May 17, 1900] 



NA TURE 



65 



THE FRESH-WATER LOCHS OF SCOTLAND} 



'T'HE introduction to this paper, published in the Geographical 

 -*• Journal, includes the correspondence that passed between 

 the Royal Societies of London and Edinburgh and Her Majesty's 

 Treasury in 1883 and 1884, relative to the survey by a Govern- 

 ment Department of some of the inland lakes of Scotland. 



The weighty arguments brought to bear upon the Government 

 by these learned societies failed in their object, and the Govern- 

 ment declined to undertake the proposed surveys. In these 

 circumstances the authors determined a few years ago to make 

 a systematic survey of all the fresh- water lochs of Scotland, and 

 the present paper is the first instalment in the publication of 

 their results, dealing with a compact series of lakes directly or 

 indirectly connected with the water-supply to the city of 

 Glasgow, viz. Lochs Katrine, Arklet, Achray, Vennachar, 

 Drunkie, Veil, Doine and Lubnaig, which form part of one 

 united drainage system having its outflow by the River Teitli. 



F. P. Pullar's sounding machii 



In order to overtake the large amount of work contemplated, 

 involving an immense number of soundings, within a reasonable 

 time, it was necessary to have a portable wire sounding machine 

 adapted for rapid work in small rowing boats. Mr. PuUar 

 designed, and had made, a sounding machine (see Fig. i), which 

 is described and figured ; this apparatus is admirably adapted for 

 the purpose in view, and with it all the soundings in the different 

 lakes were taken. 



The total number of soundings recorded in the paper, taken 

 in the eight lochs mentioned, was 2422, the number varying 

 from 775 in the largest (Loch Katrine) to 90 in the smallest 

 (I^ch Doine). These soundings were laid down in position on 

 the large scale (six-inch) Ordnance Survey maps, and contour- 

 lines of depth drawn at certain intervals, from which with the 

 aid of the planiriineter the cubic mass of water in each loch was 



1 " A Bathymetrical Survey of the Fresh-water Lochs of Scotland. " By 

 .'u-l°*L" '^i"f''''y- KC.ll> D.Sc, F.R.S., and Fred. P. Pullar, Esq.', 

 I K.O.S. Part 1. The Lochs of the Trossachs and Callander District. 



calculated. The soundings'Jihow that Lochs Katrine, Arklet, 



Achray, Voil and Doine form each a single basin, while in 



Lochs Lubnaig, Drunkie and Vennachar 



the irregularities of the bottom cut up the 



deep parts of the lochs into separate 



basins. 



The most important of the lakes under 

 consideration is the well-known Loch 

 Katrine, which is eight miles in length, 

 one mile in maximum width, with an area 

 of 4iJ square miles. The greatest depth, 

 495 feet (824 fathoms), was found much 

 nearer the eastern than the western end, 

 so that a section drawn down the centre of 

 the loch from west to east (see Fig. 2) 

 shows a gradual increase of depth for 

 nearly four-fifths of the total length, and 

 then a more rapid rise of the bottom to- 

 wards the eastern end. A section across 

 the loch from north to south (see P^ig. 3) 

 .shows the deeper part at the point chosen 

 for the section nearer the southern than 

 the northern shore. The mean depth of 

 the loch, i.e. the cubic mass of water 

 divided by the area, is 199 feet. The sur- 

 face of the loch lies at an elevation of 364 

 feet above the sea, hence a considerable 

 portion of the bottom (over one square 

 mile) falls below the level of the sea ; in 

 this respect Loch Katrine differs from all 

 the other lochs treated of. In connection 

 with the water-supply to Glasgow, Loch 

 Katrine was raised four feet above its pre- 

 vious level, and it is now in process of 

 bemg raised an additional five feet. 



Loch Arklet is a small Highland loch 

 situated between Lochs Katrine and Lo- 

 mond, at an elevation of 455 feet above 

 the sea. It is over a mile in length, nearly 

 half a mile in maximum width, and covers 

 an area of about one-third of a square 

 mile. The greatest depth, 67 feet, was 

 found nearer the western than the eastern 

 end ; the mean depth is 24 feet. Loch 

 Arklet at present belongs to the watershed 

 of Loch Lomond, but the Corporation of 

 Glasgow have power to divert its waters 

 into the Loch Katrine watershed, with the 

 view of increasing the supply of water to 

 that city. 



Loch Achray is situated between Lochs 

 Katrine and Vennachar, at an elevation of 

 276 feet above the sea. It receives the 

 outflow from Loch Katrine and flows into 

 Loch Vennachar, the level of which is six 

 feet lower. Loch Achray is about i^ miles 

 in length, and one-third of a mile in maxi- 

 mum width, covering an area of about 

 one-third of a square mile. The greatest 

 depth, 97 feet, was recorded in two places 

 approximately in the centre of the loch ; 



the mean depth is 36 



feet. 



Loch Vennachar is 



about four miles in 



length, with a maxi- 

 mum breadth of less 



than three-quarters of 



a mile, and covers an 



area of over i i square 



miles. The greatest 



depth, 1 1 1 feet, is 



situated approximate- 

 ly in the centre of the 



loch ; the mean depth 



is 42^ feet. Loch 



Vennachar has been 



raised five feet nine 

 inches in connection with he Glasgow water-supply, for the 

 purpose of providing compensation water to the River Teith. 



Fig. 



•Transverse 

 section of Ix)ch 

 Katrine. The black 

 portion shows the 

 true slopes ; the out- 

 line shows the slopes 

 ex.iggerated ten 

 times. 



Fig. 2.— Longitudi 

 iial section of Loch 

 K.-itrine along the 

 axis of ir.aximum 

 depth. '1 he black 

 portion shows the 

 true slopes ; the 

 outline shows the 

 slopes exaggerated 

 ten time.s. 



NO. 1594. VOL. 62] 



