362 OF THE STABILITY OF FLOATING BODIES AND OF SHIPS. 



more perspicuous and comprehensive definition, which may be scien- 

 tifically read in the following manner. 



1 . The Equilibrium of Stability, is that property in floating bodies, 

 by which on being slightly inclined to either side, they endeavour to 

 redress themselves and to recover their original position. 



2. The Equilibrium of Instability, is that property in floating 

 bodies, by which on being slightly inclined from the upright position, 

 they tumble over in the fluid and assume a new situation, in which 

 the conditions of floating again occur. 



3. The Equilibrium of Indifference, is that property in floating 

 bodies, by which they are enabled to retain whatever position they 

 are placed in, without exhibiting the smallest tendency, either to 

 regain the original position, or to deviate farther from it. 



In addition to the different species of equilibrium described above, 

 there are several other terms of very frequent occurrence in the 

 doctrine of floatation, which it will be proper to explain before we 

 proceed to develop the laws that regulate the conditions of stability. 

 The most common and the most important of the terms here alluded 

 to, are the following. 



450. DEFINITION 1. The Centre of Effort, is the same with the centre 

 of gravity of the entire floating body ; it is that point through which 

 the horizontal axis passes, and about which the body is supposed to 

 revolve. 



DEFINITION 2. The Centre of Floatation, or the Centre of Buoy- 

 ancy, is the same with the centre of gravity of the immersed part of 

 the floating body, or it is the same as the centre of gravity of the fluid 

 displaced in consequence of the floatation. 



DEFINITION 3. The Line of Pressure, is the vertical line passing 

 through the centre of effort, in the direction of which, the body is 

 impelled downwards by means of its own weight. 



DEFINITION 4. The Line of Support, is the vertical line passing 

 through the centre of buoyancy ; it is either parallel to, or coincident 

 with the line of pressure, and is that in whose direction the body is 

 propelled upwards by the pressure of the fluid. 



DEFINITION 5. The Axis of Motion, as we have already observed 

 in treating of the positions of equilibrium, is the horizontal line passing 

 through the centre of effort, and about which the body revolves on 

 being deflected from its original position. 



DEFINITION 6. The Transverse Section of the Solid, is that indi- 

 cated by a vertical plane at right angles to the axis of motion, and 

 separating the body into any two parts : all the transverse sections 



