February io, 1910] 



NA TURE 



427 



LETTERS TO THE EDITOR. 



ITIie Editor docs not hold himself responsible for opinions 

 expressed by his correspondents. Neither can he undertake 

 to return, or to correspond zvith the writers of, rejected 

 manuscripts intended for tliis or any other part o/ Nature. 

 No notice is taken of anonymous communications.] 



Surface Deformation and the Tides. 



Four years agj I installed in a cellar beneath the 

 Victoria Club, at Ryde, an astronomical level. It was 

 oriented at right angles to the shore-line, only a few yards 

 distant. At the time of high water I found, contrary to 

 my expectation, that the strand, rather than sink- 

 ing, rose upwards. This I attributed to the tide backing 

 up underground drainage beneath the land, which in con- 

 sequence bulged upwards. Sir George Darwin, however, 

 makes the suggestion that my observations might be ex- 

 plained on the assumption that the load of water in the 

 English Channel on tine south of the Isle of Wight might 

 reverse the effect of a smaller body of water in the Solent 

 on the north side. 



I was enabled to mafcei a 'Second attempt to measure the 



the steepness of the bounding shores is increased. The 

 buildings in towns along sea-boards twice a day are tilted 

 seawards. When the tide flows out these movements are 

 reversed. The deflection of the pendulum by tidal load and 

 attraction, although greater than might be expected, is, 

 however, very small. At Bidston it is about 02", or i inch 

 in sixteen miles. John Milne. 



Shide, Isle of Wight, January 24. 



A Possible Identification of Comet igogt-. 



Herr Ebell has recently determined approximate elliptic 

 elements for this comet. 



These elements bear some resemblance to those of 

 comet 1890 VII. Spitaler, which has a period of 6-373 +001 

 years, and has not been seen again. 



Comet Spitaler had a perihelion distance of i-8 and an 

 aphelion distance of j-i. It passes near no other planets 

 than Mars and Jupiter. The small mass of Mars makes 

 the perturbations by that planet of little account. 



As comet Spitaler's period is half that of Jupiter, it only 

 approaches Jupiter at alternate aphelion passages. It did 



changing slope along a coast in consequence of tidal in- 

 fluences through the kind cooperation of Mr. W. E. 

 Plummer, the director of the Bidston Observatory. This 

 observatory is situated near Birkenhead, about one and a 

 half miles from the sea. The instrument is a slightly 

 modified form of a British Association type of seismograph. 

 It consists of a horizontal boom, 2 feet in length, carrying 

 a weight of 6 lb. At the outer end of the boom there is 

 an extremely light lever, which multiplies the movement 

 of the boom eight times. This, which is a peculiar feature 

 of the apparatus, was designed by my assistant, Mr. 

 Shinobu Hirota. The outer end of this pointer moves 

 above a surface of bromide paper driven by clockwork. 

 A displacement of the image shown on the paper through 

 a distance of i mm. corresponds to the displacement which 

 would be obtained were the stand of the pendulum tilted 

 through an angle of o-o8". The objects of this installation 

 are two-fold, first, to record tidal effects, and, secondly, 

 to pick up minute movements which other types of seismo- 

 graph seldom record. The accompanying figure shows the 

 tidal effect, which varies with the height of the water, the 

 ebb, and the flow. 

 At high tide the bed of the Irish Sea is depressed, and 

 NO. 2102, VOL. 82] 



not approach Jupiter at its aphelion after its appearance in 

 1890, but it did approach Jupiter on the following aphelion 

 passage, 1899-1900. 



The comet's motion is direct, and it therefore remains 

 in proximity to Jupiter for a considerable time. Its closest 

 approach took place about 1899 November 8, when its 

 distance was about 06 and its eccentric anomaly 160°. 

 For more than a year it remained within a distance 08 

 of Jupiter, and the perturbations must have been consider- 

 able. If we carry Ebell 's orbit backwards, we see that 

 comet igoge was also near Jupiter in i8gg-igoo, and there 

 is, therefore, a fair probability of the two comets being the 

 same. 



If Ebell's elements were definitive, this identification 

 would have to be given up, for a rough calculation shows 

 that the changes of elements are not in the right direction 

 or of the right magnitude. Ebell's elements, however, 

 merely represent the first attempt to get elliptic elements 

 instead of parabolic elements. They depend on three places 

 only, the first and last being six weeks apart. Herr Ebell 

 himself tells us that the residuals for a fourth observation 

 in the middle of the above-mentioned six weeks amount to 

 a minute of arc, so that it is quite conceivable that the 



