COMPOSITION OF OCEANIC AND LITTORAL MANGANESE NODULES. 



461 



may be said also to be practically beyond the sphere of its influence, as, owing to its 

 climate, it is almost destitute of drainage. 



The Littoral Nodules, samples M, N, P, Q, K, E, &c, are from Loch Fyne, one of 

 the most important arms of the Firth of Clyde. They are from a lump of mud which 

 came up on the fluke of the deep-sea kedge-anchor of the steam yacht " Mallard " after a 

 series of temperature observations in the deepest part of the loch on the 21st September 

 1878. 



The Firth of Clyde is the name given to the most remarkable group of fiord-like 

 channels and sea lochs in the British Islands. They form a compact basin or depression, 

 and it has been named after the principal stream which empties itself into it — the river 

 Clyde. If we draw a straight line through the Craig of Ailsa and Sanda Island, at the 

 extremity of the Peninsula of Can tyre, we shall have delineated the Firth seawards, and 

 a line of soundings along this line discloses an almost perfectly uniform depth of water 

 of from 23 to 25 fathoms. If we run a line of soundings at right angles to this line, 

 we shall find the water deepening as we retire from the line whether we go north- 

 wards or southwards. If we go northwards we find the depth increase gradually 

 and steadily as we pass the Island of Arran, whether by the main channel on the 

 east, or by Kilbrennan Sound on the west ; so that Arran stands, as it were, on an 



6!W 



N 65' 



107715 



Cables 



I I I L 



Sea Mile' 



Loch Fyne. Section I. — Can tyre to Cowal. 



inclined plane sloping northwards from the north of the Firth, attaining a depth of 

 90 fathoms off the N.E. point of the island, and continuing as a deep trough into 

 Loch Fyne, with a maximum depth of 104 fathoms"" close to Skate Island and about 

 three miles from the entrance of the loch. This deep trough only occupies a portion of 

 the width of the loch, as is shown by the chart and sections. At its mouth the loch 

 measures four nautical miles across, but the width of the portion of it over 50 fathoms in 

 depth is only one mile. Both the loch, as a whole, and the deep channel contract until 

 they reach a minimum of sectional area, where this deep spot is. Here the whole width 

 across from Skate Island to the south shore is only 1 '6 mile, and of this one-half, or 



* See Map. 



