77 



and that the ratio of the velocities of these two rotations, together 

 with the length of the peg, determines the angular inclination of the 

 top, contrary to the received explanation as given by Euler and other 

 mathematicians. 



The law is further applied to the effect produced upon a falling 

 body by the axial rotation of the earth, in the discussion of which, 

 La Place, in the opinion of the author, has committed two important 

 errors one in denying any deviation towards the equator, the other ; 

 in his calculation of the amount of the deviation towards the east. 



This is followed by an investigation of the motion or direction of 

 flight of a cannon-ball or shell fired in a northerly or southerly 

 direction, from which it appears that a large shell will be subject to 

 a deviation from the true line of projection, in consequence of the 

 earth's rotation, amounting to no less than 22 feet. 



The author then refers to the well-known experiment of M. Fou- 

 cault for proving sensibly the rotation of the earth, and shows from 

 calculation that the errors which would be sufficient to vitiate the 

 results in this experiment are so extremely minute and so difficult of 

 avoidance by any perfection of manipulation which can be employed, 

 that its performance cannot perhaps be safely adduced as proving 

 such rotation. 



The author illustrated his views by the exhibition to the meeting 

 of a model apparatus, in which the vertical and horizontal motions 

 may be variously combined, but which could not be intelligibly de- 

 scribed without a series of complicated drawings unfitted for the 

 compass of a mere abstract. 



