Scientific American, Vol. 22, No. 21 (May 1870)
A weekly issue of Scientific American from May 1870, published in New York by Munn & Co. for inventors, manufacturers and patent-seeking readers. Wood engravings show patented machinery, oven and steamer apparatus, and a bridge pier in section, drawn in hatched line with lettered callouts on plain grounds, useful for line-art machine parts and industrial diagrams.
