of Edinburgh , Session 1885—86. 793 
April 27, at Kincardine, are represented in the form of a curve in 
Plate XXVIII. fig. 2. 
Table II. gives particulars of a complete ebb and part of a flood 
at Kincardine, and of an ebb and the end of flood and beginning 
of ebb at Alloa : — 
Table II . — Tidal Variation of Salinity. 
Kincardine, 27.4.86 
Kincardine, 1.5.86 
Alloa, 28.4.86 
Alloa, 29.4.86 
Density. 
Density. 
Density. 
Density. 
Hour. 
Hour. 
Hour. 
Hour. 
Surf. 
Bott. 
Surf. 
Bott. 
Surf. 
Bott. 
Surf. 
Bott. 
10.30* 
1-013 
1-022 
11 
1-0135 
7** 
l-oio 
1-0145 
1L45+ 
1-016 
1-020 
ii‘ 
1-014 
1-0175 
11.15 
1-0115 
7.30J 
1-010 
12 
1-0165 
1-019 
11.15 
1-014 
1-017 
11.30 
1-009 
1-020 
8 
1-010 
12.30 
1-014 
1-018 
11.30 
1-013 
1-017 
12 
1-008 
8.30 
1-011 
1-017 
12.45 
1-013 
12 
1-014 
1-0175 
12.15 
1-008 
9 
1-012 
13 
1-0125 
1-0155 
12.30§ 
1-013 
1-018 
12.30 
1-009 
1-017 
9.30 
1-015 
1-018 
14 
1-010 
1-0115 
13 
1-012 
13 
1-0085 
10 
1-0155 
1019 
14.30 
1-009 
1-010 
13.30 
1-017 
13.15 
1-010 
11.30 
1-018 
1-019 
14.45 
1-007 
1-010 
14 
1-012 
14 
1-0105 
1-0185 
15. 
1-0065 
1-0095 
14.15 
1-010 
1-015 
14.15 
1011 
15.30 
1-005 
1 -0065 
14.30 
1-009 
14.30 
1-010 
1-018 
16 
1-005 
1-006 
14.45 
1-009 
1-013 
15 
1-009 
... 
15 
1-008 
1-012 
15.15 
1-0095 
1-020 
15.30 
1-0095 
1-020 
16.15H 
1-009 
1-021 
17.15 
1-009 
1-021 
* High water at 10. t High water, llh. 15m. f Low water, 71i. 25m. 
§ High water, 12h. 20m. II Low water at 16h. 20m. 
At a given time the vertical distribution of salinity in the water 
was found to be determined by the depth, position, and state of 
tide. At Alloa, for instance, the difference between bottom and 
surface water was so slight, and the depth so small, that the hydro- 
meter employed was of little use in tracing the form of the density 
curve. 
As the tide fell the water got fresher uniformly and gradually, 
the rate of freshening at surface and bottom being practically 
the same until about half-ebb, when the surface showed signs of 
more rapid dilution ; but before low water the slight and uniform 
change was re-established. If the ebb continued long enough at 
Alloa to let the level of the water fall from 2 to 3 feet below 
the ordinary low-water mark, our observations indicated that it 
would be entirely fresh in ordinary weather. In times of flood, of 
course, fresh water is found even farther down the estuary. The 
