262 



Part III. — Fifteenth Annual Report 



VIII. — REPORT ON PHYSICAL OBSERVATIONS BEARING ON 

 THE CIRCULATION OF THE WATER IN LOCH FYNE IN 

 APRIL AND SEPTEMBER 1896. By Hugh Robert Mill, 

 D.Sc, F.R.S.E. 



The observations published in this report were carried out on board 

 the Fishery Board's cruiser 1 Garland ' on two occasions, the first from 

 April 2nd to 6th, and the second from September 3rd to 11th, 1896, 

 with the object of farther investigating the circulation of water in Loch 

 Fyne as influenced by tide and wind. 



Results of earlier Observations. 



Before describing these observations, it is desirable to briefly summarise 

 the results of earlier observations carried out by me for the Scottish Marine 

 Station between 1886 and 1889, which are fully discussed in my paper, on 

 the Clyde Sea Area,* published by the Royal Society of Edinburgh. 



Loch Fyne, from the constriction at Otter Ferry to the head, is a branch 

 of the Clyde Sea Area running on the whole northeastward for 26 miles, 

 following the slight curves of its axis. For the first 20 miles the breadth 

 varies between f and 1 J mile ; then tapering to the head. The total 

 area is 28 J square miles, and it receives drainage from 188 J square miles 

 of land on which the average annual rainfall is estimated to be 70 inches. 

 The total volume of Loch Fyne (as above defined) at low-water is 0*50 

 cubic sea-miles ; and since the average tidal rise over the whole surface is 

 about 8 feet, there is an average increase of 0*029 cubic sea-mile at high- 

 water. The average depth is 22 J fathoms, and the depth along the axis 

 averages 40J fathoms at low tide. 



The outline of Loch Fyne suggests its division into two distiuct parts, 

 which are found to correspond with the conditions of depth also. From 

 Otter Spit to Minard Narrows is a distance of 1\ miles, and this section 

 has been termed the Gortans Basin. The depth in the narrows at Otter 

 is only 15 fathoms, at Minard the much narrower channels are scarcely 

 deeper (17 fathoms), but between them the Gortans Basin sinks to a 

 maximum depth of about 35 fathoms, with a depth exceeding 30 fathoms 

 for 3 miles. Speaking generally, Gortans Basin is a shallow and relatively 

 wide hollow, shut off by bars from the deep Arran Basin (frequently 

 called Lower Loch Fyne) on the seaward side, and from the Upper 

 Basin on the landward side. The small shallow recess of Loch Gair 

 opens on the north-west shore in the middle of Gortans Basin. The 

 Upper Basin, although narrower, is much deeper. The depth increases 

 gently from Minard for 3 miles, until off Furnace it begins to increase 

 abruptly, reaching a maximum of 75 fathoms off Strachur, 3 miles 

 farther, and only beginning to shallow off Strone Point, Inveraray, where 

 the shallow Loch' Shira joins Loch Fyne. The depth in the centre of the 

 Upper Basin is over 60 fathoms for nearly 6 miles. This is the region 

 the circulation of the water in which is of the greatest interest j and in the 

 Upper Basin the herring fishing is sometimes of great importance, 



* Trans. Roy. Soc. Edin., vol. xxxvi. Tart iii. No. 23 (1892), pp. 648, 703-707 ; 

 and vol. xxxviii. Part i. No. 1 (1894) 73-103. 



