Geology and Mineralogy. 323 
the extreme violet. A compound prism or parallelopiped thus 
formed affords the best means of studying solar we 
and spots and ee reversed lines of ros chromosphere. The prism 
: Lisgtige eae o the Transit of us Comm mission, since clear- 
s of ielntsion: can be obtained er great dispersive and 
see magnifying power. ft ane obviates confusion arising from 
aor: oo can be obtained by the use of this sigonaee taht. 
endus, Jan, aie 1882, pp. 155-157. 
8. On ¢ ery of Potassium Chloride found in the ceirdbee 
of i Se he or Absinth (Arte deatcge someones L.; by E 
CLAAssEN. (Communicated),—Some time I had occasion 
to aes use of the above named atinict a deci was surprised to 
find in it many perfe ectly transparent, yellowish, almost colorless 
crystals of great regularity of form. The largest were about 
: fabian 
were combinations of the octahedron ain cube, with either a pre- 
crystals were potassium shlos 
his salt is commonly pose in cubes, and the uncommon forms 
described are sis es to the presence of organic substances 
in the wormwood extrac 
Cleveland, Jan., 1882. 
Il GEoLoGy AND MINERALOGY. 
. Tides in atid Beteeag er’ time.—Mr. G. H. Darwin, whose 
edt on the “ Pre on a Viscous Solid” (Phil. Trans., 1879), 
called out the eee: of all, Astronomer Royal of rela nd, 
on great tides as a ecleiptoal agency in early time, states, in Na- 
ture for January 5th, his non-coneurrence with Mr. Ball in his 
y Mr. Ball, he 
ould locate in regeclopiod periods. He had contemplated 
on possibility of tides two or three times as high as at present in 
the earliest geological time, and observes that this estimate is 
Sipsrantd rather excessive than deficient. As in his former paper, 
Mr. Darwin states that an increase of rain-fall would be an un- 
nc is, and th i 
out ten netic iacatebs spn sh and: Mr. ane ie 
se ote th h must have been rotating in about s hour 
the trades would pr obably have hed a velocity of 32 their presetia 
velocity, and, consequently, vortical storms would have had pro- 
