DOLLOND, JOHN. - MEASURING SMALL ANGLES.

Explanatio novae rationis, Angulos, sub quibus obiecta in telescopiis spectantur, metiendi. Excerpta ex Transact. Philosop. Vol. XLVIII...ex Anglio sermonte translata.

Leipzig, Gleditsch & Lanckisiii, 1756. 4to. No wrappers. In: "Nova Acta Eruditorum", Anno 1756, No. X (September issue). Pp. 481-528 (entire issue offered). Dollonds paper: pp. 496-505 and 1 engraved plate. Wide-margined. Some browning and brownspots.

First Latin edition of Dollond's importent paper "An Explanation of an Instrument for measuring Small Angles," pawing the way for his invention of the Acromatic Telescope. The paper was first printed in The Philosophical Transactions, 1754. The plate shows the combination of two lenses of crown glass and flint glass correcting the errors arising from the different refrangibility of the rays of light.

Order-nr.: 45593