78 Notes on Foreign Geology and Mineralogy. 
methods by which a figure representing the mean density of our 
globe may be obtained ; it will be sufficient to remind our readers 
that the experiments formerly made at Schehallien lead to the figure 
4-718, those at Mont Cenis 4:95, both of which were pendulum- 
experiments, while the results obtained by the torsion-balance of 
Cavendish have been, in the hands of various philosophers, 5°448, 
5440, 5-660, 5:°577. It will be remembered, also, that the recent 
pendulum-experiments of Airy (1854) in the Harton coal-mine gave 
the figure 6°566,* with a probable error of 0-182. In a recent 
number of the Journal Cosmos (12 Mai, 1864), M. Babinet, of the 
French Institute, has published an ingenious paper, entitled ‘ Note 
sur le calcul de l’expérience de Cavendish, relative 4 la masse et a la 
densité moyenne de la terre,’ in which the number arrived at is 
5:50. We see, therefore, that experiments made with the torsion- 
balance coincide very much better than the pendulum-experiments 
hitherto made. 
M. Valenciennes has lately presented to the French Academy the 
tooth of a fossil Crocodile of enormous dimensions. ‘This fossil 
tooth was discovered in the Oolite formation of Poitiers ; it is coni- 
eal, regularly rounded off, and slightly curved; it is no less than 
54 inches long, and is covered with black striated enamel. In order 
to give some idea of the enormous size of this crocodile, compared 
with that of the species now living upon the globe, the veteran pro- 
fessor exhibited at the same time a tooth of the largest crocodile yet 
met with, taken from the anatomical collection of the Jardin des 
Plantes, when the members of the Academy found themselves 
obliged to exclaim with Moliére, 
“T1é! monsieur, un petit mulet !” 
The remains of several great Saurians have been recently dis- 
covered in this Oolite of Poitiers by M. Raynal, and deposited by 
him in the Museum of that town. Professor Raynal promises a paper 
upon them, in which the new Crocodile will be described under the 
name of Crocodilus formido. It is impossible to confound this 
species with the Megalosaurus, the teeth of which have saw-edged 
summits, and are altogether distinct from those of a Crocodile. 
REVIEWS. 
tbh a 
Cours DE PALKONTOLOGIE STRATIGRAPHIQUE. Par M. A.p’ ARCHIAC. 
Premiére Année. 2 vols. pp. 491 and pp. 616. With 3 Tables. 
Paris, F. Savy, 1864. 
TUDENTS of Paleontology have long stood in need of a book 
which should occupy in that science the place held in Geology 
by Lyell’s ‘Principles; for though ‘Manuals,’ ‘Elements,’ and 
* Corrected by Haughton, 5-48.—EKprr. 
+ The tooth of Pliosaurus grandis, in the British Museum, from the Kim- 
meridge Clay of Dorset, measures 12 inches in length !—Eprr. 
