Volume Eleven - Pre-Victorian to the Present Day - some more aspects - The Steam Navvy and the Dock Extension of 1883 . . .

The following results, obtained directly from contractors using the navvy, show a substantial agreement in this respect.

It is difficult, to estimate the cost of doing the same amount of work by hand, but a saving of 2d. to 6d. per cubic yard may be safely reckoned upon. Where the stuff is hard it is still greater. For stiff brown clay 10¾d. per yard has been given as the cost ; and for stiff hard tough clay, containing boulders weighing from ½ cwt. to 4 tons, the cost was estimated at 1s. 6d. per cubic yard by hand labour, whilst the cost was 4¾d. by the machine, which was one of the earliest sent out. With the present stronger machines the cost would have been still less ; in short the harder the stuff, the greater is the economy over handwork.

Equivalent Hand Labour. — The number of men required to do the work by hand will vary very much. For instance, in excavating 190 cubic yards per day the following men were necessary : one ganger, ten gullet men, seventeen wingmen, two platelayers, one brakesman, two horses and two drivers ; or a total of thirty-three men and two horses.

At the same rate to excavate by hand 600 yards per day, as the navvy does, ninety men would be required. The steam navvy may therefore be considered equal to at least sixty or seventy men.