"Shown here is a remarkable early engineering drawing of a lighthouse fog whistle, boiler, and timing mechanism produced in 1868. This drawing is one of of over 12,000 engineering drawings in the Portland Company Collection at the Maine Historical Society in Portland, Maine. These drawings cover a 100-year period and are of many subjects, and copies as well as photographs may be purchased from this collection." --Fletcher, David H. "The Portland Company 1846-1982," Charleston, S.C.; Arcadia Pub., 2002, 104.