SCIENCE-GOSSIP. 



These two rivers, but perhaps more especially 

 the latter, are at times very muddy in their courses, 

 especially when the water is flowing a little quicker 

 than usual. The material which causes this is 

 principally derived from one or other locality on 

 the river banks, and is deposited further up or 

 down the river, as the case may be, according to 

 the tide. In this manner the mud is continually 

 moving from one spot to another, though in the 

 aggregate the result is very trifling, and no great 

 amount reaches the Humber waters. The 

 sediment that does reach the Humber • by the 

 rivers can only be a very small proportion of that 

 which exists in the estuary ; and as it apparently 

 does not come down the rivers flowing into the 

 Humber, it must come in from the sea. In order 

 to ascertain whether this is likely or not, it must 

 be ascertained what is going on outside the river. 



The waters of the North Sea are continually 

 washing particles of rock, sand and mud in a 

 southerly direction, and slowly but surely the 

 material on the Yorkshire coast is travelling south- 

 ward. It never travels in a northerly direction. 

 A good illustration of this can be found in the 

 chalk boulders around Flamborough headland. As 

 is well known, the beach around that promontory is 

 strewn with masses of chalk of all sizes which have 

 been dislodged from the cliffs. These can be seen 

 in plenty in Bridlington Bay and further south, 

 though naturally getting less plentiful as they 

 get towards the Humber. Practically no chalk 

 boulders are to be found north of the headland. 

 This goes to prove conclusively, if proof be 

 needed, that the beach material travels to the 

 southward. 



The cliffs of the Holderness coast are made up 

 entirely of soft glacial clays, capped in one or two 

 places by lacustrine deposits of small extent. They 

 vary in height from ten feet to fifty feet, and at 

 Dimlington reach over one hundred feet. Mr. 

 J. R. Boyle, F.S.A., has shown* on historical 

 evidence, and the Rev. E. M. Cole and others have 

 proved by direct observation,! that the whole of 

 the cliffs from Bridlington to Spurn are being 

 eroded at an average rate of about seven feet per 

 annum. A walk along the cliffs at any point, 

 especially in the spring time, will convince the 

 observer that this estimate must be fairly accurate, 

 or at any rate not under-estimated. As, therefore, 

 the boulder-clay cliffs, varying in height from ten 

 feet to over one hundred feet, are being washed 

 away at seven feet per annum, the whole of that 

 material must be gradually, or, as it is in some 

 cases, quickly converted into gravel, sand or mud, 

 and carried southwards. 



* - 'The Erosion of the Holderness Coast." — Trans. Hull 

 Geol. Soc, 1895-6, vol. iii., pp. 16-17. 



f" Erosion of the Yorkshire Coast," 1892. — "Naturalist," 

 1893, pp. 142-144. 



It is generally admitted that a large quantity of 

 the material is carried past the Humber mouth 

 and is gradually silting up in the Wash and off the 

 Lincolnshire coast, but at the same time a deal of 

 the material must be brought into the Humber at 

 each tide ; and when the winds are the strongest, 

 and the rate of erosion is consequently the most 

 severe, the inrush of water into the Humber is 

 likewise the greatest. This water brings with it 

 the cliffs in a modified form. It would appear, 

 therefore, that it is from the coast that the bulk of 

 the material in suspension in the Humber waters is 

 derived. Of course, it does not follow that the mud 

 now in the Humber is the result of one or two 

 tides. The particles in the water may have been 

 accumulating during several months, and undoubt- 

 edly pass and re-pass a particular point several 

 times a week. Consequently, when the rivers 

 flowing into the Humber are swollen with flood 

 waters, and are swift, the muddiness observed near 

 the entrances to the estuary is not necessarily due 

 entirely to the additional material which they have 

 brought down, but is more likely to be owing to 

 the sediment in the Humber being stirred up. 

 About four years ago, during an exceptionally dry 

 summer, the Humber water was, comparatively 

 speaking, in a clear condition. This was not 

 altogether due to the lack of material brought 

 down by the rivers on account of their almost dry 

 condition ; rather may we attribute it to the fact 

 that the mud was not stirred up to any extent, 

 but was brought in by the Humber, deposited at 

 high water, and left. 



The work being done by geologists in connection 

 with the deposits at the mouths of other rivers, 

 suggests that a microscopic examination of the 

 particles in the Humber water would probably 

 enable it to be ascertained definitely whether the 

 bulk of the material came from the cliffs of Holder- 

 ness, or from the rivers Ouse, Trent and Hull. 

 Unfortunately this cannot be carried out satis- 

 factorily in the case of the Humber estuary, as 

 particles of a precisely similar nature to those 

 brought down by the rivers are also to be found in 

 the cliffs of the east coast. Of course very fine 

 mud, such as would be derived from clays, etc., 

 can be of little assistance in the. matter, but the 

 sand grains and the particles of the uncommon 

 minerals found amongst them are more likely to 

 throw light on the question. 



It must be borne in mind that the erosive action 

 of the rivers is the greatest where the ground is the 

 highest and the gradient the steepest, viz., at their 

 sources. It is here that the current is the swiftest 

 and consequently the rocks and soil on either side 

 of and in the bed of the streams are dislodged and 

 carried away. Very little erosion is going on near 

 the mouths of the rivers. It naturally follows, 

 therefore, that such particles as are brought down 



