
392 STRUCTURAL AND FIELD GEOLOGY 
dried and desiccated, would in like manner tend to drift 
before the wind. In some such way, deposits originally of 
glacial and fluvio-glacial origin have been rearranged and 
redistributed by zolian action. This conclusion is supported 
by the occurrence in the loess of the remains of a true Steppe- 
fauna—embracing jerboas, pouched marmots, tailless hare, 
little hamster rat, and many other forms which are the 
common denizens to-day of the Steppes of Eastern Russia 
and Western Siberia. 
Loess may be described as a fine calcareous loam, consist- 
ing of an admixture of minute particles of quartz and clay. 
The percentage of calcium carbonate varies, often reaching 
or even exceeding 30 per cent. Its light red or yellowish 
colour is due to the presence of iron-oxide. Small percentages 
of magnesia, potash, soda, and phosphoric acid are usually 
present. Loess thus yields an excellent soil, the regions 
covered by it being noted for their great fertility. 

