68 
CHALK FORMATION, 
Chalk also occurs in Ireland, Spain, Denmark, 
Sweden, Germany, and Poland.* 
Tlie thickness of the chalk formation varies con- 
siderably in different parts of its course. Near 
Royston, it attains an elevation above the sea of 
481 feet; south of Dunstable, it is 994 feet; 
south of Shaftesbury, 941 feet; between Lewes, in 
Sussex, and Alton, in Hampshire, various parts of 
the range rise to the lieight of between 800 and 
900 feet ; and between Alton and Dover, between 
700 and 800 feet.f In the Sussex range, Ditcli- 
ling Beacon, which is the highest point, is 856 
feet above the level of the sea. 
* Dr. Berger, Geological Transactions, vol. i. p. 14. 
It is supposed that the white chalk does not exist in North 
America, although the discovery of extensive beds of marl and sand, 
in which the same genera of fossil shells prevail as in the chalk form- 
ation of Europe, leaves no doubt that these deposits belong to the 
Cretaceous group. To Dr. S. G. Morton, Secretary to the Academy 
of Natural Sciences of Philadelphia, science is indebted for this im- 
portant and highly interesting discovery. This gentleman has figured 
and described, in Professor Silliman’s American Journal of Science, 
Belemnites, Hamites, Nautili, Ammonites, Echini, &c. which an Eu- 
ropean geologist would immediately recognise as inhabitants of the chalk. 
The specimens in my collection, and for which I am indebted to the 
liberality of Dr. Morton, leave no doubt on the subject. The fossils 
from the limestone superimposed on the marls of New Jersey more 
closely resemble those of Maestricht; there are more littoral shells, and 
fewer pehigic, than in the inferior beds. It is much to be desired that 
Dr. Morton should fovour the world with a more particular account of 
his invaluable researches. Since the above was written. Mi-. Constable, 
of Dover’s Green, near Reigate, has obliged me with an extract from 
his journal made during a tour through North America many years 
since, in which he mentions having observed white chalk in the wilder- 
ness in Alabama. Mr. Constable’s account is so interesting, that I have 
transmitted it to America, in the hope that Dr. Morton will be able to 
examine the locality, and determine the question. 
f Plullips’s Outlines, 2d edition, IS 16. 
