A new and complete dictionary of arts and sciences : comprehending all the branches of useful knowledge, with accurate descriptions as well of the various machines, instruments, tools, figures, and schemes necessary for illustrating them, as of the classes, kinds, preparations, and uses of natural productions, whether animals, vegetables, minerals, fossils, or fluids : together with the kingdoms, provinces, cities, towns, and other remarkable places throughout the world : illustrated with above three hundred copper-plates, engraved by Mr. Jefferys, geographer to His Majesty : the whole extracted from the best authors in all languages (1763)

Society of Arts (Great Britain). Society of Gentlemen, Jefferys, Thomas, -1771, Grignion, Charles, 1721-1810, Wale, Samuel, d. 1786, Owen, W. (William), d. 1793 · London : Printed for W. Owen, at Homer's Head, in Fleet-Street · leaf 287

An illustration from A new and complete dictionary of arts and sciences : comprehending all the branches of useful knowledge, with accurate descriptions as well of the various machines, instruments, tools, figures, and schemes necessary for illustrating them, as of the classes, kinds, preparations, and uses of natural productions, whether animals, vegetables, minerals, fossils, or fluids : together with the kingdoms, provinces, cities, towns, and other remarkable places throughout the world : illustrated with above three hundred copper-plates, engraved by Mr. Jefferys, geographer to His Majesty : the whole extracted from the best authors in all languages, 1763, leaf 287 — r, and Iobferve the index is turned juft onceround, while the point 0 pafies over it.Then it is plain the diameter of the hairin the image is -?0- of an inch. Now ifthe microfcope, IDEFdef, magnifies6 times, or makes the image 6 timeslarger in diameter than the object,then is the diameter of the… … <Ufl/.Yf,*<*fl MIC [ 2099 on the micrometer-plate, fo each of thofefmall divifions are the ^6 of T%, or theTJL^ part of an inch. Therefore, if, inmeasuring any part of an object, you ob-ferve how many of tliefe finaller divifionsare patted over by the index, you willhave fo many thoufandth…

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