1G4 



Drainage hy Steam Power. 



Ft. 



Ft. in. 



2. Bolt, or B. M. (Bench Mark) on tlie Parapet of the Bridge at 

 Crossens. 



-15 



B. M. on Wigan's Lane Bridge, Eufford, near the Engine. 



14 1. Average of High Water, Spring Tides (18 ft. 3 in. above old 

 Dock Sill). 



12 8. Top of Sir Thomas Hesketh's Banks (when put up). 



9 6. Level of Water in the Sluice and on Martin Mere. — Winter of 



1848-9, and on 22nd February, 1852. 

 8 .3. General Surface of Low Land on Martin Mere. 

 7 9^. Breast of Stone- work, over which the wheel throws the Water. 

 7 1. Average of High Water, Neap Tides (lift. Sin. above old 



Dock Sill). 



"5 9. Bottom of Sluice at Wigan's Lane Bridge — near the Engine. 

 4 10. Bottom of Cylinders at Crossens (east end), being the outlet of 

 Martin Mere water. 



4i. Bottom of the Arc of Scoop-wheel at the Engine, 



- Mean Tide Level. Datum of Ordnance Survey. 4 ft. 2 in. above old 

 Dock Sill (or, according to some, 4ft. 9 in.). 



4 2. Sill of old Dock Gates at Livei'pool, from which the heights of 

 the Tides are given. 



1- 5 11., Average Low Water of Neap Tides (1ft. 9 in. below Dock 

 Sill). 



-9 5. Mean Low Water, being the average of Spring and Neap Tides. 



-12 11. Average Low Water of Spring Tides (8 ft. 9 in. below Deck 

 Sill). " 



N.B.— The lowest tide in 1852 is 10 ft. Sin Tth October. 

 The highest do. . . 21 11 6th April. 

 Example. — A tide of 12 ft. 5 in. is level with the general surface of the low land 

 cn Martin Mere, which it will be seen is 8 ft. 3 in. above the mean tide level. 



