8 SEVENTH REPORT—1837. 
vations sufficiently numerous to warrant him to draw any general in- 
ference, but simply remarked, that in January there were twenty-six 
of the evening tides higher than those of the morning, in February 
nineteen, in March twenty-four, in April twenty-four, and in May 
nineteen. In June the morning tides began to take precedence in 
point of height, there being in that month eighteen morning tides 
higher than those of the evening, in July twenty-one, and in August 
twenty-four. So far as the observations went, there did not appear to 
be any connection between the height of the tides and the pressure 
of the atmosphere, as indicated by the barometer. 
The observations on the tides at Glasgow were continued by Mr. 
Mackie for five months, though these months were not continuous. 
From these observations he deduces the “vulgar establishment” at 
that place to be 1 hour 43 minutes, and the “ corrected establishment” 
1 hour 9 minutes. With regard to the intervals between the meridian 
passage of the moon and the time of high water, although they are 
greatest about new and full moon, and decrease till about the seventh 
and eighth days after these periods, they are subject to very great irregu- 
larities ; to such an extent is this case, that he had not been able to 
extract from the five months’ observations a regular curve for the 
semi-menstrual inequality. In the former diagram the light dotted 
line represents the genuine curve obtained from the five months’ 
observations: it is probable that, when fully determined, it will run 
a little below that for London for the four or five first intervals after 
new moon, gradually, however, approaching, till it coincides nearly 
for the sixth, seventh, eighth, and ninth intervals, when it will again 
gradually diverge and terminate somewhat below that for London. 
The river Clyde has undergone very great alterations in its channel, 
even within the last fifty years; and as it is of the utmost importance 
to have a record of the influence produced on the progress of the tide, 
by alterations in the breadth, depth, and form of the channel of a 
river, the following brief detail of the modifications in the channel of 
the Clyde, and the effects which have ensued, may serve as a precedent 
in directing, so far, those who are entrusted with the improvement of 
the navigation in other rivers. About the commencement of the 
sixteenth century the river was entirely in a state of nature. Its 
banks were in general flat and low. The channel abounded with 
shoals and fords, at some of which the tide, at high water, was not 
above 3 feet, and at low water about 14 feet. The lowness of the 
banks permitted the tide to spread over a great extent of surface, 
forming pools and islands, among which the most experienced skippers 
could not always distinguish the real channel. In this state the cele- 
brated engineer Smeaton found the river, when solicited by the 
magistracy to report upon the best method of improving it, in 1755. 
At this period the breadth varied greatly from Glasgow to Bowling 
Bay, a distance of about ten miles. The breadth at Glasgow, imme- 
diately below the Broomielaw, was about 500 feet; and although, fur- 
ther down, it was in some places less, it upon the whole increased, 
