The PREFACE. Perſpective was not neglected. He has car-
ried the Matter farther than could have been
reaſonably expected from one ignorant of
Mathematicks; and I am indebted to him
for ſeveral Obſervations, which I my ſelf
ſhould perhaps have never thought on.

7. ERRATA.

Page 74. 1. 17. for x, r. in X.

P. 83. 1. 28. for that, r. that for.

P. 88. 1. 8. for Tube, r. Table.