830 PROFESSOR CHRYSTAL AND MR E. MACLAGAN-WEDDERBURN 
x dx Ron Sh Mean /h | 1/mean /h | da/ J/h 
0:00 
0:20 ‘20 57 755 377 2653 ‘0531 
1:00 80 125 11-18 9°37 1067 0854 
2:00 1:00 177 13°30 12°26 0816 0816 
3°00 1:00 231 15:20 14:25 0702 "0702 
4:00 | 1:00 231 15:20 15:20 ‘0658 0658 
5:00 | 1:00 255 15°97 1558 0642 0642 
6:00 1-00 273 16°52 16:24 0616 0616 
7:00 1:00 279 16:70 16°61 0602 0602 
8:00 1:00 279 16°70 16°70 0599 0599 
9:00 1:00 273 16°52 16°61 0602 0602 
10:00 | 1:00 258 16:06 16°29 0614 0614 
11:00 1:00 246 15°68 15°87 0630 0630 
12-00 1:00 246 15°68 15°68 0638 0638 
13:00 1:00 243 15°59 15°64 0639 0639 
14:00 1:00 222 14°90 15°25 0656 0656 
15:00 |- 1:00 207 14°39 14:64 0683 0683 
16:00 1:00 172 13-11 13°75 0727 0727 
16°54 D4 163 Lari 12°94 “O73 0417 
17°32 ‘78 127 11:27 12°02 0832 ‘0649 
18:04 oN esis) 11°62 11°45 0873 0629 
18°70 66 45 6-70 9°16 1092 0721 
19°45 ‘75 13 3°61 516 "1938 1454 
19°84 39 0 0:00 181 D525 2155 
17234 
Hence al, = 3520 x 1°7234/,/32°2 = 1069” = 17°82’. 
Therefore PANS = Sol, 
I, = 5-94’. 
The periods given by Du Boys’ rule are therefore all greater than those deduced 
from the Hydrodynamical Theory ; but the divergence gets less as the nodality rises, 
the deviations for 7T,, zI,, .T3 being 23 per cent., 9°4 per cent., and 3°5 per cent. 
respectively. 
Nopes or Locu Harn. 
§ 11. It appears from H.T.S. §§ 39 and 42 that we may calculate the values of 
w corresponding to the nodes by means of the equations :— 
$(w)=S'(c, w) K(e, 1)-C(e, w)=0.. : : ; é (9), 
d(w)=S(c', w) K(c’, 1)-C(e, w)=0 . : : : - * (Ol 
or (Le) Oe ‘ , , ; : : : (11), 
WG, Aas , é é F 3 ; » Uy 
where w denotes the scalar value of v/a or v/a’ in all cases; z=(1—w)/2; and we 
use (9) or (10) and (11) or (12) according as we are looking for nodes on the shallower 
or on the deeper side of the deepest normal point of the lake. 
