792 
Proceedings of the Boyal Society 
The weather was throughout clear and dry, and with the excep- 
tion of one day, April 27, which was extremely warm, the air 
temperature was low, and an easterly wind prevailed. 
Observations of Salinity. 
It is unnecessary to give in detail a description of all the sets of 
observations which were made. The following statement shows the 
range of density in the water at the places where we worked : — 
Table I . — Density at 15°*5 C. of Estuary Water. 
Tide within half an hour of 
High Water. 
Half -ebb. 
Low Water. 
Half-flood. 
Surf. 
Bott. 
Surf. 
Bott. 
Surf. 
Bott. 
Surf. 
Bott. 
Kincardine. 
27.4.86 
28.4.86 
30.4.86 
1.5.86 
1-01366 
/ 1-01666 
\ 1-01265 
1-02022 
1-02097 
1-01776 
1-00950 
1-01668 
1-00933 
1-01013 
1-01953 
1-01443 
1-01726 
1-01511 
1-01928 
1-01719 
Mean. 
Mean of 
occasional 
observa- 
tions from 
1884 to 1886 
1-01432 
1-01578 
1-01965 
1-01891 
1-00973 
1-00553 
1-01698 
1-00916 
1-01618 
1-01823 
Alloa. 
28.4.86 
29.4.86 
1-01338 
1-01010 
1-01548 
1-01530 
1-00383 
1-00464 
1-00582 
1-00818 
Mean. 
Mean of 
occasional 
observa- 
tions from 
1884 to 1886 
1-01174 
j-1-00160 
1-01539 
1-00423 
1-00700 
Cambus. 
1.5.86 
1-00367 
1-00498 
... 
1 - 
... 
This table shows that a difference of density at the surface corre- 
sponding to 0*00459, and at the bottom to 0-00267, may he expected 
between high and low water at Kincardine ; the difference between 
the density of bottom and surface water being 0-00533 at high 
water, and 0*00725 at low water. 
The decrease of density on the surface and at the bottom as the 
tide falls may vary in rate with varying conditions. The readings 
of the small hydrometer (uncorrected for temperature, which was 
practically constant throughout each series of observations) for 
several occasions are given below, and the figures in the case of 
