452 



NATURE 



[March 8, 1888 



Philippines, by M. O. Beauregard. This is a lengthy treatise 

 on the products, language, sociology, and history of the islands, 

 based chiefly on Spanish authorities, — Report, by M. Topinard, 

 of the excavation of the Neolithic grotto of Feigneux (Oise), in 

 which was found a skull that had been trepanned both before 

 and after death. These finds were specially rich, including four 

 skulls which bore traces of having been compressed ; and, con- 

 sidered generally, this deposit may be regarded as a pendant to 

 that of Orrouy.— (i) On a burial ground of the Stone Age at 

 Crecy-en-Brie ; (2) on cut flints in the alluvial sand below Paris ; 

 and (3) on a prehistoric work-place at Fontenay-aux- Roses, byiM. 

 Thieullen. The writer draws attention to the frequency with 

 which the larger debris of cut flints are found near water, and 

 always in localities favourable to the existence of prehistoric 

 man, while from the character of the great ossuaries, in which, 

 as at Crecy-en-Brie, the remains of men and women of all ages, 

 and children, are found, he believes we may assume that the men 

 of the period lived in family rather than in tribal association. — 

 A study of the brain of Bertillon, by MM. Chudzinski and 

 Manouvrier. A resume of the results of this carefully con- 

 ducted cerebral analysis, which are here given in detail, shows 

 generally, inter alia, a large development of the anterior portion 

 of the brain in all directions ; a relatively inferior development in 

 point of size in the temporal lobes, and in the cerebellum ; and 

 great ramification in the fossae. 



The Izvestia of the Ru*ssian Geographical Society (xxiii. 

 part 5) contains, besides Dr. Bunge's preliminary report 

 about his expedition to the New Siberia Islands, a lecture 

 on the problems of scientific geography by Dr. Petri, who was 

 appointed in October last Professor of Geography and Anthropo- 

 logy at the St. Petersburg University ; a paper by M. Rovinsky 

 on the beliefs of the Montenegrins ; M. Nikolsky's sketch of 

 fishing on Lake Aral, a valuable contribution to the know- 

 ledge of the fishes inhabiting Lake Aral, and especially the 

 lower Amu-daria, their habits, and the modes of fishing ; and 

 notes by General Stebnitsky on recent pendulum observations, 

 on M. Boguslavsky's work on the Volga, and on W. J. Havenga's 

 map of Sumatra. 



SOCIETIES AND ACADEMIES. 

 London. 



Royal Society, February 2.— "On Tidal Currents in the 

 Open Ocean." By J. Y. Buchanan, F.R.S. 



This paper gives details of some current observations which I 

 made in the open ocean north of the Canary Islands in October 

 1883 in the cour-e of the surveying expedition preliminary 

 to the laying of a telegraph cable between these islands 

 and the mainland of Spain. This expedition consisted of two 

 steamers, the Dacia and the International, belonging to the 

 India-rubber, Gutta-percha, and Telegraph Works Company 

 (Limited), of Silvertown. The chief scientific results gained 

 during it were the confirmation of the view — which was sug- 

 gested by the density and temperature of the bottom water 

 observed in this part of the Atlantic during the cruise of the 

 Challenger — that the overflow of warm concentrated sea-water 

 from the Mediterranean at the bottom of the Straits of Gibraltar 

 was the cause of the abnormally high density and temperature of 

 the bottom water in this part of the ocean, and the preparation 

 of a complete survey of the bed of the ocean in this district. 

 During the progress of the work several very remarkable 

 "oceanic shoals" were discovered and surveyed, notably the 

 "Coral Patch" in lat. 34° 57' N., long. 11° 57' W., with a 

 depth of 400 to 500 fathoms, and the "Dacia Bank," in lat. 

 31° 9' N., long. 13° 34' W., with a minimum depth of 49 

 fathoms. In sounding over both of these banks conclusive 

 evidence was obtained of the existence of actual vertical preci- 

 pices in some positions on their flanks ; and from the very great 

 average steepness all round, it is rendered in every way probable 

 that, if they were laid dry, they would form mountain peaks as 

 precipitous and inaccessible as any to be found on land. The 

 dredging on the Coral Patch showed it to consist of deep-sea 

 corals, principally Lophohelia prolifera, growing with the utmost 

 luxuriance and attached to dead stems of the same species, 

 already getting coated with peroxide of manganese. 



For the purposes of the survey of the " Dacia Bank " a buoy 

 was anchored on its eige, and on the afternoon of October 21 I 



spent some hours in a boat made fast to it, and observed the 

 current in strength and direction. The following is a summary 

 of the results : — 



Hour p.m 2.15 ... 2.40 



Direction (true) ... N. ii"E. ... N. 41° ^ 

 Rate (knots per hour) 0*47 ... ^^ o'3o 



46 



3.30 ... 4.6 

 ... N. 56° E. ... N. 101° : 

 026 ... o'30 



It will be seen from these observations that in two hours the 

 current had shifted its direction through 90°, and had passed 

 through a minimum velocity of o''26 per hour without there 

 having been any period of " slack water." The observations 

 are too few in number to make it worth while submitting them 

 to analysis ; but a little study of them will show that they 

 indicate a current which is the resultant of a continuous current 

 and a periodic one. A constant current running south-east 

 by east, combined with a tidal current running north-north- 

 west and south-south-east, the maximum velocity of which, in 

 either direction, is twice that of the permanent current, would 

 give a resultant agreeing fairly with that observed. 



No measurements were made of the under current, but, by 

 sinking a tow-net made fast to a sounding-line, it was seen to be 

 running at a depth of 75 fathoms in the same direction as the 

 surface current and apparently with much the same velocity. In 

 the channels between the Canary Islands, where even on the 

 shallowest ridges there is over 1000 fathoms of water, the tidal 

 current reaches to the very bottom, and its scouring action is 

 shown by the nature of the bottom. To seaward, in 1800 or 

 2000 fathoms, the bottom is a fine Globigerina ooze, which gets 

 coarser and sandier as the water shoals in the channels, till on 

 the summit ridge there is generally no loose deposit at all, and 

 the bottom is rock or coral coated with black oxide of man- 

 ganese. Round the western end of Tenerifife the tide runs 

 violently, causing rips and overfalls. Much rocky ground is 

 met with in the North Atlantic in depths of 1300 and 1400 

 fathoms, especially on the ridge which appears to extend through 

 the whole length of that ocean. It is not unlikely that the 

 summit edge of this ridge may be swept clean through the 

 greater part of its length, and it must be remembered that the 

 removal of sediment from one part of the ocean bottom means 

 its deposit in greater abundance in others, especially in hollows 

 in the neighbourhood of the ridge. Hence a sounding in 

 "ooze" or "mud" in one position furnishes no argument 

 against the trustworthiness of another sounding in the vicinity 

 and in equally deep water on " rock " or " hard ground." 



It is evident, then, that the power of shoals to transform the 

 tidal wave into tidal currents furnishes a natural agency which 

 tends to limit the indefinite shoaling of the water by the con- 

 tinual deposition of loose sediment. On the other hand, these 

 currents, in sweeping clean the rocky eminences at the bottom 

 of the ocean, prepare a lodging-place for deep-sea corals, and 

 assist in bringing fool to them when settled, thus enabling them 

 to build up their pillar-like banks, of which a very fine example 

 is furnished by the "Coral Patch" above referred to. There 

 can be little doubt that it is reducing more or less rapidly the 

 depth of the water above it. The "Dacia Bank" and the 

 " Seine Bank " are examples where limiting conditions, 

 probably of temperature, appear to have been reached. The 

 water may be too warm for the deep-sea species ; and not warm 

 enough for the tropical, par excellence, reef-building species. 



A remarkable cluster of banks resembling those above 

 described occurs off the Brazilian coast, between the Agulhas 

 reef and the islands of Trinidad and Martin Vaz Some of 

 them are named, as the Jaseur, the Montague, and the Victoria 

 banks ; with from 25 to 30 fathoms, and completely surrounded 

 by deep water. Further north is the dangerous Rocas, lying 

 close to the route of steamers from North America and Europe 

 to South American ports. Further south, again, are two sug- 

 gestive soundings, one of 19 fathoms, in lat. 32°40'S., long. 

 47° o' W., marked "Nelson, 1859," and the other of 72 fathoms, 

 in lat. 37° 50' S., long. 49° 50' W., marked " Sutlej, 1863," in 

 the chart. Seamen are not usually mistaken as to whether they 

 have or have not found bottom in depths such as 19 or 72 

 fathoms, and there is little doubt that careful search would 

 reveal the existence of shoals in these localities. But the search 

 must be diligent and methodical, always following the lead of 

 the soundings as they shoal. The careful and detailed study of 

 these oceanic shoals or embryo islands is of great importance for 

 oceanographical science, and it would not be easy to find more 

 interesting work for the marine surveyor. 



