342 Mr. A. M. Worthington on Laplace's 
fluide sur ce canal, et cette action est egale a K; 2° a Paction 
du plan sur le meme canal. Mais cette action est detruite par 
l'attraction du fluide sur le plan, et il ne peut en resulter dans 
le plan aucune tendance a se mouvoir; car, en ne considerant 
que ces attractions reciproques, le fluide et le plan seraient 
en repos, Taction etant egale et contraire a la reaction; ces 
attractions ne peuvent produire qu'une adherence du plan au 
fluide, et Ton peut ici en faire abstraction. II suit de la 
que le fluide presse le point R avec une force ^gale a 
P + K +g .VS-K, ou simplement P +g . VS." Thus show- 
ing quite clearly that he did not regard the pressure K as 
capable of being transmitted to a solid surface. 
It is important, however, to observe that in the next page, 
when comparing the pressures at the two sides of the plate at 
another level, he does not take the trouble to cancel K in this 
way, but speaks of it as transmitted to the plate, but balanced 
by an equal pressure transmitted from the other side. He 
writes carelessly in fact. And though in the very next para- 
graph, in treating in precisely the same manner the pressure 
at a third point, he again accurately cancels the K before it 
reaches the plate, it is probable that he does so because of the 
necessity of getting rid of it (there being at this point nothing 
but atmospheric pressure at the other side of the plate), rather 
than from a sense of the importance of using language that 
should be strictly correct. 
It will be observed, however, that he consistently speaks of 
the elevation of the liquid in a capillary tube as due to the 
attraction of the meniscus, and not to the excess of pressure 
at the plane surface. 
I have quoted these passages because they show clearly that 
Laplace did not himself fall into the error of regarding the 
pressure K as transmitted to immersed solids, or of consider- 
ing the elevation of the liquid as due to a vis a tergo having its 
origin in the free surface. It is not surprising, however, that 
others should have fallen into this mistake when we find 
that he occasionally used language which could only encou- 
rage such a view. 
It may be noticed that, through taking for granted the 
equilibrium of all the liquid except the single canal which 
he considers, Laplace does not at first discover the real seat 
of the external force by which the liquid is elevated. In 
the Second Supplement, however, proceeding by a different 
method, he traces it to the action of the solid matter of the 
tube just beyond the edge of the liquid where it meets the inner 
wall of the tube. 
It is well known that Young objected to Laplace's theory 
