Proceedings of the British Association. 333 
ports of London and Liverpool, by Mr. Lubbock. Mr. Lubbock 
stated, that through the indefatigable exertions of Mr. Dessiou, con- 
siderable progress had been made in the reduction of the observa- 
tions made at Liverpool by Mr. Hutchinson. The diurnal inequality 
or difference between the superior and inferior tide of the same day, 
which in the Thames was very inconsiderable, if not insensible, was 
found at Liverpool to amount to more than a foot; a matter upon 
which the learned gentleman laid considerable stress, as calculated 
to lead to important practical results. The object of these reduc- 
tions was to compare the results of theory with these observations, 
and with those of Mr. Jones and Mr. Russell made at the port of 
London. The principal objects of comparison were the heights of 
the several tides, and the intervals between tide and tide; and these 
were examined in their relations to the parallax and declination of the 
moon and of the sun, and in reference to local, and what may in one 
sense be called accidental causes, as storms, &c. Of this latter, one 
of the most curious, as well as important, is the effect of the pressure 
of the atmospheric column. The author stated, that M. Daussy 
had ascertained, that at the harbor of Brest a variation of the height 
of high-water was found to take place, which was inversely as the 
rise or fall of the barometer, and that a fall of the barometer of 0.622 
parts of an inch, was found to cause an increase of the height of the 
tide, equal to 8.78 inches in that port. To confirm this i 
and hitherto unsuspected cause of variation, had been one principal 
object of the researches of the learned gentleman; and, at his re- 
quest, Mr. Dessiou had calculated the heights and times of high- 
water at Liverpool for the year 1784, and compared them with the 
heights of the barometer, as recorded by Mr. Hutchinson for the 
same year: and by a most careful induction, it had turned out that 
the height of the tide had been on an average increased by one inch 
for each tenth of an inch that the barometer fell, ceteris paribus ; 
but the time was found not to be much, if at all affected. Mr. Lub- 
bock then proceeded to examine the semi-menstrual declination and 
parallax correction, and stated that the result was a remarkable con- 
formity between the results of Bernouilli’s theory and the results of 
observations continued for nineteen years at the London docks. 
But to render the accordance as exact as it was found to be capable 
of being, it was necessary to compare the time of the tide, not with 
that transit of the moon which immediately preceded it, but with 
that which took place about five lunar half days previously. To 
