744A REPORT—1899, 
neighbour on the south, and finally out into the Vale of York. On the retreat of 
the ice some of the streams fell back through gapsin the moraine into the old 
valleys, leaving the extramorainic channels as practically dry gorges. One of 
these, Cayton Gill, was three miles long, and its excayation involved the removal 
by stream action of nearly three million tons of rock. 
7. On the Origin of Lateral Moraines and Rock Trains. 
By J. Lomas, A.2.0.8., F.GS, 
In dealing with the accumulations of fraymentary materials associated with 
glaciers it is necessary to distinguish between deposits which are stationary and 
the débris riding on, or moving with the ice. 
The latter, reviving a term used by Rendu, will be referred to as ‘ rock trains,’ 
and the meaning of ‘moraines’ will be restricted to stationary deposits, either 
lateral or terminal. 
Lateral moraines are not necessary adjuncts to glaciers. Their distribution, 
which appears capricious, really conforms to a well-defined law. In glaciers with 
a straight course, they are feebly, if at all, developed, whereas those moving 
through winding channels have lateral moraines developed in their concave bends. 
The débris carried by a glacier either in the ice or on the surface gradually works 
towards the side in such places where motion is retarded and carrying power 
reduced. In this respect they conform exactly to the action of rivers which 
deposit material in their inner bends. 
Rock trains may appear suddenly in the middle of a glacier or at the junction 
of two streams. The first are undoubtedly caused by the erosion of sub-glacial 
spurs or crags. Those formed at the point of union of two glaciers are usually 
regarded as being formed by the joining together of two lateral rock trains. 
There are cases, however, where rock trains are formed at the junctions of 
glaciers, and no lateral rock trains fringe the tributary glaciers. In front of the 
rocky islands or spurs which separate the glaciers at the point of confluence, a 
hollow is always seen in which a lakelet often exists. This is the counterpart of 
the hollow on the down-stream side of a river after passing under a bridge 
supported by piers. 
Objects carried by rivers tend to accumulate in this hollow, and may linger 
there a long time before they join the main current and get carried away. 
Thus rock trains may be formed by débris being thrust out of glaciers at 
similar places where motion is small, In these instances the fragments are 
probably torn off under the ice from the flanks of the dividing spurs, and they 
may be compared with those originating in the middle of a glacier. 
8. Note on the Origin of Flint. By Proressor W. J. Sotzas, F.R.S. 
The first stage was the conversion of the calcareous remains of the organisms 
of the chalk into silica. The siliceous foraminifera and coccolithes so produced 
were cemented by a deposition of silica into white flint, and this by a further 
deposit of silica became converted into black flint, just as snow might be trans- 
formed into compact ice. This had beenshown by the authorin 1880. The source 
of the silica might be looked for in the remains of siliceous organisms such as 
sponge spicules, and Professor Sollas said he was now able to bring positive proof 
of the original existence of abundant spicules in the chalk which were now repre- 
sented by hollow casts to the extent sometimes of 8 per cent. of the rock. 
9. Calcareous Confetti and Oolitic Structure. By H. J. Jounston-Lavis, 
M.D., D.Ch., F.G4.S. 
The older geologists, unaided by the microscope, considered oolitic granules as 
concretionary bodies, as they did also pisolites and other spherical bodies found in 
sedimentary deposits. 
