TRANSACTIONS OF SECTION Q. 359 
grown by a network of roots and rootlets of millions of plants, which bind 
together the small particles and protect them against wind and running water. 
In arid regions, where the rain is not sufficient to form perennial rivers, 
and where the vegetation forms isolated patches in the barren country, every 
particle of soft or disintegrated rock is quickly taken away by the wind or the 
occasional rainfall. Therefore the general denudation of the land is very 
powerful. The Egyptian monuments, exposed during 4,000 years to the disinte- 
erating and denuding powers of the desert, offer beautiful examples of the 
different kinds of dry disintegration, and many of them show very clearly also 
the transporting effect of the wind. 
3. The Climatic Conditions of the Karly Pre-Cambrian. 
By Professor A. P. Coneman, F.R.S. 
Our knowledge of the later Pre-Cambrian permits us to speak of desert 
conditions in the Keweenawan or Torridonian and of an ice age followed by a 
cool climate in the Huronian, but little evidence has been given as to earlier 
climates. Recent work in Canada shows that the Sudbury series, of Pre- 
Laurentian age and very much older than the Huronian, includes all types of 
sediments, often well enough preserved to show cross bedding, ripple marks, and 
annual layers indicating the change of seasons. They must have been formed 
near the margin of a continent where granites weathered under a cool and 
moist climate. They seem to be delta materials deposited by great rivers. 
The highly metamorphosed sediments of the still older Grenville and 
Keewatin series (Lewisian?) have lost their original structures, but the gneisses, 
quartzites, ‘and marbles must have been clay, sand, and limestone in the 
beginning, and the graphite may have originated in plants. Land surfaces must 
have been attacked by water and air to produce these materials, and there is no 
evidence that the climate was hot. These are the earliest-known formations, so 
that air and water worked in the usual way at the beginning of recorded 
geological time. 
4. Victorian Graptolites. By T. S. Hany, M.A., D.Sc. 
The Silurian and Ordovician graptolite-bearing rocks of Victoria occupy 
about 20,000 square miles, and over a hundred species have been recorded. 
Very little is known of the Silurian. The Ordovician is divided into Upper 
and Lower, but probably represents a continuous series. The Upper is charac- 
terised by the presence of Dicranograptidea. No zonal work has been done in 
the field, though collections yielding about fifty recorded species have been made. 
Four divisions are recognised in the Lower Ordovician, namely, Darriwillian, 
Castlemainian, Bendigonian, and Lancefieldian, at the base. There are several 
subdivisions of these formations. The characters were briefly indicated in 
the ‘Geological Magazine’ by the author in 1899. Subsequent work by T. 8. 
Hart, F.G.S., at Daylesford has confirmed the sequence established. Large 
collections made by the Survey at many localities have somewhat extended our 
knowledge of the fauna and its distribution, but without adding any features 
of great importance. 
The Upper Ordovician ranges north from Eastern Victoria for 300 miles 
into New South Wales. In New Zealand Lancefieldian occurs at Preservation 
Inlet, and two Castlemaine zones occur as well. It is probable that the Victorian 
sequence, and not. the British as stated, will be found. 
Broadly, the sequence of Australian graptolites agrees with the European, 
but in details is closer to that of New York, as Ruedemann has pointed out. 
The important differences in the range of Didymograptus bifidus, D. caduceus, 
D. nicholsoni, Loganograptus, Clonograptus rigidus, and some other genera and 
species negative the idea that graptolite zones are world-wide, and as no one 
believes that all genera and species originated in one locality and radiated thence 
this is what we should expect. 
