of Edinburgh, Session 1885-86. 
485 
enables its progress through the Firth to he traced as a dark hand 
to a distance of more than 6 miles. The shore water appears to he 
freshened by water percolating through the shingle beaches from 
the river. 
Alkalinity and temperature observations are described and dis- 
cussed. 
In conclusion, a classification of river entrances into three groups 
is put forward tentatively. The Spey typifies a large river entering 
a tidal sea directly across a bar ; the Tay, a large river, entering by 
a short, narrow, shallow, barred estuary ; and the Forth, a small 
river, merging into a long, wide, deep, and open firth. 
7. The Distribution and Significance of Micro-Organisms 
in Water. By A. Wynter Blyth. 
The results of more than a year’s study of the distribution of 
micro-organisms, that is* bacteria and fungi in water, are I think of 
sufficient interest to justify a short communication. 
Methods . — -The micro-organisms in water being for the most part 
jn the form of isolated spores or seeds so small as to be practically 
invisible, the first step was to make them visible by “cultiva- 
tion.” This cultivation took place in nutrient gelatin, according to 
principles too well known to require description. I will, therefore, 
confine my remarks merely to the details of certain special modifi- 
cations of the ordinary process which I adopt. 
The cultivation takes place on glass plates 4 inches x 4 inches; on 
to these plates are cemented glass rings \ inch broad, J inch deep, and 
3*8 inches in diameter, thus forming large shallow cells. The method 
of cementing the rings on to the plates is novel ; both are sterilised 
at a high temperature in a hot-air oven, and while still hot drops 
of the nutrient gelatin are placed on the ground surface of the ring, 
the ring is then applied to the plate, rotated, and put under a dust- 
proof shade to cool and set. 
The water to be examined is weighed in a special form of drop- 
bottle (see fig. 1). A drop is then dropped on the plate by the aid of 
the pipette stopper, and the bottle reweighed so as to obtain by 
