90. How may we identify formations in separate districts? How is the interrupted and partial distribution of strata to be accounted for? 91. In what respect do the fossils in younger strata differ from those in older strata? What general proof can be adduced to shew that species have become gradually extinct? 92. Give an instance how fossils prove changes of climate in the past. What is supposed to be the cause of great cosmical changes of climate? Describe Mr Croll's theory of cosmical changes of climate. 93. What is the test of _superposition_? Mention another test of the relative age of strata. 94. Name the four great divisions under which the fossiliferous rocks are arranged. 95. Name the Primary or Palæozoic formations. What are the principal kinds of fossils found in the Old Red Sandstone? Which formation is the chief repository of coal in Britain? 96. In what other formations do coals occur? In which formation do the oldest known mammals occur? Name the Secondary formations. 97. Name the Tertiary formations. What kind of climate characterised the northern hemisphere at the beginning of Pleistocene times? What kinds of climate would appear from the evidence to have chiefly prevailed in Primary, Secondary, and Tertiary ages? Have we any trace of frigid conditions during these ages? What is the growing opinion with regard to the climatic conditions during the glacial period of Pleistocene times? THE END. Edinburgh: Printed by W. & R. Chambers. * * * * * * * Transcriber's Notes The only minor correction that was noted in converting this document from a printed version into an electronic version was an unpaired parenthesis on the first line of the Title Page. * * * * * * *