350 



Appendices to Fifth Annual Report 



Berwick along the south shore across Aberlady Bay. The entire volume 

 of water between Alloa and the Isle of May, calculating from the data of 

 the Admiralty charts, is 36,700,000,000 cubic yards at low water, and about 

 5,000,000,000 cubic yards additional at high tide. The diagram, figure 1, 

 represents by means of shading the distribution of depth in the Firth of 

 Forth, the contours of 5, 10, 20, 30, and 40 fathoms being drawn. 



It is unnecessary to enter into detail as to the manner of observing 

 the physical conditions of the water, because the processes are described 

 in sufficient detail in published papers,* and they do not differ materially 

 from those employed on the trip of the ' Garland ' to the Moray Firth, 

 reported on in this volume. The vessel employed for the observations, 

 which lasted over two and a half years, was a 30-ton steam yacht, the 

 4 Medusa,' fitted with an extremely convenient derrick and steam winch, 

 by means of which the work was done very rapidly. 



Salinity Observations. — The density of water samples collected during 

 periodical trips along the centre of the Firth was determined by a 

 very delicate hydrometer, and the results reduced to their value at 

 15°'56 C. (60° F.). In Table I. the average density at high tide and low 

 tide (' high ' tide being considered between half flood and half ebb ; 

 ' low ' as between half ebb and half flood) is given, and also the 

 maximum and minimum observed during the whole time of my observa- 

 tions. For convenience in comparing with the results for other regions 

 the percentage of total dissolved salts is calculated and added in a special 

 column. The figures are given for each of twelve stations all situated in 

 mid-channel and five miles apart. Careful comparison of the north and 

 south channels at Inchkeith (Station V.) showed that at all states of the 

 tide the difference between the two was inappreciable, and of the 

 samples from which the average was taken about half were collected on 

 each side of the island. The results given in the table are represented 

 graphically in figure 2 (Plate XXI.). 



While the data for Stations III. to X. may be viewed as fairly well 

 established, more observations would be required before implicit confidence 

 could be placed on the figures for Stations I., II., XI. and XII., and on those 

 for the bottom salinity at Stations IV., VI., VIII. Considering the table 

 and curve, one sees the following state of matters to hold for the central line 

 of the Firth. The salinity of surface water increases rapidly from the river 

 to Queensferry (IV.), the difference between high and low tide being 

 considerable. From Queensferry to Inchkeith (VII.), the rate of increase 

 is more gradual, and the tidal difference is less ; while from Inchkeith to 

 the Isle of May the rate of increase in salinity is very slight, and the 

 tidal variation almost imperceptible. Two features in the curve for surface 

 salinity at low water attract attention. One, an irregularity at Station 

 VI., is due to the freshening action of the Almond, which at low tide 

 flows north across the Firth. The second anomaly is a dip in the curve 

 beyond the Isle of May. This has been shown to be due to the water of 

 the Tay sweeping through St Andrews Bay with the ebb tide, and carried 

 up the Firth of Forth as far as Anstruther by the first of flood. St 

 Andrews Bay appears, from some observations made in June 1885, f to be 

 a prolongation of the estuary of the Tay, and the salinity off St Andrews 

 to be about equal to that at Station VIII. in the Firth of Forth off 



* 'Salinity of the Firth of Forth,' Proc. Boy. Soc, Edin. xiii. pp. 29-64 ; ' Tem- 

 ' perature of Water in the Firth of Forth,' Ibid., xiii. pp. 157-167; ' Tidal Varia- 

 1 tion of Salinity and Temperature of the Estuary of the Forth,' Ibid., xiii. pp. 790- 

 799. 



t ' Note on the Salinity of the Firth of Tay and of St. Andrews Bay,' Proc. Roy. 

 Soc> Edin. xiii. pp. 347-350. 



