IfOTES AKD QUEllIES. 
149 
allimiim." The glaciers still occupied for a long time tlie deepest Yalleys, 
and prevented their being filled with alluvial deposits ; then they melted, and 
the Lakes Maggiore, Como, and Leeco, Orta and Iseo were formed. This 
was the fourth and last ijart of the glacial epoch, which gradually merged 
into the present period. 
NOTES AND QUERIES. 
CoNVEESiois' OF Chalk INTO Maeble. — Gustav Eose has been making 
new experiments on the deportment of carbonate of lime at high tempera- 
tures, both with and without fluxes ;* and, from their results, he has arrived 
at the conclusion that rhombohedral carbonate of lime is never a direct 
product. 
According to the experiments of Sir James Hall, made in 1804, this has 
been directly produced when chalk and compact limestone were exposed 
to a high temperature under great pressure. 
Hall's experiment has therefore been repeated by MM. Eose and Sie- 
mans. A gun-barrel was charged with dry elutriated chalk, rammed into 
a compact mass, and the gun-barrel then hermetically sealed at both ends, 
and exposed to the heat of one of M. Siemans' gas-furnaces. During the 
experiment the gun-barrel sprung, and in the crack there appeared a faint 
blue flame, evidently of carbonic oxide. The gun-baiTel was then removed 
from the furnace, and on opening it the chalk was found converted into a 
light bluish-white coherent mass, slightly lustrous on the fracture, and with 
cracks running through the whole. The surface was covered with a snow- 
white, earth}', well-defined crust, and the cracks were lined with white 
earthy particles ; these, as well as the crust, were composed of caustic lime. 
The compact mass, however, proved, on examination, to be unchanged 
in chemical properties ; and in physical properties, though seemingly 
changed, when examined under the microscope, it showed the same small 
globules, and identically the same properties, as the uniguited amorphous 
chalk. Although somewhat more coherent, the chalk was not materially 
altered, and in nowise converted into crystalline calcite. Another experi- 
ment was made with fragments of rhombohedral calc-spar, but was also in- 
terrupted by the rupture of the gun-barrel. 
M. Rose considers, from these experiments, that chalk or compact lime- 
stone cannot be converted into crystalline limestone or calc-spar by expo- 
sure to a high temperature in closed vessels ; and, as a general fact, that 
rhombohedral carbonate of lim^ is not formed in the dry way. He also 
observes that, on comparing accurately the description of Hall's experi- 
ments and Bucholz's observations incidentally made in the production 
of caustic lime from chalk, probably they obtained results similar to his 
own, and that the slightly coherent, but otherwise unaltered mass, was er- 
roneously considered to be crystalline marble. But what is most singular 
is, that notwithstanding Hall's experiment has been quoted and use made 
of it, not only in explaining geological phenomena, but in serving as 
the foundation of theories, it was never repeated or confirmed : and the 
experiments of M. Eose show it at least to have been hasty, although we 
do not think M. Eose's have been as complete nor as long continued as 
* For an account of ITcrr Rose's experiments, see Transactions of the Berlin Aca- 
demy ; roggeudorf, Aunalen, c. xi. 156 ; and Sillimau's Journal, xxxii. 112. 
