Proceedings of the Cambridge Philosophical Society, S77 
serpentine, intermixing with the greatest confusion. It also 
passes to a rock between hornstone and jasper. 
Dec, 3. — communication was read, by the Reverend J. 
Gumming, Professor of Chemistry, “ On a remarkable Human 
CalculuSy in the possession of Trinity College.'” This calculus 
weighs 3S ounces ; its specific gravity is 1.756, and it measures 
15| inches in circumference. Its nucleus is lithic ; to this suc- 
ceeds a considerable portion of the oxalate of lime variety, fol- 
lowed by layers of the triple crystals, covered by a thick coat- 
ing of lithic, which is occasionally broken by a layer of the 
triple crystals, and the external surface is principally composed 
of the fusible calculus. Professor Gumming notices also a cal- 
culus composed of vegetable matter and the phosphates, found 
in the intestines of a horse, which weighs 64 ounces, and mea- 
sures 37 inches in circumference. 
Mr Henslow proceeded with his paper on the Geology of 
Anglesea. The chlorite-schist is succeeded by clay-slate and 
greywacke, which generally possesses a laminated structure, 
the plates inclined at a very considerable angle to the horizon, 
and probably wholly independent of any original order of de- 
position. In one place, the lower beds of greywacke assume 
the form of a conglomerate of rolled pebbles, which Mr Hen- 
slow shews to be a deceptive appearance, the nodules being in 
fact of a concretionary nature. Old red sandstone occurs on a 
fine grained red and green sandstone, but more generally as a 
breccia, composed of angular fragments of quartz and slate. 
The greater part appears to have undergone considerable alte- 
ration since its deposition, having become more crystalline and 
compact from the ingredients running together, and in some 
places forming a homogeneous quartz-rock. This is the oldest 
formation in Anglesea, in which traces of organised bodies were 
found. These consist of the casts of small Anomiae and other 
bivalve shells. The mountain-lime and coal-measures are found 
conformable to the old red sandstone in one part alone of Angle- 
sea. In every other instance they terminate abruptly against 
the schist. The grit is observed to penetrate the limestone in 
large cylindrical masses, in the same manner as gravel and sand 
penetrates the chalk. Strata of fine grit shew a tendency to 
assume a laminated structure oblique to the direction of the 
