S*. 16. W. 

 13 43 



3 38 ......... 0.521 



......... + 0.017 



Minor axis ......... 0,504 



The sign + shews that that half of the ring, or of the orbits, which it 

 most distant, is more north than the centre of Saturn, and the sign 

 hews it to be more south. 



SCREW. 



When there is an equilibrium upon the screw, P : W : *. the distance 

 between two contiguous threads, measured in the direction of the axis Z 

 the circumference of the circle which the power describes. 



Hence if d = distance between the threads, a = radius of the circle 



described by the power, P : W :: d : 2 * a ; .*. P , from which 



equation any three of the four quantities P, W, a, d being given, the 

 fourth may be found. 



In the endless screw, which works in, and turns a dented wheel, let 

 a = length of the lever, R = radius of the wheel, r = do. of the axle, 

 the rest as before j then 



p : w :: dr : 2* R ; 



P- 



SEA WATER, gpecific gravity of. 



Table of the specific gravity of sea water in various parts of the globe, 

 is ascertained by Dr Marcet. 



1.01915 

 1.01418 

 1.01901 

 1.01523 

 1.00057 

 1.16507 

 



From the preceding facts, Dr Marcet concludes, 

 1. That the Southern Ocean contains more salt than the Northern in 

 the ratio of 1.02919 to J, 02757,, 

 259 



