‎"BREWSTER, DAVID. - FOUNDING BIAXAL MINERALOGY.‎
‎On the Affections of Light transmitted through crystallized Bodies. In a Letter to Sir Humphrey Davy. Read December 23, 1813.‎

‎(London, W. Bulmer and Co., 1814). 4to. No wrappers as extracted from ""Philosophical Transactions"" 1814 - Part I. Pp. 187-218 and 3 engraved plate. Fine and clean.‎

Reference : 42349

‎First printing of pioneer paper in which Brewster laid the foundations of new fields of investigations. by showing that in a large class of crystals there are two axes along which there is no double refraction. Such crystals he calls BIAXAL, the simpler type to which Iceland spar belongs being called UNIAXAL.""Brewster created new fields of optical mineralogy and photoelasticity. In 1813, while studying the ""depolarising"" action of Topaz, he observed two sets of elliptical rings (interference patterns) centered on axes in the Topaz that were apparently inclined at 65 degr.. He interpreted this to mean that Topaz must have two axes, not one, of double refraction, an entirely unexpected result. After many laborious experiments he was able in 1819 to group all but a few of hundreds of minerals and crystals into mutually consistent optical and mineralogical categories: the primitive form determined the number of axes of double refraction.""(DSB).‎