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 v/ith 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, he. 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 interesting 

 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, cateris 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 



