NOTES. 



487 



other's effects, so that the water is smooth there, while it is agitated in the in- 

 termediate spaces. 



NOTE 157, P. HI. The centrifugal force may, fyc. The centrifugal force 

 acts in a direction at right angles to N S, the axis of rotation, fig. 30. Its effects 

 are equivalent to two forces, one of which is in the direction bm perpendicular 

 to the surface Q m n of the earth, and diminishes the force of gravity at m. 

 The other acts in the direction of the tangent m T, which makes the fluid par- 

 ticles tend towards the equator. 



NOTE 158, p. 119. Analytical formula or expression. A combination of 

 symbols or signs expressing or representing a series of calculation, and in- 

 cluding every particular case that can arise from a general law. 



NOTE 159, p. 122. Platina. The heaviest of metals; its colour is between 

 that of silver and lead. 



NOTE 160, p. 123. Fig. 38 1,9 a perfect octa- 

 hedron. Sometimes its angles, A, X, a, a, 

 &c., are truncated, or cut off. Sometimes 

 a slice is cut off its edges A a, Xa, a a, &c. 

 Occasionally both these modifications take 

 place. 



NOTE 161, p. 124. Prismatic crystals of 

 sulphate of nickel are somewhat like fig. 62, 

 only that they are thin, like a hair. 



NOTE 162, p. 125. Zinc, a metal either found as an ore or mixed with other 

 metals. It is used in making brass. 



NOTE 163, p. 125. A cube is a solid contained by six plane square surfaces, 

 as fig. 39. 



Fig. 39. Fig. 40. 



C 





