The Civil engineer and architect's journal, scientific and railway gazette (1839)
London : [William Laxton] · leaf 303
ouud that the draughts-man did not hold the pricker perpendicular; consequently, thelower sheets could not be accurate copies of the original. Toobviate this, I have contrived an instrument, by which any atten-tion on the part of the draughtsman in keeping it perpendicularis not required: all he…
Architecture · Civil engineering · Science
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