ON CAPILLARY ACTION. Jj^ 



Remarks on Mr. La Place's Theory of Ca'pillary Action. 

 In a Letter from Thomas Knight, Esq. 



ToMr.NICPIOLSON. 

 SIR, 



.MONG the ohiections that may be made to Mr. La '^^j «''•*■*»■ t* 



- T n Plate 



Place's theory of capillary actiou, tiiere is puej that 1 should 



be glad to take notice of, through the medium of your va- 

 luable publicatiou. 



The errour alluded to (as well as many others) I have 

 indeed pointed out, in an "Examination of Mr. La Place's 

 Theory," published about a year ago: but it appears, from 

 the present number of the Monthly Keview, that what I 

 very clearly expressed has been totally misrepresented. / 

 hope It h'dL^heewmisunderslOud*. - m; r 



It is convenient, in Mr. La Place's view of the so bject, Action of ^ 

 to consider, separately^ the action of a concave "i^'^^^^'u^, ^^^'^^V^^.^w 

 and that of a fluid mass with a plane surface, on a slender a plane sur- 

 columnof fluid. face consider. 



--^■jc-"* *^*1 separately: 



This author shows, in a satisfactory and iillfyeniDtis man- butthesame 



uer, that, by the action of the meniscus, the column is "^°^^ ^^ ^^^^7 

 *' . soning appli'' 



ur^ed upwards. Now, the same mode of reasoning that is cable to a 



applicable to a ineniscius, must also be applicable to a mass J"^^^ of auj 

 ofany other form. ,That very yc^w^ reasoning ought, there- 

 fore, to have been employed in determining the action of 

 the n^ass vith a plane surface: and thus it would have been 

 found, that by ijiis also the colutnn is xwg^d upioards, ' 



Instead of this, Mr. La Place, by a process of quite athoughMr. L. 



different kind (which the Monthly Reviewer esteems vastly endeavour* 

 • ^ . •' ,. . ^ to show the 



.simple a,nd ingenious), attempts to sho\v, that this mass with contrary. 



a plane 'surface urges the column downwards. 



The falsehood of which mUy be proved in a moment; for, His^ouv 



if we consider any point in the mass, it is easy to see that it ' ^'^^' 



will urge the column neither way, or will urge it upwards: 



and this, by Mr. La Place's own reasoning which he had 



used \vhen treating of the meniscus. 



• The author patses over every material argument in the examination} 

 iuid has the prud-Jiice not lo defenU Mr. L» flake's g^nstx^ theory. 



I affifm^d, 



