218 



KNOWLEDGE 



[November 2, 1891. 



volume of water, cut its way through the beds which 

 surrounded it, and, deriving large quantities of flints 

 from the existing Eocene pebble beds, it proceeded to 

 scatter them along its banks, and to deposit them in the 

 then lower reaches of the river, thus giving rise to those 

 wide tracts of "gravel and sand" (2) which cover so 

 large an area in South Loudon. These gravel deposits 

 must not be confounded with certain gi-avel beaches and 

 terraces which occur in the north of London and which 

 owe their origin to the glacial conditions already referred 

 to as also giving rise to the boulder clays. 



In approaching London from the east, as soon as we get 

 clear of a line drawn from Greenwich through Lewisham, 

 and extended southward, we leave all the outcrops of the 

 London tertiaries behind, with the exception of one, viz., 

 the London Clay. This important formation, together with, 

 in some parts, the river gravels, constitute almost the 

 whole of South London between the imaginary line we 

 have drawn, and a western boundary which we may fix as 

 far west as Kingston and AVimbledon. The eastern part of 

 Wimbledon Common is London Clay, and on the west the 

 gravels are well developed. Tooting Common is situated 

 on the clay. North Brixton and Clapham are mostly built 

 upon gravel, although in the latter place the clay shows 

 itself largely at Clapham Park. Sydenham, the Crystal 

 Palace, and Forest Hill are built upon clay, but both north 

 and south of the Palace there are two patches of gravel on 

 the summit of the hills. Think of the time when the 

 river was sufliciently broad to deposit this gravel, about six 

 miles from the present river ! Continuing eastward, we 

 find a thick bed of gravel following the valley of the Siver 

 Eavensbourne, identical in direction with the Lewisham 

 Road, and reaching to the south of Bromley. 



North of these jjlaees, and between them and the river, 

 the surface consists of " gravel and sand," except of course 

 in the immediate \icinity of the river. This would seem 

 to show that the river, previous to laying down the gravel, 

 destroyed a great part of the tertiaries, leaving only a part 

 of the London Clay exposed, and then with the denuded 

 fragments deposited the pebbles in the form of gravel. 



Thus the work of destruction arjd denudation went on 

 side by side with that of construction, the two actions to 

 some extent counterbalancing one another. 



It is a strikmg fact that the next formation — that of the 

 Alluvium (1) — although found to so great an extent below 

 London Bridge, is scarcely found at all above it, and this 

 is, indeed, very likely to have been the cause of the choice 

 of site on which the city was built. Over a large part of 

 Bermondsey there appears this thick bed of river mud, 

 whilst in the bed of the river, eastward fi'om London Bridge, 

 an important fault appears to have occurred, so that the 

 strata on the north of the river have sunk down to a lower 

 level than those on the south. The result of this fault was 

 that the river spread itself over a wide tract of land on the 

 north, and in prehistoric times deposited alluvium wherever 

 it went. Even now the level is considerably lower than 

 that on the south, and consists principally of wide stretches 

 of marsh land. 



THE FACE OF THE SKY FOR NOVEMBER. 



By Herbert Sadler, F.E.A.S. 



THERE is no diminution in the increase of the number 

 of solar spots and faculre. The following are con- 

 veniently observable minima of some Algol-type 

 variables {rf. "Face of tlie Sky" for October). 

 U Cephei. — November 2nd, Oh. 11m. a.m. ; Novem- 

 ber 6th, llh. 60m. p.m. ; November 11th, llh. 30m. p.m. ; 



November 16th, llh. 10m. p.m. ; November 21st, lOh. 

 50m. P.M. ; November 26th, lOh. 29m. p.m. Algol. — 

 November 2nd, llh. 30m. p.m. ; November .^th, 8h. 9m. 

 P.M. ; November 8th, 5h. 7m. p.m. ; November 2.5th, 

 lOh. Im. p.M ; November 28th, 6h. 49m. p.m. X Tauri.— 

 November 2nd, midnight ; November 0th, lOh. 53m. p.m. ; 

 November 10th, 9h. 45ra. p.m. ; November 14th, 8h. 37m. 

 P.M. ; November 18th, 7h. 29m. p.m. ; November 22nd, 

 6h. 23m. P.M. ; November 26th, 5h. 15m. p.m. 



With the exception of Jupiter and Neptune, none of the 

 planets are well situated for observation by the amateur in 

 November. Mercury is practically invisible as, though he 

 sets on the last day of the month at 4h. 40m. p.m., or 46 

 minutes after the Sun, his tremendous southern declina- 

 tion (25f°) will preclude observation. The same may be 

 said of Venus, setting as slie does on the 30th at 41i. 55m. 

 P.M., or Ih. Im. after the Sun, with a southern declination 

 of 24° 19'. Mars does not rise on the last day of the 

 month till 3h. 39m. a.m , and Saturn not till Ih. 6m. a.m. 

 Jupiter is stOl a magnificent object in the evening sky, 

 setting on the 1st at Ih. 15m. a.m., with a southern declination 

 of 9^ 48', and an apparent equatorial diameter of 44^". 

 On the last day of the month he sets at llh. 26m. p.m., 

 with a southern declination of 9° 15', and an apparent 

 equatorial diameter of 40J". The phasis on the preceding 

 limb of the planet is now very perceptible, amounting at 

 the end of the month to /j; of a second of arc. The fol- 

 lowing phenomena of the satellites occur before midnight, 

 whUe Jupiter is more than 8^ above, and the Sun 8° below, 

 the horizon. On the 1st, an eclipse reappearance of the 

 first satellite at 7h. 37m. 53s. On the 2nd an occultation 

 disappearance of the second satellite at 7h. 39m. p.m. 

 On the 3rd an eclipse reappearance of the third satellite at 

 5h. 27m. 25s. p.m. On the 4th, a transit egress of the 

 second satellite at 5h. 38m. p.m., and of its shadow at 

 8h. 2m. P.M. On the 6th, a transit ingress of the third 

 satellite at llh. 10m. p.m., and an occultation disappear- 

 ance of the first satellite at llh. 34m. p.m. On the 7th, a 

 transit ingress of the first satellite at 8h. 42m. p.m., of its 

 shadow at 9h. 57m. p.m., and a transit egress of the satellite 

 at llh. Im. P.M. On the 8th, an occultation disappearance 

 of the first satellite at 6h. 2m. p.m., and an eclipse reap- 

 pearance of the satellite at 9h. 33m. 32s. p.m. A transit 

 egress of the first satellite at 5h. 29m. p.m. on the 9th ; a 

 transit egress of its shadow at 6h. 44m. p.m. ; a transit 

 ingress of the shadow of the fourth satellite at 7h. 27m. 

 P.M. ; an occultation disappearance of the second satellite 

 at lOh. 7m. p.m. ; a transit egress of the shadow of the 

 fourth satellite at llh. 6m. p.m. On the 10th, an eclipse 

 disappearance of the third satellite at 6h. 21m. 17s. p.m., 

 and a reappearance at 9h. 28m. 55s. p.m. On the 11th, a 

 transit ingress of the second satellite at 5h. 15m. p.m., a 

 transit ingress. of its shadow at 7h. 50m. p.m.; a transit 

 egress of the satellite at 8h. 8m. p.m., and of its shadow at 

 lOh. 40m. P.M. On the 14th, a transit ingress of the first 

 satellite at lOh. 34m. p.m. On the 15th, an occultation 

 disappearance of the first satellite at 7h. 55m. p.m. On 

 the 16th, a transit ingress of the first satellite at 5h. 3m. 

 P.M., of its shadow at 6h. 22m. p.m. ; a transit egress of 

 the satellite at 7h. 21m. p.m., and of its shadow at 8h. 40m. 

 P.M. On the I7th, an eclipse reappearance of the first 

 satellite at 5h. 58m. 3s. p.m. ; an occultation reappearance 

 of the first satellite at 6h. 23m. p.m. ; an occidtation reap- 

 pearance of the third satellite at 8h. 21m. p.m. ; an echpse 

 disappearance of the third satellite at lOh. 23m. 32s. On 

 the 18th, a transit ingress of the second satellite at 7h. 47m. 

 p.m., of its shadow at lOh. 28m. p.m. ; and a transit egress 

 of the satellite at lOh. 41m. p.m. On the 20th, an echpse 

 reappearance of the second satellite at 7h. 23m. 26s. p.m. 



