476 
Proceedings of the Boy al Society 
XV. On 20th August observations made at Portessie, 6 miles 
east from the Spey, showed at 9 h .50 a density of 1*026, at ll h .5 of 
1*026, and at 18 h .15 of 1*027. 
The Salinity of Spey Bay. 
The mean density at 15° *56 C. of the bottom water in Spey Bay 
was found to be 1*02567. It varied in twelve cases from 1*02540 
to 1*02598, while the surface water varied in density from 1*02000 
to 1*02576. The observations made seem to warrant the conclusion 
that the water is, as a whole, of a density slightly greater than 
1*02550 in Spey Bay, and considerably greater in the centre of the 
Moray Pirth. Whether the slight reduction in density is due to 
the action of the Spey water, or to the vicinity of the Cromarty 
and Inverness Births, can hardly be said, and it is unimportant in 
connection with the immediate subject of which we treat. 
The Spey water runs rapidly out of its comparatively shallow 
channel : at low tide, partly on account of its shallowness, and at 
high tide, partly on account of the bar, it flows across the surface of 
the sea water in a thin stream, freshening to a marked extent only 
the upper few feet, and spreading out laterally in the form of a fan. 
The exact shape and direction of this expansion are dependent on 
the volume of the river, on the state of the tide, on the confor- 
mation of the mouth, which is subject to incessant change, and on 
the direction of the wind. The usual trend of the river current in 
the bay appears to be north-easterly. 
The observations VIII. (p. 472) show that when the boat sailed 
due north, the density at f mile from the river mouth was 1*02557 
on the surface, strong sea water] while those under IXa., with the 
river in the same state as regards flood, show no clear indication of 
the course of the stream on the circumference of a circle 3 miles in 
radius described from the mouth of the Spey. The pocket hydro- 
meter readings, 1X6., show that when \ mile off shore the stream 
was clearly defined, its margin shading off gradually on the eastern 
side and abruptly on the western, where the transition from 
brackish to salt water was very sharp. The stiff breeze which was 
blowing from the S.S.W. would help to carry the stream to the 
N.N.E., and it might have been narrow enough to pass between 
two of the observing points and so elude detection. 
