Campbell's Mill, Akatarawa - Nattrass Rail Tractor, built in New Zealand in 1923 and only the second manufactured from a design patented by race car driver, car salesman, and inventor Howard Nattrass, who was the winning driver of the 1921 New Zealand Motor Cup.
In November 1924 Nattrass was granted the patent for his rail tractors using Fordson farm tractor engines and transmissions, or V8 Cadillac. The Nattrass was a simple, lightweight machine, available at an affordable price which allowed sawmillers to expand their operations into areas previously inaccessible with horse teams.
According to the description on the photo, the Nattrass will perform on a ".... bush tramway with severe curves and grades up to 1" in 5' 6"...."
The rail tractor is shown hauling a log that has part of its length obscured behind a cutting and bend in the line. The hidden end of the log is supported by a log bogie in tow.