E Q U 



Note. The word add in the Table denotes that the equation of time, 

 as there expressed, must be added to the apparent time, shewn by a 

 Dial or other instrument, in order to give the mean or equated time. 

 In those columns to which the word sub is prefixed, it implies that the 

 equation of time must be subtracted from the apparent time, in order to 

 give the true or correct time. 



If it be proposed to convert mean time into apparent, this is done by 

 a contrary process, by applying the equation of time to the mean time 

 given, with its title or sign changed, viz. subtracting instead of adding, 

 and adding instead of subtracting. 



EQUILIBRIUM of Floating Bodies. (Play fair, Eland.) 



1. "When the centre of gravity of a floating body is in the same verti- 

 cal line with the centre of gravity of the fluid displaced, the body re- 

 mains in equilibrium. 



2. If in a floating body, of which the transverse section is the same 

 from one end of the body to the other, a be the length of the water line, 

 c* the area of the section of the immersed part, d the distance between 

 the centre of gravity of the whole and the centre of gravity of the im- 

 mersed part, and i an indefinitely small inclination from the position of 

 equilibrium, the momentum of the force tending to restore the equili- 

 brium is 



If 3 z is greater than d, the force tends to restore the body to ita 

 state of equilibrium, or the equilibrium is that of stability. 



If -rpY d, there is no force tending either to restore or destroy 

 the equilibrium ; or the equilibrium is that of indifference. 



If ^ 3 g be less than d, the force becomes negative, and tends to over- 



set the body ; or the equilibrium is that of instability. 



When W remains the same, the stability is proportional to 



When the centre of gravity of the body is lower than the centre of 

 gravity of the immersed part, d is negative, and the quantity -^^ d 

 is affirmative, whatever be the magnitude of . t -* 



~ 108 



