Tidal Phenomena at Inland Boreholes near Gradoch. 
89 
The curve A was now residuated with respect to T = 12 hrs. 32 min., 
and yielded a curve 0. This curve C was apparently composed of several 
harmonic components whose periods were very similar to each other, but 
one of these components had a considerably greater amplitude than the 
others. Attention was confined to this dominant component. By placing 
the eye near the level of the cloth at one end and glancing along the fore- 
shortened curve, I was able to count 14 crests and 14 troughs in the 
curve. 
I determined as nearly as possible the time positions of two or three 
of these turning-points near the beginning and end of the curve, and 
obtained the following results : — 
(i) From 1st L.W. to 14th L.W. a period of 311 hrs. 59 min. 
^ 311 hrs. 59 min. 
13 
= 24 hrs. 
Owing to flatness of curvature and proximity to the beginning of the 
curve, the 1st H.W. is a badly defined point. 
(ii) From 2nd H.W. to 14th H.W. is a period of 286 hrs. 17 min. 
286 hrs. 17 min. cox. - 
.-. To = ^2 = 23 hrs. 51| mm. 
Taking the mean of these two values of Tc, we get for the period of 
the dominant harmonic of curve C as a first approximation the value 
23 hrs. 56 min. 
Eeturning to the original curve A and residuating it with respect to 
T==23 hrs. 56 min., a second residual curve D was obtained. This 
curve D of course strongly resembled curve A, and, like it, showed 
26 crests and 26 troughs. That curve D contained more than one 
harmonic component, however, was obvious from the fact that the 
amplitudes were smaller near the middle of the fortnight than near 
the beginning and end. 
The times of the first and last H.W. and L.W. were determined, giving 
the following results : — 
(i) From 1st L.W. to 26th L.W. was a period of 311 hrs. 41 min. 
311 hrs. 41 min. . 
.-. Td = 25 = 12 ^^s. 24 mm. 
(ii) From 2nd L.W. to 26th L.W. was a period of 312 hrs. 0 min. 
.-. Td = = 12 hrs. 29 min. 
