EXTRACTS—NATURAL HISTORY. 
135 
Calanthe den si flora, Clustered Calauthe. r J'his is a native of the inoun - 
tains of Sylhet, whence it was obtained by Dr. Wallich. The dowers are yellow. 
It is a terrestrial species, growing very freely in loam and decayed vegetable 
matter in a damp stove j and is propagated by a division of the crown of the 
root.— Bot. Reg. - 
MUSACE.E. 
Heliconia pulverulenta, Powdered Heliconia. All the Plantain Tribe 
are remarkable either for the beauty, or size, or singularity of their foliage j but 
this, although inferior to many in the magnitude of its parts, yields to none in 
beauty. It is impossible to imagine any thing more delicate than the blue bloom 
which thickly covers the underside of the leaves, or more brilliant than the vivid 
scarlet of the flower-leaves or spathes, among which nestle, as it were, a few 
bright green flowers.— Bot. Reg. 
NATURAL HISTORY. 
Geological Positions.* —First Line of Argument.—1. The chalk is a ma¬ 
rine formation, and consequently was deposited as a sediment, in the bed of the 
sea. 2.—As the chalk now forms an extensive member of the secondary 
strata of our dry lands, there must have been a time when it at first became dry 
land. 3, The action of the waves upon a sea coast is unceasing, and the effects 
of this action are more or less visible on every shore, according to the consistency 
of the rocks, which compose it. 4.—From the very first moment that the chalk 
became dry land, this unceasing agent must have operated as it still does, upon 
such portions of it as extended to the level of the sea. 5. From that time to 
the present, is the exact age of the chalk as a dry land. 6. The chalk is never 
superficially level, but is on the contrary, invariably of a rounded and sloping 
surface. 7. The surface of the chalk is always grooved out into valleys, divided 
by ridges c f various degrees of steepness, but invariably smooth. 8. These val¬ 
leys seldom contain water, or running streams; they consequently have never 
been altered in their surface by the erosion of rivers, since they became valleys. 
9. Notwithstanding this absence of rivers, the chalk valleys universally open 
either into larger valleys, which lead to the level of the sea, or they individually 
point to this exact level, thus plainly bespeaking the action of the waters. 10. 
As all chalk valleys, unaffected by the corroding action of the waters, have this 
character and tendency, we are certain that all other valleys, though now cut 
short by precipitous sea cliffs, had originally the exact same form and tendency. 
11. Our present chalk cliffs are constantly encroaching upon the lands, by a 
progress more or less rapid, according to circumstances. 
12. As rotundity is a universal characteristic of the chalk, and as the cliffs 
will thus all be higher and further back, a thousand years hence, than they now 
are, it follows that they were more in advance, and consequently lower a thou¬ 
sand years ago. 13. Having the perpendicular of the cliff, and the angle formed 
* The chalk formation is here selected for the establishment oft' e following positions, from 
its very marked features, and from the facts on which they are founded, having been first re¬ 
marked on the chalk coasts of France and England. But '.he argument applied with equal 
force to all other secondary formations, acted upon by the erosion of the sea. 
