Calorific values of American woods
A 1916 University of Illinois thesis by Carl Nathan Davidson measuring the calorific values of American fuelwoods, written for engineers and foresters assessing wood as fuel. The plates are hand-inked line graphs drawn on printed orange-ruled graph paper, plotting percentage loss in weight against hours of heating for maple, poplar, hickory, birch, cherry, pine and oak, with hand-lettered axis labels, small circle and cross data points, and dashed keys.
