This section is from the book "The English And American Mechanic", by B. Frank Van Cleve. Also available from Amazon: The English And American Mechanic.
Width at bottom = .7 height; at middle = .5 height; and at top = .3 height.
PURPOSE. | Formation of Strata. | Extreme Height. | Extreme Width. | Depth at Crown. | |||
Feet. | Ins | Feet. | Ins. | Feet. | Ins. | ||
Canal................ | Various.......... | 16 | 2 | 17 | 1 | 3 | |
Canal.......... | Clay....................... | 21 | 6 | 20 | 1 | 6 | |
Thames Tunnel.... | Clay.............. | 22 | 3 | 37 | 6 | 2 | 6 |
Railway........... | Chalk.................... | 26 | 6 | 27 | 1 | 6 | |
" | Various | 27 | 6 | 27 | 1 | 10½ | |
" | Shale..................... | 30 | 30 | 1 | 10½ | ||
" | Green sand......... | 30 | 6 | 30 | 2 | 3 | |
" | Freestone.......... | 36 | 36 | 2 | 3 | ||
Canal.................... | Chalk and earth.. | 39 | 35 | 6 | 1 | 2 |
 
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