Wedge line ruler
Date
Circa 1893
Description
Rectangular glass wedge consisting of two layers. Has metal device on two sides. Marked 1/160; Henry Joseph Grayson designed and made a machine which enabled him to rule up to 120,000 lines to the inch for use in microscopy. The glass wedges were used for ruling the different bands. Each one was for a particular band. The one with the slope of 1 in 160 was for the 120 000 band. For the use of the wedges refer to the paper by Stone, page 11, fig 2. William Stone's daughter, Mrs M Murray's estate was presented to the Department of Medical History
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