STABLE EQUILIBRIUM OF THE OCEAN. 347 



should exist which would be capable of neutralizing the 

 action of the sun. In a memoir published in February, 

 1789, Laplace found that this cause must reside in the 

 ellipticity of Saturn produced by a rapid movement of 

 rotation of the planet, a movement the existence of 

 which Herschel announced in Xovember, 1789. 



The reader cannot fail to remark how, on certain 

 occasions, the eyes of the mind can supply the want of 

 the most powerful telescopes, and lead to astronomical 

 discoveries of the highest importance. 



Let us descend from the heavens upon the earth. 

 The discoveries of Laplace will appear not less impor- 

 tant, not less worthy of his genius. 



The phenomena of the tides, which an ancient philos- 

 opher designated in despair as the tomb of human curi- 

 osity, were connected by Laplace with an analytical 

 theory in which the physical conditions of the question 

 figure for the first time. Accordingly calculators, to the 

 immense advantage of the navigation of our maritime 

 coasts, venture in the present day to predict several 

 years in advance the details of the time and height of 

 the full tides without more anxiety respecting the result 

 than if the question related to the phases of an eclipse. 



There exists between the different phenomena of the 

 ebb and flow of the tides and the attractive forces which 

 the sun and moon exercise upon the fluid sheet which 

 covers three fourths of the globe, an intimate and neces- 

 sary connection from which Laplace, by the aid of a 

 series of twenty years of observations executed at Brest, 

 deduced the value of the mass of our satellite. Science 

 knows in the present day that seventy-five moons would 

 be necessary to form a weight equivalent to that of the 

 terrestrial globe, and it is indebted for this result to an 



