340 WHITMAN CROSS 
rapidly developing science of paleontology. In his opinion 
fossils were not well enough known, as to their kinds or their 
distribution, to be used as factors in classifying rocks as to 
their geological position. He says, however, that he looks for- 
ward to the time ‘‘when.a system of organic mineralogy will be 
formed.” 
With regard to his system Macculloch remarks: 
The classification is simple; aJl rocks being referred to a primary and a 
secondary class, and a smaller division being formed of those which are 
found in both. The substances which cannot be referred to the latter class» 
from their more recent origin are considered separately in an appendix , and 
a similar expedient is adopted for the volcanic rocks. 
“Primary’’ means to Macculloch anterior in date to the sec- 
ondary; and “secondary” means later than the primary. Each 
class is divided into two divisions, the Stratified and the Unstrati- 
fica sithvese subdivisions,” remarks the author, ‘‘ have not 
yet been introduced into any of the arrangements of rocks, they 
will each require some explanation.” 
The result of Macculloch’s scheme is expressed in the fol- 
lowing tabular arrangement of rocks: 
PRIMARY CLASS. 
Unstratified. 
Granite. 
Stratified. 
Gneiss. Red sandstone. 
Micaceous schist. Argillaceous schist. 
Chlorite schist. Diallage rock. 
Talcose schist. Limestone. 
Hornblende schist. Serpentine. 
Actinolite schist. Compact feldspar. 
Quartz rock. 
SECONDARY CLASS. 
Stratified. 
Lowest (red) sandstone, Limestone. 
Superior sandstones. Shales. 
Unstratified. 
Overlying (and venous) rocks. Pitchstone. 
