432 
THE GEOLOGIST. 
of those operations which have effected the marked changes between 
their actual and their original positions. 
Then follow the various propositions: — 1st. "That most of these 
heds must have descended very slowly after their formation, beneath the level 
at which they were deposited; " and as an auxiliary to this proposition, 
"That every area of long-continued deposition must have leen an area of 
sloio continuous depression. Tliat hy far the greater portion of the 
carth^s surface wldch now constitutes dry land must have been raised 
above the level at u-lbicli it was origincdhj formed.'^ 
In many cases, such descending movement must demonstrably have 
preceded the ascending. For on reference to the preceding diagram 
(fig. 8) it is easily seen that the edges of the strata which are, in a 
geological sense, the lowest in the series, are actually found at the 
greatest height above the sea-level, — often as much as 8,000 to 10,000 
feet, and even to 15,000, as in the Himalaya mountains ; but these 
same strata, if they have a sufficient aggregate thickness of strata 
above them belonging to the higher part of the series, must, from 
what has been already proved, have gradually descended from their 
original position during the deposition of the superincumbent beds. 
Mr. Hopkins anticipates the very natural question: "But what 
physical causes can be assigned of sufficient mechanical energy to 
produce these mighty movements?" and replies that modern volcanic 
eruptions indicate the former existence of adequate power in the intu- 
mescence of fluid lava produced by the expansion of elastic gases 
within it. 
( To he coniinued.) 
POREIGN COllEESPONDENCE. 
By Db. T. L. PnirsoN, of Paris. 
Tyrilifcfous lignite, and its applications — A Diamond which has tttrned 
out to be a Topaz — The metal Cerium and its compounds — IFatcrs of 
the Bay of Vulcano at Santorino — Talccontology in Southern Russia — 
JSrrata. 
At the last meeting of the Socic'te Impcriale d' Horticulture, at Paris, M, 
Millot-Brule, an agriculturist, presented to the members of this insti- 
tution a dark-coloured earth, which he had employed with success, he 
stated, against the attacks of grubs, snails, &c., in gardens or planta- 
tions. By scattering a small quantity of this earth around any plant, 
the approach of slugs, or the larva of insects, &c., was rendered im- 
possible. This was proved by experiment before the meeting, by placing 
some slugs and larvae of cockchafers upon a damp plate of glass and 
surrounding them with a circle of the black earth. Not a single one 
could make its escape, and pass out of the circle ; and when the earth 
was sprinkled upon them, the animals soon died. Experiments were 
also tried, with similar success, upon the cryptogamic vegetation which 
constitutes the disease of tlie grape. Vines tbat had suffered remarkably 
from the ravages of the Oidium Tucleri were restored to health when 
