86 MR DAVID B. MORRIS ON 
channel was diverted into a straight cut to assist navi- 
gation, with the result that the tide does not now flow 
nearly so far. A bathymetric survey of the River Forth 
would yield interesting results. The layers of fresh and 
saline water remain separate in a most peculiar way, 
and samples of water taken at different depths and at 
different conditions of the tide would furnish most in- 
structive data. This subject has been investigated by the 
staff of the Scottish Marine Station at Granton, and by the 
Fishery Board of Scotland. Those mysterious lines of 
smooth water and peculiar markings on the surface of the 
river could possibly be explained by an investigation of the 
river’s bed, in conjunction with its fantastic windings. 
The gradual change from fresh water to maritime 
conditions should be studied also in the fish and shell fish 
of the river, and the plants of the river and its banks, I 
have not noticed the sea pink (Armeria maritima) higher up 
than Longannet Point. A few years ago a seal (Phoca 
ovitulina) was killed about two miles above Stirling. 
The islands of the river and the causes of their formation 
are an interesting subject, never investigated so far as I am 
aware. Ascending the river, we find the following 
islands :—Alloa Inch, Tullibody Inch, “ Alan’s Isle” and 
Group at the delta of the Allan, and Group below Craigforth 
Mill. 
The islands at the mouth of the Allan are clearly formed 
of detritus brought down by that river. They possess an 
interest through association with Robert Louis Stevenson, 
In Kidnapped, Stevenson makes his hero write thus :—‘ In 
Allan Water, near by where it falls into the Forth, we 
found a little sandy islet, overgrown with burdock, butter- 
bur, and the like low plants, that would just cover us if we 
lay flat. Here it was we made our camp, within plain 
view of Stirling Castle, whence we could hear the drums 
beat as some part of the garrison paraded. It behoved us 
to lie close and keep silent. But the sand of the little isle 
was sunwarm, and the green plants gave us shelter for our 
heads.” The burdock and butterbur still flourish on 
“ Alan’s Isle.” 
The group of islands below Craigforth Mill number 
