Original echo soundings of Windermere by Admiralty. 1937. Also smaller scale survey of Coniston, Ullswater, Derwent, Buttermere. PB Basement plan chest
Echo sounding survey: Field books of Esthwaite, Grasmere, Thirlmere, Lowes Water, Ennerdale, Bassenthwaite, Wastwater. 1937.
Drawings of Haweswater lake level
Correspondence between Mortimer, Eric Ramsbottom (1960s), W.J Farquharson of the Hydrographic Department (Admirality) and A.N. Wilson (1937-1950), Borough Engineer and Surveyor over over echo sounding charts, depth survey of Ennerdale Lake with echo sounding apparatus.
Charts of 'soft' sediments as shown by Kelvin Hughes echo-sounder, 1937-38. Windermere & other lakes, including Esthwaite, Ullswater, and Thirlmere. Echo sounding Record book, further annotated by CHM in 1975.