of the Fishery Board for Scotland, 
359 
surface ; ami the comparative immunity from rapid and great changes 
of salinity appears to point to the peculiar adaptability of the section 
of the Firth of Forth, bt tvveeu it and Inchkeith, for the cultivation 
of oysters. Whether the practical extinction of the oyster-fishery on 
the Middle Bank is due to some slow change in the physical conditions 
of the water or not, might possibly be ascertained if there existed any 
early records of specific gravity observations. 
North, Carr Light-vessel. — This vessel is anchored in 24 fathoms 
of water off the North Carr Rock, near Fife Ness, at the entrance 
to the Firth of Forth, and on the southern boider of St Andrews 
Bay. A better situation for physical observations, to throw light on 
the conditions of the sea on the east coast of Scotland, could not be 
desired. Observations of temperature were made at 9 a.m. and 3 p.m. 
from November 1889 onward, at the surface, 12 fathoms, and the 
bottom; observations at 6 fathoms were also made for some time, 
but discarded as unnecessary on account of the small vertical range 
of temj)erature. Negretti and Zambra's deep-sea thermometers were 
employed in a special frame designed by Dr T. Wemyss Fulton, which 
admits of the use of a weight to invert the instrument and cause it to 
register. The air temperature was also noted. 
The mean temperature of the surface water for 1890 was 8° '9 at 9 a.m., 
and 9°"0 at 3 p.m., this being a higher temperature and a lower 
range than occurs at Oxcar. At the bottom, the mean temperature for 
the year was 8° '7 at 9 a.m., and 8° "9 at 3 p.m., showing a slightly 
lower temperature and less range than on the surface. The means 
for the first three mouths of 1891 were the same at both surface and 
bottom, viz. : — 5°*2 at 9 a.m., and 5°'3 at 3 p.m. 
The highest temperature on the surface was 14°'0 on September 12, 
1890, at 3 P.M., the lowest r-3 on March 17, 1891, at 9 a.m. ] 
readings of 4° '7 and 4° '8 occurred once in December 1889 and March 
1890. At the bottom, the highest temperature recorded was 13° '5 on 
September 9 and 13, 1890, at 3 p.m., the lowest 4° '4 on March 8 
and 10, 1890, at 9 a.m. ; but 4° '5 was noted on several occasions. 
The extreme range was thus 9°'7 on the surface contrasted with 11°*4 
at Oxcar. The range of temperature at the bottom was 9°'0. 
Table III., gives the entire set of means in ten-day periods, and Table 
IV. the monthly means. The 9 a.m. surface temperatures from this table 
are shown graphically in comparison with those of the other stations in 
Diagram IV. (Plate XVII.). Observations taken at 12 fathoms at this 
station are unsatisfactory ; the thermometer used at that depth appeared 
to be sluggish in action, and so read higher in summer and lower in winter 
than those at the surface and bottom ; the record of the two latter may 
be considered more trustworthy. The results would be more normal, and 
several peculiarities in the annual change of temperature would disappear 
if we assumed that the temperatures at surface and at 12 fathoms had 
been entered in the wrong columns in the book ; but after questioning 
the observers and examining the record, I can see no other grounds for 
supposing that this could have been done. 
The curve of seasonal change of temperature in Diagram IV. is remark- 
ably regular with two exceptions. The readings for February and March 
1890 seem to be too high, not showing a distinct minimum, and the low 
temperature of August is a peculiar break in the uniform rise which the 
other two east coast stations (Oxcar excluded) show to have taken place 
between May and September. With these exceptions, the curve for the 
Carr Rock lies intermediate between those for Abertay and the Bell Rock, 
exactly as might be looked for. 
The average difference between surface and bottom temperature was 
