Mathematical tracts on the lunar and planetary theories, the figure of the earth, precession and nutation, the calculus of variations, and the undulatory theory of optics.

WIRE GRATING PLACED BEFORE A LENS. 313
Let B - -b = C: then the whole displacement at M
bX
{restoring the factor froi (80)} is
2wq
X2b. 27rqf. 7rpe. r p (e + g)
sin. sin - sin vt - C + n}.
rr2p q X b Xb X b
The finite integral of the last term with respect to n is
-1 2wr p(e+g)..cos c -- {vt -C c+. (n -)},
p (e + g)w
sin
bX
which from n = o to n = mn is
sin mp (e + g) r
~~ssin - C
bX p t ~p(e +g) - i
we have for the whole dsin vt - C +
sin p (e + g) 7 ( b 2.sinl-l Slf - p. sin-(v t- D):
w2zpq )b )b sinP (e + g. Xb X
b)
Thus, putting
sin mp (e + g) *r
rp q Âb X b. p (e +- g) (r X
Sin
bX
and consequeiitly the intensity of the light is
p P(e+g)7r I2
4 ef Y2srin Àb \7rp ie Xb. P(e +g) 7r
84. The most remarkable variation of this depends on
the last term. Ths sin r b 2
the last term. This may be represented by k i where
' - ' \ ~~~sin 0I