May n, 1 882 J 



NATURE 



about a hundred miles to the southward, it was often 

 necessary to depend more on the density of the water, on 

 account of the subsidence of the sediment. 



Without entering into the details it may be sufficent to 

 state that, whilst the waters of the Yang-tse, according to 

 my observations, became permanently free from sedi- 

 ment, and assumed the more marked characters of sea- 

 water, with a minimum density of roiS, at a distance of 

 about forty miles east of Wusung, they still retained their 

 yellow colour and turbid appearance, with a density vary- 

 ing between 1005 and i - oii, on the outskirts of the 

 Chusan archipelago, about a hundred miles to the south- 

 ward. From these data the conclusion may very naturally 

 be drawn that the main body of the water discharged by 

 the Yang-tse flows comparatively undisturbed in a southerly 

 direction across the Hang-chu Bay to the Chusan archi- 

 pelago. The southerly extension of the muddy waters of 

 the Yang-tse in the neighbourhood of Chusan 1 must have 

 been a frequent subject of remark to any one approaching 

 Shanghai from the southward, and should he at some 

 subsequent period undertake the voyage from that port to 

 Nagasaki, he will be very probably surprised to find him- 

 self, some four or five hours after leaving Wusung, sur- 

 rounded by the green waters of the Eastern Sea. The 

 situation of the Great Yang-tse bank, which extends one 

 hundred and fifty miles to the north-east from the mouth 

 of the river, would appear to negative the conclusion at 

 which I have arrived ; but I am inclined to view this 

 bank — lying as it does rather off the entrances to the 

 river, and composed as it is of fine grey sand — as rather 

 the work of a past period, when perhaps the bulk of the 

 waters found a passage to the north of the island of 

 Tsung-ming, than as being in actual formation at present. 

 That a vast amount of sediment is deposited to the south- 

 ward of the estuary at the present time we have the most 

 undoubted testimony in the rapid shoaling of the sea 

 amongst the islands of the Chusan archipelago, and 

 along the shores of the Hang-chu Bay, which has caused 

 channels at one time navigable for junks to be ;.ow 

 impassable. 



With reference to the general effect of the water dis- 

 charged by the Chinese rivers on the density of the 

 Yellow Sea and of the Gulf of Pe-chili, I may observe 

 that in the month of October I found the specific gravity 

 to rise slowly from 1019 at the base of the Great Yang- tse 

 bank — a point between fifty and sixty miles east of 

 Wusung — to 1023 amongst the islands of the Corean 

 archipelago ; and that the maximum of 1 024 was attained 

 at a point mid-way between this archipelago and the 

 Shantung promontary. North of this cape the density 

 does not vary in any marked degree, but after the Miau- 

 tau Islands were passed — a group which separates the 

 Gulf of Pe-chili from the Yellow Sea — there was a 

 gradual diminution, until, at our nearest point of approach 

 to the Yellow River, the mouth of which was forty- five 

 miles distant, the specific gravity was ro2I. This slight 

 fall in the density was the only indication of our proximity 

 to such a large river as the Hoang-ho — a circumstance 

 which has a particular bearing on the excessive amount of 

 sediment which this river has been estimated to discharge 

 (vide Nature, vol. xxii. p. 487). From this point to the 

 mouth of the Pei-ho the specific gravity continued to de- 

 crease, until at a point about twenty-three miles from the 

 mouth of this river, where the discolouration from sedi- 

 ment was first observed, it was ro20. Thence to the 

 Taku forts the density rapidly fell. 



We may thus place the specific gravity of the Gulf of 

 Pe-chili at from 1 '020 to 1 023, and that of the Yellow 

 Sea at from ro22 to ro24, whilst the difference between 

 these densities and that of oceanic water — ro27 — will 

 represent the combined effect of the discharge of the 



1 I may take this opportunity of observing, that on one occasion whenoff 

 the northern extremity of Chusan, I noticed several large medusae floating 

 on the surface of the water, which was not only muddy in appearance but 

 had a density of i *oo6. 



Pei-ho, the Yellow River, and to a less degree of the 

 Yang-tse, on the specific gravities of the seas in question. 



I must conclude with an observation on the erroneous 

 notion which the appellation of "Yellow Sea" must con- 

 vey to the minds of most men. For however much the 

 Yellow Sea may have merited the epithet of " yellow ' ' 

 when it received the waters of the Hoang-ho about a 

 quarter of a century ago — though if an inference is to be 

 drawn from the present condition of the Gulf of Pe-chili 

 it could scarcely have been entitled to it even at that 

 period — it has no claim whatever to it now. Free from 

 sediment and dark green in colour, except in the imme- 

 diate vicinity of the estuary of the Yang-tse, the Yellow 

 Sea has been more appropriately named by Chinese 

 sailors— "The Black-water Ocean." H. B. Guppy 



H.M.S. Lark, Sydney 



PROFESSOR GEIKIE IN ARRAX 



AMONG the many features which have lent attraction 

 to the study of geology at F.dinburgh University, 

 Prof. Geikie's field demonstrations have always held a 

 conspicuous place. Few favourable Saturdays have been 

 allowed to pass, on which he might not be seen rambling 

 with his class through some wooded glen, or climbing 

 some rugged brae, with hammer, sketch-book, and map- 

 case, and every now and then stopping to point out some 

 striking rock section, or to examine a " find," made per- 

 chance by one of his students. But at the end of the 

 session, when a week or ten days are devoted to the ex- 

 ploration of some district possessing an interesting geo- 

 logical structure, the " long excursion" is always looked 

 forward to with the keenest delight by professor as well 

 as by students. The first long class-excursion ten years 

 ago was to Arran, and the Professor decided that his last 

 should also be to that island — famous alike for the beauty 

 of its scenery and for the interest attaching to its geo- 

 logical framework. Quarters were taken up at Corrie 

 Hotel on Monday April 24, and that afternoon saw the 

 whole party, numbering about a score, roaming with bags 

 and hammers along the coast towards North Glen Sannox, 

 and making the acquaintance of the coarse red sand- 

 stones and brecciated white quartz conglomerates of the 

 Upper Old Red, or Lower Calciferous Sandstone series, 

 which extend in a broad belt round that part of the 

 island. Further inland, a coarse conglomerate made up 

 of well-rounded pebbles of pinkish quartz interstratified 

 with characteristic dark chocolate-coloured sandstones 

 and occasional argillaceous beds, was ascertained some 

 years ago by the Professor to belong to the Lower Old 

 Red Sandstone, and to be brought down by a fault 

 against the schists that fringe the mountainous granitic 

 core of the northern half of the island. He had already 

 made some progress with a geological map of the island 

 on a scale of six inches to a mile, and he now purposes to 

 continue this work with the co-operation of his students. 

 Resuming his geological boundary-lines at Glen Sannox, 

 the party was soon scouring the hillsides far and near, in 

 search of rock-sections and exposures, while he, map in 

 hand, remained within ear-shot, and superintended opera- 

 tions, marking down the lines of junction, and unravelling 

 the geological structures with the skilful hand of one 

 long acquainted with the art of geological mapping. In 

 this way several miles of the boundary between the 

 granite and schists were mapped. In the course of a 

 walk along the steep craggy Suidhe Fearghus, on the 

 north side of Glen Sannox, the trend of this remarkable 

 ridge was found to coincide with that of the vertical joint 

 in the granite, and the deep gashes which indent its 

 profile were observed to be due sometimes to cross joints, 

 sometimes to basalt dykes which, decomposing, have 

 weathered down much faster than the surrounding 

 granite. The view from Caisteal Abhail, the highest 

 peak (2735 feet) of the ridge, was magnificent, extending 



