460 MR J. Y. BUCHANAN, F.R.S., ON THE 



the clay or mud formed a large percentage of the mass, either as interbedded layers or 

 as pockets, and in some of these pockets Foraminifera were to be seen. Amongst the 

 collection were two ear-bones of whales and a very fresh shark's tooth, covered with the 

 incrustation. The occasional occurrence of icebergs at the surface was made probable by 

 the presence of two pieces of granite, the one with a very thin covering, and the other 

 with over one-eighth of an inch thickness of manganese. On the fracture of one of the 

 pieces, it was evident that the manganese had filtered into the interior of the stone, 

 colouring the quartz a beautiful amethyst purple." 



This haul was remarkable in many ways ; and not the least in being the only 

 important haul which we got in the vicinity of continental land, and with no volcanic 

 islands near. The samples taken for analysis were — 



I. The outer rind or shell of a spherical nodule, which was detached without 



any trace of the kernel. It was 1 millimetres thick. 

 II. A similar piece, detached from another spherical nodule, but with traces of 



the kernel attached. It was also 10 millimetres thick. 

 III. A piece of a horizontally stratified concretion, with botryoidal upper surface. 

 It was 15 millimetres thick. 



Samples marked IV. and V. are from one nodule. IV. is part of the outer rind, 

 13 millimetres thick, consisting of concentric layers, most of them mottled with reddish 

 yellow spots, and separated by fine seams of purple-brown oxide of manganese, without 

 yellow specks. V. is the kernel of the same nodule. It is harder than the rind, from 

 which it easily splits away. It is nearly spherical, with a radius of 16 millimetres. At 

 the centre is a small colourless piece of mineral matter. 



This nodule was one of an enormous haul made by the "Challenger" on the 12th 

 July 1875 in the North Pacific, in lat. 37° 52' N., long. 160° 17' W. The depth of the 

 water was 2740 fathoms. The temperature of the bottom water was 1"0° C, and its 

 density at 15"56° C. was 1 "02573. The gaseous contents of the water were — 17'7 c.c. 

 mixed nitrogen and oxygen, of which 16"95 per cent, was oxygen, and 21 '48 c.c, or 

 42 milligrammes, carbonic acid per litre. It will be seen that the water contains very 

 much less oxygen than was contained in the bottom water off the Australian coast. In 

 fact, in this water the dissolved oxygen has been reduced to almost exactly half the 

 amount which it contained when it left the surface. All over this district, where 

 manganese greatly abounds, the dissolved oxygen has been reduced from 34 per cent, of 

 the mixed gases, as at the surface, to from 16 to 22 per cent, at the bottom. 



The position of this station lies midway between the Aleutian Islands and the 

 Sandwich Islands, being 1000 miles distant from the nearest island of either group; it 

 is 1600 miles distant from the nearest point of the North American continent in the 

 same latitude. Hence, although there were many stations further from land than this, 

 it can claim to be quite beyond the reach of any continental influence. The station from 

 which samples I., II., and III. come, although comparatively close to the Australian coast, 



