Feb. 8, 1872] 



NATURE 



285 



night. The aurora was probably extensive, as the evening, not- 

 withstanding the clouds, was nearly as bright as moonlight. 

 Guildford, Feb. 5 T. Rand Capron 



The Floods 



Two of the largest districts which are most constantly flooded 

 are, perhaps, Oxford and " The Plain of York. " The same 

 cause floods both these districts, namely, what Mr. Mackinto'sh 

 has called " Colonel Greenwood's hard gorge and soft valley 

 theory." Both these districts have been worn down by rain and 

 rivers in the soft oolitic strata ; and the Humber and the Thames 

 have ever had, and have now, to force outlets through compara- 

 tively hard chalk gorges. The rain-flood waters, checked at 

 these gorges, overflows and deposits alluvium behind the gorges. 

 The same takes place in the soft strata of the Weald, behind the 

 nine comparatively hard chalk gorges of the North and South 

 Downs. GfiOKGE Greenwood 



Brookwood Park, Alresford, Feb. 3 



Zodiacal Light 



The evening of Feb. 2 being clear, after a long persistence of 

 rainy cloud for many days, about 6.5 P.M.I began to notice the 

 existence of a zodiacal light. Some time later, probably aliout 

 6.40, it was considerably brighter than any portion of the gilaxy 

 in sight at the time, though this might not have been the im- 

 pression of an inattentive spectator, as the gradual melting away 

 of its edges produced much le.ss cont-ast with the ground of the 

 sky than the better defined outline of the Milky Way. Its light 

 was, in fact, so imperceptibly dilTused that it was impossible to 

 fix is boundaries or extent with any accuracy. Its general 

 position was, however, undoubtedly a 1 ttle below the square of 

 Pegasus (where its upper edge fell short of a an"! 7), and beneath 

 the three stars of Aries ; but its light was here so enfeebled th ;t 

 its termination was quite uncertain, and it could only be said that 

 the direction of its axis was towards the Pleiades. Its breadth 

 where most brilliant, near Pegasus, might probably be estimated 

 at 8° or 9°, fr^m comparison with the distance from a. to /8, and 

 with the length of the belt of Orion ; but this determination was 

 liable to great uncertainty. It was thought to show a ruddy 

 tinge, not unlike the commencement of a crimson Aurora Borea- 

 lis ; this may have been a deception, but it was certainly redder 

 or yellower than the galaxy. At 7 I examined it with a little 

 pocket spectroscope, which shows very distinctly the greeni>h 

 band of the aurora ; but nothing of the kind w.as visible, nor 

 could anything be traced beyond a slight increase of general 

 light, which, in closing the slit, was extinguished long before 

 the auroral band would have become impercep'ible. It was 

 still visible at S. 30. The phenomenon had b=en previously 

 noticed, but with less distinctness, on Dec, 30 and Jan. ii, 



T. W. Wedb 



Hardwick Vicarage, Herefordshue 



Magnetic Disturbance during Solar Eclipse 



With the knovm relation existing between the sun and terres- 

 trial magnetic disturbance, it is not surprising that some indica- 

 tion of a change in the earth's magnetism might be expected 

 during a solar eclipse ; and the case cited by the Rev. S. J. 

 Perry, of its supposed observation by M, Lion, is not the first 

 instance of the kind. 



Shortly after the eclipse of 1870, Signor Diamil'a Miiller, of 

 Florence, published a paper in the Gazzetta Ufficiale, No. 17, 

 describing some magnetic observations made in Italy during the 

 2 1st, 22nd, and 23rd December, and from which it appeared 

 that there was a slight variation in the curve of the 22nd, at the 

 time of the eclipse, which did not appear in the curves of the 

 preceding and subsequent days. Signor Miiller at once con- 

 cluded that the variation was produced by the eclipse ; but it 

 was pointed out by Senhor Capello, of the Lisbon Observatory, 

 that the same disturbance was recorded by his self recording 

 instruments, but it occurred there some time before the totality. 

 It was also recorded by the instrviments here, and proved to be 

 insignificant when compared with other disturbances continually 

 observed, 



A careful examination of the curves for the time of the i860 

 eclipse has also failed to show any trace of a siicilar movement 

 then occurring. G, Mathus Whippi.e 



Kew Observatory, Feb 5 



Circumpolar Lands 



Mr. Hamilton, in Nature-oI January 25, refers to a paper 

 in which " the rising of the land at the poles is inferred as a ne. 

 cessary result of the cooling and contracting of the earth." He 

 then goes on to give the substance of part of the paper, beginning 

 as follows : — 



" If a spheroid of equilibrium, in motion about an axis, con- 

 tract uniformly in the direction of lines pei-pendicular to its sur- 

 face, a new spheroid is produced, having a greater degree of 

 eccentricity, because if equal poitions are taken off the two 

 diameters, the ratio of the equatorial diameter is increased. This 

 is equivalent to a heaping up of matter around the equator." 



Th- reasoning of this latter passage appears sound, but it con- 

 tradicts the former one. As I have shown in my letter to which 

 Mr. Hamilton replies, the facts, so far as known, appear to point 

 to a relative increa'*e of the polar diameter ; he admits this, and 

 then gives reasons for expecting a relative increase of the equa- 

 torial one. He must have made some oversight. 



Old Forge, Dunmurry, Jan. 27 Joseph John Murphy 



THE HISTORY OF PHOTOGRAPHY 

 T TRUST you will kindly allow me space for a few lines 

 ■'■ on the subject of some rare specimens connected 

 with the History of Photography, now in the possession 

 of Madame Nifepce de St. Victor, whose husband it will 

 be remembered v/as the first to employ glass, and a trans- 

 parrnt medium (albumen) for the purposes of photo- 

 graphy, thus discovering, to a great extent, the process 

 of Photography as it exists at the present day. The first 

 glass negative, or rather i://c/i(', Madame Niepce possesses, 

 as likewise prints executed in 1848, 



Niepce de St. Victor was likewise one of those who 

 have worked hard to secure natural colours in the camera, 

 some very perfect specimens — photographs of coloured 

 dolls — which prove distinctly that the solution of the 

 problem is not impossible, as many believe, are also in- 

 cluded in the Nicpce collection, together with some results 

 of early photo-engraving. 



Madame Niepce and family have been left, I regret 

 to say, in very straitened circumstances, for the busy 

 philosopher in his lifetmie had but the pay of a subordi- 

 nate officer in the French Army to subsist on. She has 

 placed in the possession of the Photographic Society this 

 valuable collection of her late husband, and it is proposed 

 to exhibit it at the next meeting of the Society on the 13th 

 inst,, and any institution or individual desiring to become 

 possessed of some of the specimens wiU be readily fur- 

 nished with information by H. Baden Pritchard 



GANOT'S PHYSICS' 



GANOT'S Physics is so well known in this country 

 that our task is very different from that of reviewing 

 a new work, and we can do little more than compare this 

 edition with the previous. It is unusual for any large 

 scientific work to pass through five editions in about ten 

 years, and the value of the book may be estimated by 

 this fact. It has passed through more than twice the 

 above number of editions in France, and has been trans- 

 lated into various European languages. In the present 

 edition the type has been altered, and the size of the page 

 somewhat increased, while twenty-eight new illustrations 

 have been added, and the te.xt has been augmented. 



The doctrine of energy has of late been so largely 

 developed that we are surprised to find so small an 

 amount of space given to the subject. No more than 

 two pages are devoted to it, while the term " transmuta- 

 tion of energy," does not appear in the index. Neither 

 do we find the terms " Kinetics " and " Kinematics ; " yet 

 we imagine that the student who presented himself as a 

 candidate for a Science Scholarship at any of our Uni- 



* An Elementary Treatise on Physics, Experimental and Applied. Tran- 

 slated and Edited from Ganol's " Elements de Physique," by E. Atkinson, 

 Ph.D., F.C S. Fifth Edition, Revised and Enlarged. 828 pp. 8vo. (Loa, 

 don: Longmans and Co. 1&72.)' 



