I take this opportunity of correcting some errors which I have detected, or which have been pointed out to me, in the " Elementary Course of Mathematics."

Page 195. In the figure the weight W is made to act upon the right hand side of the wheel, instead of the left.

Page 224, line 17. For first read here.

In the figure of page 417, the arrows should point in the opposite direction, in order to shew the true direction of the Earth's motion; and in the figures of pp. 418, 423, and 462, the ecliptic and equator ought to change places; but the explanations are not at all affected.

Page 436, line 1. For great read small.

In figure of page 445 insert P' at the point corresponding to P which is to the left of the line NN'.

of the two," read, "the same

Page 455, line 21. For the sentence "but if will be the case when the sun and moon are on opposite sides, or the moon in geocentric opposition; when the moon is halfway between opposition and conjunction the effect may be considered to be the difference of those due to the lunar and solar action."

Page 465, line 10. For Oh read 6b.