1822.] Cambridge Philosophical Transactions, Part II. 293 
“3. Clay slate associated with greywacke slate, and contain- 
ing subordinate parts, in which are conglomerate, common grey- 
wacke, and fine grained sandstone. 
«4, Serpentine surmounted by granular diallage rocks, and 
amorphous greenstone passing into greenstone slate. 
«5, An extensive porphyritic formation composed of felspar, 
diallage, and hornblende. 
“6, Nearly compact masses formed of the same constituents, 
associated with a very large-grained diallage rock, and alternat- 
ing with serpentine. 
“ 7, Serpentine irregularly associated with saussurite, diallage 
rock, greenstone, greenstone porphyry, greenstone slate, and 
granular felspar. 
«<8. Greenstone slate. 
«9. A formation apparently interlined both with the greenstone 
slate and the serpentine, and composed of chloritic slate (in one 
place associated with some thin beds of mica slate), talcose slate, 
and slaty felspar.” 
Prof. Sedgwick observes, that geologists have described two 
formations of serpentine, one belonging to primitive, the other to 
transition rocks; and he is of opinion that serpentine of the 
Lizard belongs to the latter class. 
XI. On Double Crystals of Fluor Spar. By W. Whewell, 
MA. FRS. &c. &c. 
This paper is accompanied by a plate, without which it would 
be unintelligible. 
XII. On an Improvement in the Apparatus for procuring 
Potassium. By William Mundell, BD. Fellow of Queen’s 
College. 
This paper, which is short, we shall probably include among 
scientific notices on a future occasion. 
XIII. On a large Human Calculus in the Library of Trinity 
Colleze. By the Rev. J. Cumming, MA. FRS. MGS. &c. Xe. 
Of this calculus, which weighs 32 oz. 7 drs. we have already 
given some account in a former volume of the Annals. 
XIV. On a Dilatation of Ureters, supposed to have been caused 
by a Malformation of their Vesical Extremities. By J. Okes, Esq. 
This paper is purely surgical, and devoid of general interest. 
XV. Geological Description of Anglesea. By J. S. Henslow, 
MA. FLS. MGS. Fellow of St. John’s College, and Secretary to 
the Cambridge Philosophical Society. 
This is a very elaborate communication, and is accompanied 
by a geological map, and illustrated by drawings of sections. 
Our limits will not allow us to give such an account of it as will 
do it justice. 
XVI. Some Observations on the Weather, accompanied by an 
extraordinary Depression of the Barometer during the Month of 
December, 1821. By the Rev. John Hailstone, MA. FRS. &c. 
It appears from Mr. Hailstone’s statement, that on the 25th of 
