51 
district. Not a river or torrent nor even a purling brook but carries with 
it particles of solid matter derived from the land over which it flows. The 
mighty Niagara and the miniature waterfall are each engaged in eating 
into the strata over which they fall, and the deep pool at the foot of a 
cascade shows the power of dropping water. Kain softens and carries 
away the surface of the ground. Frost expands the moisture lying in the 
interstices of rocks and splits asunder huge blocks of stone, hurling them 
into the valleys. The heats of summer occasion cracks in soft strata, which 
widen and cause separation of large masses, as in the Isle of Wight and 
other districts; and moving ice transports huge boulders and smaller 
masses of stone from their parent rock to distant localities. 
In conclusion, allusion was made to the effects of denudation in producing 
the varied and picturesque scenery of our own and other countries. 
X. 
On the Structure of Rubies, Sapphires, Diamonds, and 
some other Minerals, 
By H. C. Sorby, F.R.S., and P. J. Butler, 
From the Proceedings of the Moyal Society, 1869. Communicated by 
P. J. Butler, Esq,,* and read by the Son. Secretary at the General Meeting, 
December 1st, 1870. 
Eor many years Mr. Butler has had the opportunity of examining very 
many rubies, sapphires, and diamonds, and has taken advantage of it in 
forming a most interesting collection, cut and mounted as microscopical 
objects. He had very carefully studied the included fluid- cavities, and 
ascertained many curious facts. Mr. Sorby had for some time paid much 
attention to the microscopical structure of crystals, and published a paper+ 
* Mr. Butler desires here to express his thanks for the courtesy of the 
Royal Society in granting him through their Secretaries, Dr. Sharpey 
and Professor Stokes, the use of the stone from which the plate illustrating 
the paper has been printed. 
t Quarterly Journal of Geol. Soc, 1858, vol. xiv. p. 453, 
