TIDAL OBSERVATIONS. 201 



St. Petersburg, and the Academy of Sciences in Paris ; and we trust that 

 by that means each country will possess a prototype copy of the Metre, 

 made in relation to the Metre of the Archives in Paris, all the copies being 

 made of the same material, compared by the same method and instru- 

 ments, at the same temperature, and preserved in the same manner. Her 

 Majesty's Government had deputed Prof. Airy, the lamented Prof. Miller, 

 and Mr. Chisholm, the Wardens of the Standards, to attend the Inter- 

 national Commission. Your Committee have reason to believe that it is of 

 the utmost importance to continue to give to this question unremitting at- 

 tention, and they are connnced that their action has been eminently useful 

 in guiding the Legislature, both of this country, of the Colonies, and even 

 of other countries, to the great question of uniformity of Weights and Mea- 

 sures aud Coins in the interest of Science. In pursuance of this object, j^our 

 Committee are anxious of diffusing as much information as possible. Especially 

 they are desirous of supplying those who conduct scientiiic researches with 

 the means of cariying them on in Metric Weights and Measures, as the most 

 universally known, the most exact, and the most economical as regards time ; 

 for which purpose they would be glad to purchase one or two sets of Metric 

 Standards. And for these, and other jxirposes, they suggest the reappoint- 

 ment of the Committee, with a grant of at least £75. The advantage of 

 introducing a universal system of Weights and Measures is well admitted. 

 Men of Science of all countries, to a large extent, use already a universal 

 vocabulary in this respect ; and your Committee trust that the British Empire 

 will ere long throw on the side of such a reform the immense weight of her 

 example and influence. 



Report of the Committee appointed for the purpose of promoting the 

 extension, improvement, and harmonic analysis of Tidal Observa- 

 tions. Consisting of Sjr William Thomson, LL.D., F.R.S., Prof. 

 J. C. Adams, F.R.S., J. Oldham, William Pakkes, M. List. C.E., 

 Prof. EankinEj LL.D., F.R.S., and Admii-al Richards, R.N., 

 F.R.S. 



Jteport drawn up hy Mr, E, Roberts. 



82. The work performed for the Tide Committee since the last Meeting 

 of the liritish Association has consisted chiefly in the evaluation of tide- 

 components in a similar manner to that described in the previous Eeports. 



S;3. Mr. Parkes having again placed the tracings of the curves of the 

 Kurrachee (Manora) self-registering tide-gauge at the disposal of the Com- 

 mittee, a second year's observations have been read off and completclj^ re- 

 duced. In addition to the tide-components evaluated for Liverpool and 

 llamsgatc, others (named for brevity J and Q) have been introduced to 

 correct the lunar diurnal (declinational) tides for parallax. These com- 

 ponents have been found to have sensible values for Kurrachee, where the 

 diurnal tides are comparatively l^rgc. The solar elliptic semidiurnal (E. and 

 T) components have also been included, now that two complete years' ob- 

 servations were available. The whole of the values of these tide-components 

 is contained in the previous Report (§ 07), the work having been completed 

 before the Report was printed. The correcting of the calculated heights 

 (§ 7U) for these additional components will doubtless bring them stUl nearer 



