S68 
Part III. — Ninth Annual Report 
the very much greater specific gravity of the bottom water at low water 
neaps, the ebb affecting only the surface layers. During spring tides, 
with the stronger ebb, the freshening effect of the river water is carried 
down to the bottom. 
It is impossible in a report of this nature to enter exhaustively into all 
the interesting questions which are suggested by the records of tempera- 
ture and specific gravity taken at Abertay. The summaries of ten-day 
means. Tables I. and XIV., and of monthly means. Tables 11. and XV., 
published in this Report will repay study, and the bulky record of the 
individual observations remains available for more detailed discussion if a 
suitable occasion should offer. 
'Garland' Trawling Stations in Firth of Forth. 
Table IX. presents in a concise form the observations made on the 
* Garland ' in the course of regular monthly trips in which each of the 
trawling stations marked on the map (Plate XVI.) were visited. The 
observations were made at each end of the station, and of course at 
various hours. They possess special value on account of being made by 
experienced observers, and if continued for some years they will be of the 
utmost service in determining the regular seasonal variations of tempera- 
ture over the fishing grounds. The time at disposal for drawing up the 
present Report prevents me from dealing so fully with this part of the 
work as I should have liked, but in many ways the detailed consideration 
of the figures will come most appropriately in connection with the work 
done on the ' Jackal ' and ' Vigilant ' on different parts of the coast. 
One feature of these observations is however so novel and interesting 
that it may be referred to here in^some detail. This is the measurement 
of transparency. Transparency of the water is measured by sinking a 
white enamelled disc about 3 feet in diameter until it just ceases to be 
visible. The depth of visibility depends partly on the amount of sun- 
light, which varies with the altitude of the sun, and on the amount of 
suspended matter in the water. Part of the suspended matter is composed 
of mud particles and sediment of various kinds carried in by rivers, and 
the fresher the water the greater is its amount. Part consists of small 
organisms such as diatoms, copepods, &c. To distinguish between these 
there are as yet no available data, but the general bearings of transparency 
come out distinctly enough. The figure for transparency is the number 
of fathoms at which the disc ceases to be distinctly visible. 
Low Sun. Half- Year. 
High Sun. 
Half- Year. 
o 
Eastern End of 
Western End of 
Eastern End of 
Western End of 
H 
m 
Station. 
Station. 
Station. 
Station. 
Max. 
Min. 
Mean. 
Max. 
Min. 
Mean. 
Max. 
Min. 
Mean. 
Max. 
Min. 
Mean. 
I. 
35 
1-5 
2-4 
3-0 
1-5 
1-9 
5-3 
1-5 
3-5 
3-5 
1-0 
2-4 
II. 
3-5 
1-5 
2-5 
3-0 
1-8 
2-5 
4-5 
1-5 
3-4 
4-6 
1-5 
3-2 
III. 
2-5 
1-5 
2-0 
3-0 
1-0 
1-9 
4-5 
1-0 
2-4 
6-5 
1-0 
2-4 
IV. 
2-0 
0-8 
1-8 
2-0 
0-8 
1-6 
3-0 
1-0 
2-0 
2-5 
1-0 
2-0 
V. 
5-0 
2-8 
37 
4-0 
3-0 
3-8 
6-5 
2-5 
4-8 
6-5 
2-3 
4-6 
VI. 
4-0 
1-5 
2-6 
40 
1-8 
2-7 
5-5 
2-5 
4-1 
5-0 
2-0 
4-1 
VII. 
4-0 
1-5 
2-7 
2-8 
1-5 
2-0 
5-0 
2-6 
3-6 
4-0 
1-5 
2-6 
VIII. 
6-0 
2-8 
4-1 
4-0 
3-0 
3-3 
8-5 
2-5 
.5-8 
5-0 
2-0 
3-8 
IX. 
6-5 
2-5 
4-4 
5-5 
3-0 
4-3 
11-5 
2-8 
6-5 
8-5 
4-5 
6-6 
Mean, 
i 
2-9 
2-6 
4-0 
3-5 
Mean of all Low Sun Transparencies 2 '8. 
„ „ High Sun „ 3-8. 
