 

 settlements explored in the immediate neighbourhood. 



The Royal Commissioners appointed "to inquire and report 

 what light-houses and light-vessels it is desirable to connect 

 with the telegraphic system of the United Kingdom by electrical 

 communication, for the purpose of giving information of vessels 

 in distress or casualties at sea to places from which assistance 

 could be sent, and of transmitting storm warnings," have pre- 

 sented their second report. Although the general question of 

 signalling was not referred to the Commissioners, it is so 

 intimately connected with the subject of electrical communica- 

 tion that they have considered it, and in the first report they 

 stated that in cases " where the distance from the shore is not 

 great, an improved system of distress-signals (distinct from the 

 usual fog-signals) might, both at rock-stations and on light- 

 vessels, prove an effective temporary substitute for the more 

 costly expedient of electrical communication." This view has 



