PRESIDENTIAL ADDRESS, B.A., 1871. 137 



of this principle and practical method, that the 

 British Association's Committee on Tides has for 

 the last four years been, and still is, working 

 towards the solution of the grand problem pro- 

 posed forty-eight years ago by Thomas Young in 

 the following words ; 



" There is, indeed, little doubt that if we were 

 " provided with a sufficiently correct series of 

 " minutely accurate observations on the Tides, 

 " made not merely with a view to the times of low 

 " and high water only, but rather to the heights 

 " at the intermediate times, we might form, by 

 " degrees, with the assistance of the theory con- 

 " tained in this article l only, almost as perfect a 

 " set of tables for the motions of the ocean as we 

 " have already obtained for those of the celestial 

 " bodies, which are the more immediate objects of 

 " the attention of the practical astronomer." 



Sir John Herschel's discovery of a right or left- 

 handed asymmetry in the outward form of crystals 

 such as quartz, which in their inner molecular 



1 Young's ; written in 1823 for the Supplement to the Encyclo- 

 peedia Britannica. 



