of the Fishery Board for Scotland. 



433 



Instead of the gradual increase in depth from the coast line outwards 

 characteristic of the east coast of Scotland generally, depths far greater 

 than any off the east coast of Scotland are frequently to be met with close 

 in to land.'* Accordingly the range of temperature from surface to bottom 

 was also very considerable and all the greater from the fact of the rela- 

 tively higher surface temperatures frequently met with. At Station 

 XXIX., in Hielte Fiord, the temperature at the surface was 54° '0 F. 

 (12° "2 C), and at the bottom, at a depth of 135 fathoms, only 43° F. 

 (6°*1 C); while in By Fiord the surface temperature was55 0, 2 F. (1 2° '9 C), 

 and the bottom temperature at a depth of 160 fathoms, 44° F. (6 0- 7 C). 



Through the courtesy of Mr Buch, Inspector of Fisheries at Bergen, we 

 were able to visit a very remarkable natural pond or small lake in the 

 Island of Tysnbs (Station XXXI,). The distribution of temperature in this 

 little patch of water, the depth of which nowhere exceeds 15 feet, is truly 

 phenomenal. 



The temperature at the surface on the occasion of our visit was in no 

 way remarkable, being 54°'7 F. (12 o, 0 C.) ; but at 1 foot below the surface 

 it rose to 60° F. ; 4 feet down the temperature was 09 o, 2, 7 feet down 73 o, 0 

 (22°*8 C), the maximum temperature, 74 o, 0 F. (23°\35 C), being reached 

 at 10 feet below the surface. 



Further down the temperature fell very distinctly, being only 72° F. at 

 the bottom. Mr Buch informed me that careful search had been made for 

 a hot spring, but that nothing of the kind could be found and that the con- 

 clusion come to was that the whole was due to solar radiation. In support 

 of this I may point out that the specific gravity in situ of the intermediate 

 and hottest layer lies between that of the surface and bottom layers (see 

 Table I.). This must tend to prevent convection currents and therefore 

 to greatly prolong the cooling of the intermediate layer. 



Formerly the only communication with the salt water of the fiord was 

 at high spring tides, but arrangements have been made which permit of 

 the regulation of the inflow of salt water. The salt water admitted inter- 

 mittently forms the bottom layer, the very thin surface layer is formed by 

 fresh water from a small stream flowing in at the one end of the pond and 

 overflowing at the other into a short watercourse leading to the fiord. 

 It is therefore constantly renewed. The intermediate layer is formed in 

 all probability by very slow mixing of the bottom and surface layers. On 

 June 30, 1888, the maximum temperature was no less than 81°*3 F. 

 (27°'4 C.) at about 7 feet below the surface, but fell to 78°'8 F. 

 (26° C.) by the 21st of July, being then between 9 and 10 feet below the 

 surface. On August 11th the maximum temperature was 73°'9 F. 

 (24'4° C.) at about 11 feet below the surface. 



The whole matter is one of very great interest, practical as well as 

 scientific. For some years back this pond has been used as an oyster 

 nursery with great success. Large bundles of twigs or small branches 

 from neighbouring trees are suspended in the warm water by means of 

 stout wire ropes stretching from bank to bank across the pond. To these 

 the spat attaches and favoured by the high temperature develops, so Mr 

 Buch informed me, with remarkable rapidity and with a degree of 

 regularity from year to year which altogether surpasses anything 

 attained hitherto in the fiord waters outside. At a certain stage 

 of growth the young oysters are transferred to beds in the outside 

 waters. Samples of water were collected from the pond at different 

 depths and specimens of the oysters in various stages of growth as found 

 on the occasion of our visit were kindly given by Mr Buch. We also had 

 an opportunity of judging of the quality of the oysters growing in the 

 * This could not be indicated on the chart (PI. x.). 



