304 Scientific Intelligence, Sfc. 



Esq., F. W. Jerrard, l^sf^.— Committee y C. Babbage, Esq., F.R.S., 

 F. Baily, Esq., Professor James Challis, Mr. Chatfield, Professor 

 Me Cullagh, Robert W. Fox, Esq., William Frend, Esq., G. 

 Jerrard, Esq., Professor Lloyd, J. W. Lubbock, Esq., Rev. Dr. 

 Lloyd, Provost of Trinity College, Professor Moll, Rev. G. Peacock, 

 Professor Rigaud, Professor Ritchie, John Robison, Esq., Professor 

 Stevelly, H. F. Talbot, Esq., Professor Wheatstone. 



Monday, '22nd August. — 1. Report on a Rock Salt Len^. — 

 Sir D. Brewster stated, that he had no regular report. Through 

 the kindness of Dr. Trail he had obtained from Cheshire some large 

 masses of rock salt, singularly transparent and homogeneous, and of 

 great purity, likely to afford a concave lens of considerable magnitude. 



2. 3Ir. LuhhocJts Report of Recent Discussions of Tide 

 Observations. — From the discussion of the Liverpool tides, by Mr. 

 Dessiou, he finds the diurnal inequality at Liverpool very consider- 

 able. The errors of prediction, at Liverpool and London, being 

 classified, the result obtained by Mr. Dessiou confirmed the influence 

 of atmospheric pressure on the tides. The law of the intervals, when 

 the discussion is instituted with reference to the transit immediately 

 preceding the time of high water, whether at London, Liverpool, or 

 Brest, depends partly on the phenomena as deducible from Bernouilli's 

 equilibrium theory, and partly upon the law of the intervals between 

 the moon's successive transits. The general conclusion of Mr. Lub- 

 bock, from an adequate discussion of tide observations by Mr. Jones 

 and Mr. Russell, is, that the equilibrium theory of Bernouilli satis- 

 fies the phenomena nearly, if not quite, within the limits of the 

 errors of the observations, and that it leaves little, if any thing, to 

 be accounted for otherwise. 



Mr. Whewell observed, that it appeared from Mr. Bunt's calcu- 

 lations, that though the observed laws of the tide at Bristol might 

 be made to agree with Bernouilli's theory of equilibrium tides, by 

 referring them to a certain anterior transit, so far as the changes due 

 to paralax are concerned ; yet, that this anterior period is not the 

 same for paralax as for declination ; so that there is no one anterior 

 period which gives theoretical tides agreeing with the observed tides ; 

 and, hence, the Bristol tides do not altogether, at present, appear to 

 confirm the result obtained by Lubbock from the London tides. 



3. Mr. Whewell reported respecting the Commitee appointed to 

 fix the relative level of the land and sea, with a view to determin^- 

 its permanence. He observed, that the Committee had not taken 

 any practical steps for the purpose for which they were appointed, 

 having found difficulties which required consideration ; but it was 

 stated, that it was intended to prepare to re-appoint a Committee 

 for this purpose, with instructions grounded upon the views at which 

 the members of the Committee have arrived, namely : 1. To strike 

 level lines for considerable distances along the land ; as, for example, 

 from Bristol to Ilfracombe, and from Bristol to Lyme Regis, with 

 great accuracy : the permanence of these two lines (independently 

 of reference to the sea) would determine the permanence of the 

 relative points. 2. To refer the extremeties of these lines to the 

 sea at each extremity ; the tides at the extremeties being of any 



