It is the concentration of lakes, set within a series of radiating valleys, which more than anything else has stamped an almost unique imprint on the landscape of this corner of EnglandSpa hotel lake district . To the eighteenth century topographic writers, it was simply 'The Lakes'. Lacking any scientific evidence to support or disprove their views, estimates of the depth of the various lakes varied between wide limits. A lake like Derwentwater, with its island, was not considered very deep. Pennant, the eighteenth century traveller, in extolling the virtues of Keswick as a tourist centre, urged the visitor to 'Take boat on the water which makes the place so justly celebrated.
The form is irregular, extending from north to south, above three miles and a half, the breadth one and a half. The greatest depth is twenty feet in a channel running from end to end, probably formed by the river Der¬went which passes through and gives its name to the lake.' As it later turned out, Pennant's estimate of depth was badly out but it was in keeping with the view that the lake was resistively shallow. Wastwater, on the other hand, was looked upon almost as a bottomless pit. With its dark screes plunging steeply into the south side of the lake and casting an overall gloom, it was clearly very different from Derwentwater or even Windermere.
The early guide books seldom included it because of its inaccessibility even for the most penetrating tourist. Jonathan Otley in the later edition of his Descriptive Guide remarked that 'it has recently been sounded to a depth of forty five fathoms; but we have been told of a par¬ticular shot, when a line of double the length did not reach the bottom; which must at any rate be several fathoms below the level of the sea. It is probably owing to its great depth, in proportion to the extent of surface, that it has never been known to freeze.' Local hearsay suggesting a depth of ninety fathoms or more has proved a gross exaggeration and the originally sounded depth of forty¬ five fathoms is much nearer the truth. Otley's suggestion that the deepest part of the lake might be below sea level has however been confirmed by later soundings.
Our knowledge of the depths and form of the lake basins dates from the end of last century when Hugh Robert Mill and some associates began a systematic survey. Working from a rowing boat and sounding with a lead line, Mill made a number of traverses of each lake. From the depths he obtained, contour lines were inserted and it is these which are shown on the current Ordnance Survey Tourist map. Although James Clarke had published a folio volume of A Survey of the Lakes of Cumberland, Westmorland and Lancashire as early as 1787, and Peter Crosthwaite, self styled 'Admiral of the Keswick Regattas and Hydro¬grapher to the Nobility and Gentry', made a series of rough maps of some of the lakes between 1792 and 1810, Mill's detailed surveys from 1893 onwards gave the first true picture of the lake basins. He was at pains to point out that their form varied considerably. Derwentwater, for example, had a very uneven bed of glacial debris. A central ridge which came to the surface in Derwent Isle and St Herbert's Island might be a partially submerged esker for it is composed of flat stones.