Nathan Zeldes once stumbled upon and is now the proud owner of this intriguing artifact: an aerial photography “slide chart” calculator, disguised inside a book, by owner-author C. H. Cornell. Zeldes gives a wonderful breakdown of the components of the chart and calculator and postulates how they might have operated given the technology of their era and its purpose.
At first glance the book “How many?”, by Charles Cornell, seems like any of the small hardcover books common a century ago. But when you open the cover you see it’s just a carefully padded box that contains a strange calculating device, bearing the title “F.24 Photographic Calculator”, and the name of C. H. Cornell.
The calculator would pass for a “slide chart”, that inexpensive poor relation of a slide rule, if it weren’t much thicker and sturdier, and much more complex. To add to the fun, its two faces are entirely covered in low-altitude aerial photographs!
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