Letter, from John Elton to Cromwell Mortimer, dated at London Covering letter enclosing a paper with a description of a new quadrant which can take altitudes without an horizon Paper explains how to use the quadrant with an engraving of it Note states: 'Not to be entered [in the Letter Book]' Printed in 'Philosophical Transaction', vol 37, no 423, p 273 15 July 1732