THE SLIDE RULES DESIGNED BY F. BLANC, J. ST. VINCENT PLETTS, AND ALBERT F. PUCHSTEIN
My JOS article on hyperbolic slide rules was completed for printing a few weeks before the above listing was prepared to go on the JOS web site. In the interim period I was browsing through some past JOS Volumes and came upon an article that is of real interest. It is something that would have been nice to know ahead of time so that it could have been included in my JOS article. It is being reported here to complete the historical record. In JOS Vol. 4, No. 2, Rodger Shepherd presented a description of a slide rule designed in 1890 by F. Blanc. This slide rule was the first design to show a way to obtain the hyperbolic functions. In JOS Vol. 5, No. 1, further information on this slide rule was furnished in a letter submitted by Dr. Gunter Kugel. Although Blanc's slide rule did not have actual hyberbolic scales it did have marks on it whereby, when the conversion to base e was made, the values of Sinh and Cosh could be obtained. This slide rule is a major historical landmark in the history of hyperbolic rules, but unforunately no picture of it seems to exist. It seems Blanc submitted a Patent, but it was not issued and the slide rule was never manufactured. Peter Holland, in response to my questions for information, contacted Dr. Kugel, who said that he tried to construct the Blanc slide rule but was not successful. It seems the slide rule, if completed, would have been at least one and a half meters long. Also, a circular version may have been completed at the University of Frankfurt. Will continue efforts to obtain more information and a picture, if possible. After reading about the Blanc slide rule I contacted Rodger Shepherd, the author of the JOS Vol. 4, No. 2 article. He has been very helpful in sending me additional articles on the history of hyperbolic slide rules. One he sent me is copy of a paper from Vol. 33, Part 2, of the Proceedings of The Physical Society of London, dated February 15, 1921. The title of this paper was Some Slide Rule Improvements, by J. St. Vincent Pletts. This Article is important as it seems to be the first to show a picture of a slide rule with hyperbolic scales. It also predates Puchstein's patent No. 1,487,805; filed May 12, 1921 by about three months. These two 1921 slide rules were not manufactured, and the proximity of dates appears to be just a coincidence as there is just no resemblance betwween the pictures of the scale layouts on the Pletts' and Puchstein's slide rules. Although Blanc's, Pletts's, and Puchstein's designs predated the K&E 4093-3 we need to keep in mind that the K&E 4093-3 was the first hyperbolic slide rule to be actually manufactured and sold to the public. See the K&E Slide Rules Appendix.