Figure from Stephen Johnston, ‘Making mathematical practice: gentlemen, practitioners and artisans in Elizabethan England’ (Ph.D. Cambridge, 1994). See the contents page for direct access to the chapters and the image gallery for the figures currently available online.

Figure 3.11

Fragments, p. 65. ‘This scale doth show the proportion that one ship doth bear to another.’

Judging from the still-visible scribed lines, this scale was extensively used. The proportional amounts by which the later columns exceed the first are marked at their tops. The columns are designed to be read at the side with the finest divisions. The scale can be used for ships whose tonnage is in the ratio 8/7, 7/6, 6/5, 5/4, 4/3, 7/5, 3/2, 8/5, 7/4 or 2/1.

Example. If a ship of 200 tons with depth 13ft is to be taken as the model for a ship of 400 tons, the index is placed across 13 on the first column. On the final column the depth for the second ship appears as just less than 16½ft. (Working with the pen or calculator gives the second depth as 16.38ft.)

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