"The Knox automobile was a heavy vehicle and was extensively driven in Maine during the winter. Driving along Casco Bay, this automobile has chains on the rear wheels as did most vehicles of the 1909 period, as the tires had no tread molded into them for that extra traction in the ice and snow. Most tires at that time were completely smooth." --Fletcher, David H. "The Portland Company 1846-1982." Charleston, S.C.: Arcadia Pub., 2002. 81.