THE FIRST SIX BOOKS,

TOGETHER WITH THE

ELEVENTH AND TWELFTH.

The Errors, by which THEON, or others, have long ago
vitiated these Books, are corrected,

And fome of EUCLID's Demonstrations are restored.

ALSO

THE BOOK OF

EUCLID'S DAT

In like manner corrected.

BY

ROBERT SIMSON, M. D.

meritus Professor of Mathematics in the University of Glasgow.

To this SIXTH EDITION are also annexed,

LEMENTS of PLAIN and SPHERICAL TRIGONOMETRY.

EDINBURGH:

rinted for J. NOURSE, London, and J. BALFOUR, Edinburgh.
M,DCC, LXXXI.

KING,

THIS EDITION

OFTHE

PRINCIPAL BOOKS

OFTHE

ELEMENTS OF EUCLID,

AND OF THE

BOOK OF HIS DATA,

IS MOST HUMBLY DEDICATED,

BY

HIS MAJESTY's

MOST DUTIFUL, AND

MOST DEVOTED

SUBJECT AND SERVANT,

ROBERT SIMSON.