236 



Mr. HOPKINS, ON THE TRANSPORT OP ERRATIC BLOCKS. 



If p be sufficiently small, 



1 («)i - v^y 



and 



An = - . — 



I 

 I 



I,. 



nearly,. 



• 0), 



.(10) 



approximately. 



I have supposed the section (Z, P^) of the surface of the wave to be a straight line. It will 

 generally be some curved line having its convexity turned upwards or downwards according to the 

 nature of the disturbance in which the wave originates. In the former case, the value of s would 

 be greater, and in the latter less than that here determined, which may therefore be considered as 

 an approximation to the mean of the values of s for different waves, in which t>, v^ V and I should 

 be the same, but the original mode of disturbance, and therefore the form of the wave, different. 



21. The following table exhibits numerical values of the velocity (F) with which the wave is 

 propagated, of the maximum velocity («,) of the attendant current, and of the space (s) through which 

 a block may be transported, for certain values of the original depth (i/) of the water, of the height 

 (Aj) of the wave, and of tlie velocity (Dj) of the current just sufficient to move the block. The 

 values of H and h^ are given in feet, those of V, t), and iij in miles, the velocities being estimated by 

 the number of miles described in an hour; s is given in terms of I the breadth of the wave. The 

 values of* are calculated from equation (9). The last column contains Sq calculated from (10). 



