114 
POPULAR SCIENCE EEYIEW, 
employing a mixture of 20 parts of saltpetre, 5 parts of sulphur, 4 parts 
of sulphide of cadmium, and 1 part of powdered charcoal, a composition 
is obtained which gives a white flame surrounded by a magnificent blue 
margin. Cadmium is now to be obtained tolerably cheap, being prepared 
as a bi-product in the manufacture of zinc in Belgium. 
LTHOUGII everyone knows that, at a late Geological period, the 
whole of England was icebound, probably few have realized the 
vast duration of the glacial epoch. It is still common in the professor’s 
lecture-room to hear the boulder-day spoken of as “ a great splash”; for 
the idea of cataclysm, beaten back from every other quarter, has at last 
found a stronghold in the drift. Believing, as we do, that causation has 
never been more intense in past time than now, it is with interest we 
notice a little addition to Britain’s glacial history, in a paper by Mr. Smith, 
of Jordan Hill. 
In one of the small Western Isles, called Little Cumbra, consisting of 
Trap, there is an old sea terrace or shore, forty feet above the present sea- 
level, and from it the rock has been worn and removed at least one 
hundred feet. Now, quite near the shore, and far from this old cliff, are 
some large boulders, also of Trap, and one of them is split. Split blocks 
are common in Switzerland, and appear to have become fractured by 
falling, — generally from the escarpments of ice-terminating glaciers. 
Hence, as this block is so distant as to preclude the possibility of its 
having fallen from any neighbouring height, there are no other expla- 
nations of its position and breakage than that it either fell from an ice- 
escarpment at the time the forty-feet terrace was formed, or that it was 
dropped from an ice-raft drifting therefrom. 
These blocks rest on a surface which had previously been smoothed and 
furrowed by ice, and the glacial stria:, still to be seen, extend down the 
shore and dip under the sea.* And, therefore, this conclusion becomes 
evident, that, since the land has had its present level, the total amount of 
wearing away of the shore has not exceeded a small fraction of an inch, 
whereas the old glacial period lasted so long that during the time Cumbra 
was under its influence, hundreds of feet were removed. It must not be 
forgotten, however, that in the olden time the cliff was buffeted and worn 
by the more potent agency of ice, while now it is merely lashed by the 
sea ; but, whatever allowance may be made for this difference, the con- 
viction must still remain that, relatively to the great drift period, 
“ This fine old world of ours is but a child 
Yet in the go-cart.” 
An important piece of evidence, tending to show that the drift was no 
rapid denudation but a slowly-formed deposit, is the occurrence in it of 
shells which lived at the time. These have been found in various parts of 
our islands, but few lists are more interesting than one given by the Rev. 
GEOLOGY AND PAL/EONTOLOGY. 
* Similar glacial stria? are still to be seen on Snowdon. 
