330 



November 25, 1841. 



SIR JOHN WILLIAM LUBBOCK, Bart., V.P. and Treas., 

 in the Chair. 



The Right Honourable the Earl of Lovelace was balloted for, 

 and duly elected a Fellow of the Society. 



The following papers were read, viz. — 



1. "Explanation of the construction, positions, comparisons, and 

 times of observation, of the Meteorological Instruments at the Royal 

 Observatory, Greenwich, with which the Observations have been 

 made that are contained in the sheets of Meteorological Observa- 

 tions, forms 1 and 2, for each month from 1840 November to 1841 

 July, both inclusive, sent to the Royal Society in 1841, October 26." 

 By George Biddell Airy, Esq., M.A., F.R.S., Astronomer Royal. 



2. " On the Laws of the rise and fall of the Tides in the River 

 Thames." By George Biddell Airy, Esq., M.A., F.R.S., Astronomer 

 Royal. 



The conclusions arrived at by the author, and stated in this paper, 

 were derived from an extensive series of observations of the tides, 

 made, on his suggestion, at the Royal Victualling Yard at Deptford, 

 under the superintendence of Captain Shireif, R.N. The object of 

 the first series of observations was simply to ascertain the times of 

 high and low water, for the purpose of ascertaining the duration of 

 the rise and fall of the tide : the height of the water was observed at 

 every quarter of an hour, night and day, during half a lunation. The 

 curves representing the law of rise and fall of the water were found 

 to be different for high tides and for low tides ; and both are sensibly 

 different from the line of sines. The author then investigates ma- 

 thematically the motion of a very long wave, such as a tide-wave, in 

 a rectangular canal, whose section is everywhere the same, on the 

 supposition that the extent of vertical oscillation bears a sensible 

 proportion to the mean depth of the water; and deduces an expres- 

 sion for the vertical elevation of a particle at the surface. This ex- 

 pression supposes the canal unlimited at the end farthest from the 

 sea. If the canal be stopped by a barrier, the expression changes its 

 form. The formulae obtained by the author enable him to explain 

 a circumstance, hitherto perplexing, namely,'that the age of the tide 

 is different as inferred from the height of the high water, or from 

 the time of high water ; being always greater in the former mode of 

 estimation. 



3. " Register of Tides, observed at Coringa, from January 1st to 

 June 30th, 1841." 



4. "Meteorological Journal, from the 20th April 1840 to the 

 29th April 1841. Kept at the Falkland Islands on board H.M. 

 Ketch, Arrow." 



