98 Mr W.N. Shaw, Some Laboratory Notes. [May 30, 
6 (ti) = cos (218 n't pt © 1B pt x) 
dh? 
d (uw) = cos (2h! h’? p2 a a) 
Cee 
3 d? . 4 
= "8 8 pt i: 
im (@) = cos (28 ane p22 ls 
and 
= COs 
seal 
a(n iy de 1 +4NW RS) Be 
yen Ba oF 
) 
d (u) = 008 |(R, + 41VR a) 
#0 eae 
n (w) =cos |(% +4 RT) a vie 
In the last group & denotes p’, so that 
pee 
T° 
In s’(w) the accent denotes differentiation with respect to w; 
the expressions for s’(w) have been given in preference to those for 
s (w) as they are analogous in form to those of the functions ¢ (w), 
d(u),n(u). The formulee for s (w) may be at once obtained by in- 
tegration with respect to 2 Taking the last group, for example, 
we have 
dy) 
ae sin |(Z Bak Be + MRS) x) 
P r 
(7, 41D a TP +4hn RS) 
(2) Some Laboratory Notes. By W. N. SHaw, M.A. 
The author exhibited the following experiments: 
1. Resolving power of a telescope. 
The arrangement was a modification of that described by Lord 
Rayleigh (Phil. Mag. August 1880). Instead of a diaphragm 
with unalterable aperture an ordinary adjustable slit such as is 
used for the projection of a spectrum was mounted imme- 
