Dr. J. W. Evans—Geological Maps. Al 
interrupted lines and the intercalation of dots. Further subdivisions 
can he distinguished by the spacing of the shading, variations in the 
number of dots, and other devices. In the Kainozoic, the Hocene and 
Oligocene are shown by diagonal crosses and the Miocene and 
Pliocene by upright crosses. The Kocene and Oligocene can be 
distinguished by the opposite or alternating arrangement respectively 
of the crosses and a similar distinction can be made between the 
Miocene and Pliocene. Here, again, numerous means can be devised 
by variations in the forms and relations of the crosses to express 
minor divisions. 
Passage beds, or those in which the outcrops of different strata 
are too much involved to be separately mapped, may be indicated 
by a combination of two shadings. The usual symbolic shading for 
lithological characters can also be combined with this method of 
shading. 
The occurrence of volcanic rocks is indicated by a thickening of 
the shading. Intrusive rocks are shown in black, or if it is desired to 
express their age this may be effected by the same shading as that 
employed for sedimentary rocks but reversed, that is to say in white 
on black. 
