1S3P.] 



THE CIVIL ENCINEEU AND AUC'lHTECrS JOURNAL. 



353 



of the mixed gases from water in a confined space, and consetjucntly under 

 liigli ]ircssiire ; witli a view to ascertain, first, in wliat manner conduction 

 would he can'icd on, siiiiposing tliat the tid)e in wliicli the electrodes were 

 iutrodnced was qnite fiUcil with the electrolyte, and there were no space for 

 the accnnnilation of the gases ; secondly, whether, decomposition having heen 

 effected, rccomhination would take place at any given pressure ; ami lastly, 

 whether any ro-action on the ciu'rent-force of the hattery woulil arise from 

 the additional mechanical force which it would have to overcome. These 

 experiments the aiithor purposes pm'suing at some future time. 



' An CKjierimental hquinj 'into the Iiitliienci' of Nitroyen in promoting 

 Ver/etadte Decomposition^ and tlie connexion of tliis proccufi with t/ie groivtli 

 of Plants,' Iiy K. Kigg, lisq. 



The author considers it as a general fact, to which there arc very few if 

 any CNL'cptions, that vcgelahle hodics in the state in which they ai'e iiroduced 

 in nature, undergo spontaneous decomposition when ke))t under circumstances 

 favouring such an action ; and that, from the decomposition of each compound 

 products pecuUar to that suhstanee result. 



June 6. — F. Baily, Esq., V.P. in the chair. 



George Barker, Esq., was elected a Fellow. Tlie pajierread : 



' E.rperiin'iits on tlie Chemical Con.itil)ition of sepernl hodics n'Mch undergo 

 tJie Vinous Fennentation, and. on certain results of the Cttemical Jctiou,' hy 

 11. Kigg, Esq. 



The special ohject of this ]iaper is (o show, first, tliat sugar is not consti- 

 tuted of carhon and water only; secondly, that during the vinous fermenta- 

 tion water is decomposed ; thirdly, that neither pm^e carbonic acid nor alcohol, 

 in the common acceptation of tlie term, is the product of this chemical action; 

 and fomihly, that fermented liquors owe some of their valuable qualities to 

 peculiar products formed during fermentation. 



June 13. — J. W. Lubbock, Esq., Treasurer, in the chair. 



The following pajiers were read : — 



' Researches on the Tides. Tenth Series. On the Laws of Low Water at 

 the Port of Plymonth, and on the Permanency of Mean Il'aler,' by the Rev. 

 W. Whewell. 



In this memoir, the author investigates the question, how far the mean 

 irater, that is, the height of the tide midway between high and low water, is 

 permanent during the changes which high and low water undergo. That it 

 is so ap])roximately at Plymoidh, having been already ascertained by short 

 series of observations, it was desii'able to determine the real amount of this 

 permanency by induction from longer series of observations. A period of six 

 years was chosen for that purpose ; and the method of discussing these ob- 

 servations was the same, vntb shght modifications, as in former researches. 

 The height of low water, cleared from the elt'eets of lunar parallax, and very 

 nearly so from those of lunar declination, and compared with the height of 

 high water, similarly cleared, enabled the author to ascertain whether the 

 mean water also was alfected by the semi-menstrual inequality. The results 

 of the calculation show, that the height of mean water is, within two or three 

 inches, constant from year to year; and that, for each fortingbt, it has a 

 semi-menslrnal inc(|ualily amounting to six or seven inclies ; — tlic height 

 being greatest when the transit is at 6 h., and least when at 11 h., — the im- 

 mediate cause of this inequality being, that the semi-menstrual inequality of 

 low water is greater than that of high water : this inequality, however, is 

 probablymodiliedby local circumstances. These researches have also verified 

 the theoretical deduction, that the height both of low and of high water being 

 alfected liy the moon's declination, their mean height partakes of the varia- 

 tions in this latter element, in successive years, consequent on the change of 

 position of the moon's orbit. At Phnnouth, the increase in mean low water 

 amounts to about two inches for each degree of increase in the declination. 

 Ill the high water, this change is less marked. The parallax correction of 

 tlie height of low water is olitaincd from all years alike, by taking the residue 

 of each observation, which remains when the semi-menstrual iite((uality is 

 taken away, and arranging these residues for each hour of transit, according 

 to the parallax. Tlie declination correction is obtaineil in a manner analogous 

 to the parallax correction, from each year's observations, with some correc- 

 tion for the variation in the mean declination of the moon in each year. 



2. ' Researches on t/tc Tides. ElcventJi Series, On certain Tide Obserra- 

 tions 7nade in the Indian Seas,' liy the Uev. \V. \^'he\vell. 



This paper contains the results of the examination hy the author of certain 

 series of tide observations made at several places in the Indian Seas, which 

 were forwarded to the Admh'alty by the Hon. East India Company. These 

 localities were Cochin, Corringa River, Siirat roads in the Gulf of Cambay, 

 Gogah, on the opposite side of the same Gulf, and Bassadore, in the Island of 

 Kissmis, in the Persian Gulf. 



3. * On ttie Electrolysis of Secondary Compnunds' by J. F. I^aniell, Es(|. 

 The discovery of definite electro-chemical action naturally suggests the in- 



ipiiiy into the relative proportion of that jiart of a voltaic current which, in 

 the case of its decomposing a saline solution, is carried by tlie elements of 

 the water, and that part which is carried b\' the elements of the saline com- 

 ]iound, and into the definite relations, if any such there be, subsisting between 

 the two electrolytes so dccom))oscd. This question was the origin of the in- 

 vestigation which formed the subject of the present communication. 



' Erperi mental Researches on the mode of oj)eration of Poisons.' By J. 

 Slake, £s^, 



In this paper the author examines more particularly the action of those 

 poisons which appear to produce death hy art'eeting the nervous system. 



June 20. — John William Lubbock, Esq., V.P. and Treasurer in the chair. 

 Sir Thomas Dyke Acland, Bart., M.P., Edwin Guest, Esq., luid John Hogg, 

 Esq., M.A., were elected Fellows. 



* On the conditions of Equilibrium of an Incompressible Fluid, the particles 

 of v'hif'h are acted upon hy Accelerating Forces' by James Ivory, Esq., 

 k.II., M.A., F.R.S., 8:c. 



The intention of this paper is to examine the principles and methods that 

 have been jiroposcd for solving the problem of wliieh it treats, with the view 

 of obviating what is obscure and exceptionable in the investigation usually 

 given of it. The iiriiicijilc first advanced by lluyghens is clearly demonstrated 

 and is attended with no ditficulty. This principle requires that the resultant 

 of the forces in action at the surface of the finid in equilibrium and at liberty, 

 shall be perpendicular to that surface : and it is grounded on this, that the 

 forces must have no teuilency to move a particle in any direction upon the 

 surface, that is, in a plane touching the surface. In the Princijiia, Sir Isaac 

 Newton assumes that the earth, supposed a homogeneous mass of fluid in 

 equilibrium, has the figure of an oblate elliptical spheroid of revolution which 

 turns upon the less axis : and, in order to deduce the oblateness of the sphe- 

 roid from the relation between the attractive force of the jiarticles, and their 

 centrifugal force caused by the rotatoiy velocity, he lays down this principle 

 of equiUliriiim, that the weights or efl'orts of all the small columns extending 

 from the centre to the surface, balance one another round the centre. The 

 exactness of this principle is evident in the ease of the elliptical spheroid, 

 from the symmetry of its figure : and it is not difficult to infer that the same 

 principle is equally true in every mass of fluid at liberty and in eiiuilihrium 

 liy the action of accelerating forces on its jiarticles. In every such mass of 

 fluid, the pressure, which is zero at the surface, increases in descending below 

 the surface on all sides : from which it follows that there must be a jioint in 

 the interior at which the pressm-e is a maximum. Now this point of maxi- 

 iiiuni presbirre, or centre, is impelled equally in all directions by all the small 

 columns standing upon it and reaching to the surface ; and as the pressure in 

 everv one of these columns increases continually from the surface to the 

 centre, it follows that the central point sustains the total effect of all the 

 forces which urge the whole body of fluid. It follows also, fi'oin the jiro- 

 pcrty of a maximum, that the central point may be moved a little from its 

 place without any variation of the pressure upon it : which proves that the 

 forces at that point are zero. Thus the point of maximum pressm-e is in 

 stable equilibrium relatively to the action of* the whole mass of fluid : which 

 establishes Newton's principle of the e([uiponderance of the central columns 

 in every instance of a fluid in equihbrium and at liberty. The two principles 

 of lluyghens and Newton being estabUshcd on sure grounds, the next inqiury 

 is, whether they are alone suflicient for determining the figure of equilibrium. 

 Of this point there is no direct and satisfactory investigation: and in aiiply- 

 iiig the two principles to particular cases, it has been found that an equili- 

 brium determined by one, is not in all cases verified hy the other ; and even 

 in some instances, that there is no equilibrium when both principles concur 

 in assigning the same figure to the fluid. Further researches are therefore 

 necessary to dispel the obscurity still inherent in this subject. In a mass of 

 fluid in equilibrium, if we suppose that small canals arc extended from a 

 liarticle to the surface of the mass, the |iarticle will be impelled with ecpial 

 intensity by all the canals : for, otlierwise, it would not remain immovable, 

 as an equilibrium requires. It has been inferred that the equal pressm'es of 

 the sm-rounding fliud upon a jiarticle, are sufficient to reduce it to a state of 

 rest. Hence has arisen the principle of equaUty of pressure, which is gene- 

 rally admitted in this theory. Now, if the matter be considered accurately, 

 it will be found that the only point within a mass of fluid in eipiilibritnu 

 which is at rest hy the sole action of the sun'ounding fluid, is the central 

 point of Newton, or the point of maximum pressure. The reason is that, on 

 account of the maximum, the pressure of all the canals terminating in the 

 centi-al point, increases continnally as the depth increases; so that, liesides 

 the pressures of the canals, there is no other cause tending to move the par- 

 ticle. With respect to any other particle, the pressure caused by the action 

 of the forces in some of the canals standing upon the particle, will necessarily 

 increase at first in descending below the surface, and afterwards decrease ; so 

 that the clfcctive pressure transmitted to the particle, is produced hy the 

 action of the forces upon a part only of the fluid contained in such canals. 

 If a level surface be drawn through any jiarticlc, it is proved in the paper, 

 that the equal pressures of the surroimdiiig fluid on the iiarticle, arc caused 

 solely by the forces which urge the portion of the fluid on the outside of the 

 level" suif ace, the fluid within the surface contributing nothing to the same 

 eft'eet. Thus a particle in a level surface is immoveable by the direct and 

 tiansniillcd action of the fluid on the outside of the level suiface ; hut it wdl 

 still be liable to be moved from its place unless the body of fluid within the 

 level surface have no tendency to change its form or position nyall the forces 

 that act on its own particles. Wli.at has been said not only demonstrates the 

 insufficiency of the ])riiiciple of eqn.ality of pressure for determining the figure 

 of equilibrium of a fluid at liberty, but it points out the conditions which are 

 necessary and sufficient for solving the' problem in all eases. The pressure 

 must lie a niaximum .'it a central point within the mass : it must be zero at the 

 surface of the fluid : and, these two conditions being fulfilled, there will neces- 

 sarily exist a series of interior level surfaces, the pressure being the same ,at 

 all the i)oints of every siu-facc, and varying graduallj- from the maximiuu 



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