found in the Oolite Quarries of the Isle of Portland. 401 



period ; the period of the secondary strata from lias to chalk inclusive ; and 

 the period of the tertiary strata above the chalk. 



The plants before us render it probable that the climate of these regions, 

 at the time when the oolites were deposited, was of the same warm tempera- 

 ture with that which produces a large proportion of (he existing Cycadeae. 

 M. Adoiphe Brongniart is also of opinion that it exceeded the temperature of 

 our modern tropics at a still more early period when it maintained the extra- 

 ordinary vegetation of the great coal formation ; and that it was less than 

 tropical, though warmer than it is at present, in the period to which we owe 

 our tertiary strata. To this theory I see much reason to incline, and confi- 

 dently look forward to its future developement in the examination of the Flora 

 of the fossil world, which he is now so actively conducting. 



VOL. II. — SECOND SERIES. 3 G 



