422 SEVENTH REPORT—1837. 
instructed to afford every facility and assistance in his power ; 
a most accurate survey of the river, with a longitudinal section 
and accurate transverse sections at every half mile were obtained, 
and a geometrical Jevel of 18 miles was laid down with great 
precision. On this line were erected tide gauges of a peculiar 
construction, on which a small fraction of an inch could be read 
with ease even in a rough sea, and at a considerable distance 
from the instrument. These were placed at nine stations, and 
were simultaneously observed by careful observers every five 
minutes during at least one tide each day. The form and velo- 
city of each tide wave were thus ascertained with the desired 
accuracy. Application was at the same time made to Captain 
Denham, a well-known member of this Association, who was 
kind enough to cause such observations of the corresponding high 
waters at the Liverpool Docks to be made as the nature of the 
situation would afford ; and these, although less perfect than they 
would have been had the new arrangements for that purpose 
been completed which the interest taken by the British Asso- 
ciation has been the means of originating, were yet sufficient to 
enable us to determine the tidal interval of the ports in the 
Clyde with Liverpool more accurately than hitherto. The 
observations after laborious corrections and reductions were all 
referred to mean solar line on the meridian of the observatory of 
the University of Glasgow, kindly granted by Professor Nicol 
for the purpose of regulating the chronometers. 
The waves of the sea formed the subject of careful attention to 
your Committee. For this purpose one of them obtained the use 
of the Mermaid yacht, of Mr. Bogle, of Glasgow, kindly granted 
at the request of Mr. Allan, the secretary of the Northern yacht 
squadron, for the purpose of making the necessary observations 
at sea. The weather was rather unfavourable. The vessel en- 
countered alternately severe gales and dead calms, which first 
drove her to seek shelter and then prevented her from leaving her 
asylum. By means however of these observations, and of others 
made in steam vessels crossing the Irish Channel, the results 
aimed at were obtained. ‘This series was afterwards completed 
by observations made on the sea shore, by which the pheno- 
mena of surges have been perfectly explained. 
The series was concluded by observations made in experi- 
mental reservoirs and channels. These were constructed of a 
variety of forms. The waves were generated in different ways 
and of very different species. An apparatus was contrived by 
which very great accuracy was obtained in the determination 
of velocity. A considerable series of these observations are 
given at the end of this report exactly as they were made, and 
