April 9, 1885] 



NA TURE 



543 



1S7-1 1 n the River Plate, in the same way as Dr. Mac- 

 adam on the Clyde. Mr. F. Newman has kindly supplied 

 a translation of Kyle's Spanish pamphlet ("Algunos Datos 

 sobre la Composicion de las Aguas del Rio de la Plata"), 

 and a chart of the Plate, with the water-sampling stations. The 

 results brought out by Prof. Kyle are interesting, but, like the 

 other observers cited above, he neglects to mention whether 

 his specific gravities are reduced to 0°, to 4°, or to I5°'56, or 

 whether water at o', 4°, or I5°'56 was taken as unity. It is 

 therefore impossible to consider the results except as purely 

 relative to the estuary in question, and no comparison between 

 the different investigators can be made. 



The Cattegat, Skagerrack, Baltic, and north-eastern parts 

 of the North Sea have been made the subject of very careful and 

 prolonged examination by various Danish and German scientific 

 workers. Water-samples have been taken regularly for a num- 

 ber of years at various points along the coast, and from light- 

 [ light-ships at considerable distances from land. The 

 results of the examination of these samples from 18; 

 are tabulated in conjunction with the meteorological conditions, 

 especially with respect to rainfall, in a recently issued paper by 

 the Commission in Kiel for the scientific investigation of the 

 German seas, : The general low densities of these waters, and the 

 variations to which they are subject, make the conditions which 

 obtain there no', unlike those in an estuary. 



it is fully realised that it will take years of consecutive 

 observations to thoroughly settle the relations of the fresh and 

 salt water in an estuary, and that many conditions, such as the 

 currents, law of the tides, and rainfall over the area drained by 

 ipal river and its tributaries must be taken into 

 account ; it is considered expedient to state the results observed 

 in the six months, from June to December, 1SS4, on the Firth 

 of Forth. i 1 ilts are purely preliminary ; but as little 



attention has been given such matters hitherto, they may prove 

 . and may lead to suggestions for improvements in 

 carrying on the work. 



i ih of Forth. — The River Forth rises in the valley 

 I len Lomond and Ben Venue, is joined near Stirling by 

 the Teith, and gradually merges into the Firth of Forth, the 

 lint where the river ends and the Firth begins being a 

 matter which permits of difference of opinion. Probably the 

 best plan is to view the river as ending at Queensferry, but for con- 

 venience the term " Firth of Forth " may be applied as describing 

 the river and Firth proper from Alloa to the Isle of May, a 

 distance of fifty-five miles. According to Keith Johnstone the 

 area drained by the Forth is 500 square miles. Few 1 

 flow into the Firth. Those of any importance are : on the north 

 side, the Black Devon, at Clackmannan ; and the Leven, at Leven : 

 on the south side there are the Carron, at Grangemouth ; the 

 Avon, a few miles further east ; the Almond, at Cramond ; the 

 at Leith ; the Esk, at Musselburgh; and the 

 Tync. near I >unbar. 

 From Alloa to within three miles of Queensferry the depth 

 under 10 fathoms ; there it increases, at first 

 gradually, then at the Bamer Beacon abruptly, to over 50 fathoms, 

 1 , to over 40 tathoms. This is the deepest 



Firth, and the narrowest. The Forth i 



iction at this point. Avery strong tide runs 

 in the channels on each side of Inchgarvie, and the deep water is 

 to a very small area. The IO-fathom stream runs 

 ■ 1 D -hole, until off Kirkcaldy, when- it widens 

 out in a funnel shape, and approaches the shore on each side. 

 There is a short tract over 10 fathoms to the south of Inchkeith, 

 known as th vera] small depression 



than 20 fathoms occur between Queensferry and Inchkeith, and 

 a little to the east of that island the 20-fathom area begins as a 

 narrow stn *, ird, and spreading oiu 1 



I I is connected to the mainland of Fife 



; lan 20 fathoms from the surface; 



and, about four miles east of the May, depths beyond 30 fathoms 

 commence. 



Ba to Largo divides the Firth 



ly different halves. To the west of it th 



' ml the depth slight ; to the east 



of il the shore slopes down abruptly, and the bed of the Firth is, 



insignificant exceptions, uniformly over 20 



fathoms in depth. 



Ben : cht— fur die Jahre 1S77 «/s i3Si. Berlin, i82 4 : •' Period- 

 ische Schwankungen dcs Salzgehaltes lm OlwrflSchenwasser in dcr Ostsee 

 und Nordsee." 



Observations on the Surface Salinity in the Firth. — It is 

 assumed that the amount of total salts may be deduced from the 

 density, as if estuary water were ocean water diluted with pure 

 water. This cannot he exactly the case, as the salts carried down 

 by rivers are in quite different proportion to those found in the sea, 

 and before the processes occurring there have had time to pro- 

 duce uniformity of composition — that is, where river-water pre- 

 dominates — the proportion of salts among themselves must vary. 

 Consequently, until exact experiments can be made on this 

 point, the interpretation of estuary densities by ocean-water 

 tables must be taken with reservation, and it is better to view 

 the densities as such, without reducing them to amounts of total 

 salts. To get a preliminary view of the rate of freshening, it 

 was determined in September 1SS4 to make a monthly trip for 

 collecting water samples from the entire Firth ; and on Septem- 

 ber iS the Medusa proceeded from Inchkeith to Grangemouth 

 for that purpose. Surface samples were taken every five miles, 

 and bottom samples at each alternate station. Observations 

 were made both in going and in returning. The intention to 

 make the complete tour of the Firth in one day had to be relin- 

 quished, and the Inchkeith to May section was completed on the 

 25th. This double trip showed that the densities of the water 

 samples decreased steadily, gradually, and uniformly from the May 

 to Inchkeith, but that the change then became more rapid, the 

 curve resembling a portion of a rectangular hyperbola. The 

 second water sampling trip was on October 7 and 8 ; the water, 

 beautifully clear and transparent, and of a deep green-blue 

 colour at the May, became light green and less transparent about 

 Inchkeith, and from Inchgarvie onwards it was yellow and very 

 muddy. The results were similar to those of September. The 

 November trip took place on the 10th and nth; the weather 

 was fine, almost summer-like, and, in consequence of previous 

 heavy rains, all the rivers were in flood. The effect was a 

 marked lowering of the density of theism-face water, greatest in 

 the upper reaches of the Firth, but quite perceptible at the Isle 

 of May, which is almost in the open sea. The effect of this 

 was to reduce the density at Inchgarvie from its mean 

 of 1 '02382 to 1 '02029 ; that at the Oxcar Beacon from the mean 

 of 1 0243S to I'o2022; that at Inchkeith from 1 '02472 to 

 I 02403 ; and those at Stations VIII. and IX. from i"02505 and 

 I '0251s to 1 '02458 and i'025oS respectively. The December 

 trip did not take place till the 25th, when my friend Mr. Ritchie 

 was good enough to take charge of the eastern excursion. The 

 day was tine, with a north-easterly breeze and a slight swell. On 

 the 27'ih the yacht started for Alloa, but the morning, which was 

 hazy, gave place to a day of fog, and it was impossible to pro- 

 ceed beyond Inchgarvie. The 29th and 30th were also misty, 

 and this portion of the trip had very reluctantly to be dispensed 

 with. 



The effect of the tide obscures the changes of salinity to a 

 certain extent in these monthly cruises, but, although the data 

 are so few, they are sufficient to show that between Inchkeith 

 and the Isle of May — that is, in the wide and open part of the 

 Firth — the tidal effect is relatively slight and the variations in 

 density very gradual, though perceptible ; while from Inchkeith 

 to Alloa the tidal effect increases with every mile, and the rate 

 of change becomes more and more rapid. The following tables 

 (I. and II.) give the figures observed in these consecutive 

 trips : — 



Table I. — Density at I5°'s6 

 1884 I. II. lit. " IV. v. VI. 



Sept. ... — ... — ... 1*02082 ... i'o2285 ... 1*02444 ... I'02470 

 Oct. ... i'ooi6o ... i'oio88 ... 1*01911 ... i'02272 ... fo2332 ... i'o2443 



NOV. ... 099O23 ... I"00272 ... X'OI4X9 ... 1*01704 ... 1*01946 ... 1*02022 



Dec. ... — ... — ... — ... — ... 1 02351 ... 1*02353 



1884 VII. VIII. IX. X. XI. XII. 



Sept. ... 102499 ... 102533 ... 1*0253! ... 1 , ... 102555 



Oct. ... 1 1 ... 102547 — 1025-5 ••■ 1*02555 — 1*02558 



Nov. ... 1 '02403 ... 102458 ... i'o25oi ... 1*02529 ... — ... — 



Dec. ... 1*02464 ... 1*02511 ... 1*02508 ... 102545 ••■ 1*02554 ... — 



Tai-le [I.— Alkalinity 



1884 



Sept. 



Oct. 



Dec. 



The me 



vn. vnr. 



49*6 .... — 



. 48 '3 ... 48-6 

 . 51-2 .. 

 » of the G..: 



