85^ Professor JamesonV Geognostkal Description 
the boilers. Each of the two cylinders has a diameter of 17 
inches, and ^ stroke of 18 inches, and revolves 50 times in a 
minute. The area of the piston being about S27 inches, it- will, 
when worked with steam of 50 lb. have the power of 100 horses. 
Mr Sullivan gives the following enumeration of the pro- 
perties of this new engine : It works with or without a con- 
denser; — it has a rotatory movement ; — it requires no ponde- 
rous balance-wheel ; — -it is adapted to high steam ; — it is at- 
tended by no inconvenience from the rapidity of its stroke or 
movement ; — it has no inert mass of machinery to move recipro- 
cally ; — it is more powerful, proportionally, from its using steam 
as strong as that in the boiler ; — it is of a simple and durable 
construction, and, by a combination of two similar machines at- 
tached to the same common intermediate axis, operating so as 
to give nearly an equal power at every moment of its operation, 
seems to combine every thing desirable in an engine for the 
purposes of navigation.” 
Art. XXII. — Geognostical Description qf the Neighbourhood 
of Edinburgh. By Professor Jameson. 
Part I, 
Edinburgh is built on a central and high ridge, about 
a mile in length, which extends from north-east to south-west ; 
and on two low and rising grounds, having nearly the same ge- 
neral direction and length. On the central and high ridge are 
situated the Castle, with the lofty and picturesque buildings of 
the Old City ; while the northern rising ground is nearly covered 
with the splendid streets and squares of the New Town, and 
the southern principally with the ancient suburbs of the city, and 
numerous streets of modern date. The northern rising ground 
rises rapidly to its highest elevation in the centre of the New 
Town, and again declines first gently, and then rapidly, towards 
the south, into the valley of the North Loch. Towards the west it 
is continuous with tlie neighbouring flat country, and on the east 
it is bounded by the Calton Hill. The central ridge, for a con- 
siderable part of its length, is very steep, both to the north and 
to the south, and is terminated on the west by the Castle-rock, 
