In particular:
- p7. "rceiving" changed to "receiving".
- p11. "wabble" has been left - it appears to be a variant spelling of wobble.
- p18. "overhanging ledges or these materials" changed to "overhanging ledges of these materials".
- p22. "only few men" changed to "only a few men"
- TABLE II.
"Loose gravel 1 30 1 30 2 60 3 90 4 12"
changed to
"Loose gravel 1 30 1 30 2 60 3 90 4 120" - p50. "steam or air driver" change to "steam or air driven"