126 THE ROYAL SOCIETY OF CANADA 
and very deep; although, unfortunately, their actual depth is not 
known. In making the coast charts, although the height of the moun- 
tains was measured, these inlets were not sounded to the bottom. 
Judging by the best indications, the depth is probably not less than 
100 fathoms. 
In these inlets the time of high and low water at the head is very 
little later than at the mouth. This has been ascertained by simul- 
taneous records from registering tide gauges, operating day and night 
continuously for a period of several months; the time being kept 
accurately at the mouth and head by the use of chronometers. The 
results for three inlets are as follows:— 
Long Inlets. (Average Spring range, 14 ft.) | Ey Wi. L. W. 
From Lund to the head of Bute inlet: distance 66 miles. | 
From 80 simultaneous observations.............. | 7m. later. 14m. later. 
From Namu to Bella Coola, by Burke channel and Ben-| 
tinck arm: distance 69 miles. From 144 simultaneous 
DDSCEVARIONS Hu Sees Be bw eee A os Wey ROR be 2m. later. 7m. later. 
From Hartley bay in Wright sound to Kitimat, by 
Douglas channel: distance 49 miles. From 222) 
simultaneous observations <7... 6.6. eee ves | 4m. later. 4m. later. 
The range of the tide at the head of these inlets is only from 2 to 12 per 
cent. greater than at their mouth. 
It thus appears that the whole surface of the inlet rises and falls 
simultaneously, in correspondence with the impulse at its mouth given 
by the rise and fall of the tide in the open. It is also observed that 
there is little current except in the mouth of the inlet, where the pulsa- 
tion takes place. 
This action of the tide may best be exemplified by supposing a 
long and deep trough in which the water is retained by a movable end. 
If the end, consisting of a sliding partition or dam, is pushed in and 
drawn back slowly, the whole surface of the water will rise and fall 
simultaneously; and there will be no appreciable current, relatively 
to the sides, except near the movable end itself. The action of the 
tide of the outside ocean at the mouth of these deep inlets must be 
very similar to this. The rising tide creates an impulse at the mouth 
which pushes the water in at the end only. The volume required to 
raise the level 15 feet in height over the area of an inlet 60 miles long, 
half a mile wide, and 100 fathoms deep, corresponds with an inthrust 
of only 24 miles in length at the mouth. This inthrust and recession 
