HUMPHREY LLOYD, D. D., D. C. L.;

=

PROVOST OF TRINITY COLLEGE, DUBLIN,

AND FORMERLY PROFESSOR OF NATURAL PHILOSOPHY IN THE UNIVERSITY.

17253

DUBLIN:

PRINTED AT THE UNIVERSITY PRESS,

BY M. H. GILL.

ADVERTISEMENT

TO THE SECOND EDITION.

THE former edition of this little work was given to
the public in the shape of Lectures, as delivered, in
compliance with the regulations of the Chair which
the author then occupied, and without any expecta-
tion that its use would extend much beyond the circle
of his immediate hearers. It has however found its
way elsewhere; and the author has been urged, by
some of his fellow-labourers in other Universities, to
reprint it. With this request he could not but com-
ply;
and he trusts that the delay in acceding to it
may be excused to those who made it, by the desire
of the author to render the work more deserving of
their favourable estimation.

In the present edition some account is given of the more important discoveries in Physical Optics, which have been made since the publication of the former. In preparing these additions, the author has derived much aid from the Répertoire d'Optique Moderne of the Abbè Moigno,-a work which contains