360 
augite-syenite, for at this contact it is observed that the stra- 
tification of the kakortokite gradually disappears, and that the 
rock which comes nearest the contact is completely unstratified, 
whilst instead of horizontal partings vertical pegmatitic segre- 
gations occur parallel to the contact plane. 
Under either hypothesis the recurrence of the processes, 
as expressed in the forty repetitions of the same set of sheets, 
demands some further explanation by an outside source. In the 
interior of the earth any plausible cause for such regular re- 
currence seems very difficult if not impossible to find. At the 
earth’s surface recurrence is generally connected with igneous 
activity, and it may even be said that recurrence is a funda- 
mental character of volcanic outbursts. Recurrence is manifest 
in the stratified structure of every lava plateau at every age, 
and the volcanic rock series of Ilimausak is no exception to 
the rule. 
It does not seem improbable that a large volcanic outburst 
should influence the physical conditions of the subjacent magma 
bodies. In the first place the pressure within the magma re- 
servoirs must vary: an explosive outburst will cause a rapid 
decrease of pressure, and the quiet outflow of lava increas- 
ing the pressure at some places must lessen it at others. 
Secondly, as each eruption causes a considerable loss of heat 
the subterranean temperature will be affected. Thirdly, volcanic 
eruptions may cause movements or currents within the magma 
bodies. All these processes may be assumed to be able to 
modify the rate of magmatic crystallization, and if crystallization 
is in progress concurrently with the volcanic activity, this latter 
condition will probably often be realized. Thus it must be 
admitted as possible that volcanic outbursts under favourable 
conditions may leave a permanent record upon the structure of 
abyssal rocks, and the characteristic feature of such marks 
must be that they are recurrent. 
For the banded kakortokite of the Ilimausak complex the 
