Proceedings of the Cambridge Pliilosoplucal Society. 185 
equal lines drawn in piano. On the same principle, he demon- 
strated a series of other propositions, which became the founda- 
tion of precepts for the application of the perspective to more com- 
plex cases. He afterwards gave some details on the advantages 
to be derived from an extended application of similar methods. 
3. Dr E. D. Clarke communicated his discovery of Cadmium 
in some of the English ores of zinc, and gave a short account 
of his mode of operating. 
4. The results of a series of experiments made by Captain 
Fairfax, in order to determine the soundings at sea, by observing 
the times of descent of different waves, were read to the Society. 
March 6 . — 1. A letter from the Rev. J. Hailstone was read by 
one of the Secretaries. It described an appearance presented 
by the weathered surfaces of several specimens of calcareous 
sandstone found in the cliffs near Scarborough. The exterior 
surface of the specimens presents a. number of club-shaped or 
conical masses, sometimes branching one from the other, which 
stand out in high relief. The appearance was supposed to take 
its rise from some marine production of the actinia or mollusca 
tribe, the organization of which is known to be very confined, 
and whose substance bears a small proportion to the superficial 
extent which the animal is enabled to occupy when expanded 
by water. 
2. The President concluded his communication on the sub- 
ject of isometrical-perspective. 
3. Extracts were read from a paper On the Reduction of 
certain Classes of Functional Equations to Equations of finite 
differences.” By J. F. W. Herschel, Esq. 
4. A paper by Mr J. Okes, On some Fossil remains of the ' 
Beaver found near Chatteris in Cambridgeshire. The first 
part of his paper contained some historical details, proving the 
beaver to have been at one time an inhabitant of Great Britain. 
It was then shewn, by quotations from Dugdale’s History of 
the Fens, that the place where the bones were found, had for- 
merly been a considerable branch of communication between the 
Ouse and the Nen, though it has now been choaked up for more 
than two centuries. After giving some anatomical details, in- 
tended to prove that the fossil bones in question belong to an 
animal of the. same species as the beaver of Canada, the au- 
