xviii THE FRESH- WATER LOCHS OF SCOTLAND 
(r) The volume of water in the lakes of the various river basins 
in millions of cubic feet ; 
(d) The superficial area of the lakes in the various river basins ; 
(e) The extent of the drainage area in the various river basins, 
together with the ratio of the drainage area to the super- 
ficial area of the lakes. 
The information in Table VI. is extracted from the tables given in 
greater detail in the descriptions which will be found in Volume II. 
of this Report. 
From this table it will be seen that 562 lochs have been surveyed, 
and that the number of soundings recorded on the maps of these lochs 
is 59,195. The actual number taken exceeds 60,000. The aggregate 
area of the water- surface is over 340 square miles, and therefore the 
average number of soundings per square mile of surface is 174. 
The aggregate volume of water contained in these 562 lochs is 
estimated at about 1,015,814 millions of cubic feet, or nearly 7 cubic 
miles. The area drained by the lochs is about 6669 square miles, or 
about 19 J times the area of the lochs. 
