JF Ptak Science Books LLC Post 703 Blog Bookstore
I’ve seen a number of unusual calculating machines, but this one–patented by Marshall Smith in 1876) seems one of the smallest, and efficient–if not limited–varities. It is the second edition so-to-speak of a mechanical, graphite pencil, operating this time without rotors or any other internal mechanical devices. It was evidently a big seller–hosted in part, so it seems, by The Scientific American itself–having sold some 5,000 units.