The cost of operation of a central heat, light, and power plant
An 1902 engineering thesis by Charles Leonard Samson and Edwin Gardner Greenman at the University of Illinois, recording running costs of a campus central heat, light, and power plant for fellow engineers. Its plates are hand-inked line graphs on printed yellow-green grid paper, pairing outside temperature with boiler horsepower, useful for jagged data lines, ruled grounds, and drafted capital lettering.
