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JOUENAL OF THE PLYMOUTH INSTITUTION. 
THE PEINCIPLES ON WHICH SHIPS' SAIL-CAEKYING 
POWEK AND STEADINESS IN A SEA-WAY DEPEND. 
ABSTRACT OF MR. W. FKOUDE's PAPER. 
(Read March 2nd, 1871.) 
Apologetic admission of incompleteness and probable want of 
clearness, on the score of inexperience, personal defects, and 
greatly occupied time. 
Stability and sea-worthiness principally considered under two 
aspects; namely, in respect of (1) stiffness and (2) steadiness. 
Stiffness" is the power to stand up under canvas, or resist 
upsetting forces. 
Steadiness is the freedom from oscillation in a sea-way." 
"Stiffness" is more usually termed stability, which term is, 
however, misleading as seeming to imply steadiness also, although 
for the most part it produces "unsteadiness." Stiffness should 
first receive separate consideration. The conditions which govern 
steadiness will be found to depend on the conditions of stiffness 
taken in conjunction with the theory of waves. 
The stiffness of a solid body resting on a solid is less charac- 
teristically different from that of a floating body than is popularly 
thought; since from inherent compressibility and extensibility of 
all substances, a solid body of whatever substance undergoes de- 
flection or inclination when exposed to strain : a table on India- 
rubber legs represents, only in magnified form, what happens to 
one with timber legs. 
Popular statement that a structure will stand so long as "the 
perpendicular of the centre of gravity falls within the base" shown 
to be not exact in principle, and often misleading. 
Extract from letter of Mr. Brunei. 
Terms "stable" and "unstable" equilibrium explained. 
Archimedean principle that a body which displaces any part of 
a fluid receives a support equal to the weight of the fluid dis- 
placed. Popular proof of this. 
Flotation happens when the weight of fluid displaced exceeds 
that of the displacing body. 
