394 APPENDIX. No. IV. 



by the side of a ravine or deep watercourse on the 

 southern face of the same elevation. I have no doubt 

 but that they were in situ. 



I am well aware that the question of light in the 

 Arctic seas will be disposed of by some geologists, who 

 will remind us that the saurians, and probably the 

 ammonites, were endowed with a complicated optical 

 apparatus, rendering them capable of using their eyes, 

 not only for the distinct vision of objects differing 

 greatly in distance, but also of using them, under widely 

 difiering conditions of light and darkness; and I readily 

 admit the force of such observations. 



But what are we to say as to the question of tem- 

 perature ? It was certainly necessary for an ammonite 

 to have a sea free from ice, on which to float and bask 

 in the pale rays of the Arctic sun ; and therefore I 

 claim a temperature for those seas, at least similar to 

 that which now jjrevails in the British Islands : and 

 I may add that the ammonite, from its habits, was 

 essentially dependent on the temperature of the air, as 

 well as on that of the water. 



There is at present a diiiference of 49°'5 F. between 

 the mean annual temperature of Point Wilkie and 

 Dublin ; and if this change of temperature be supposed 

 to be caused by a change of the relative positions of 

 land and water, the temperature of Dublin, or of some 

 place on the same parallel of latitude, must be supposed 

 to be raised to 99°-5 F. ; while the temperature of the 

 thermal equator will exceed 124° — a temperature only 

 a few degi'ees below that requisite to boil an egg ! I 

 reject, without scruple, a theory that requires such a 

 result, which must be considered as a minimum ; as it 

 is probable that the ammonite required a finer climate 

 than that of Britain for the full enjoyment of his exist- 

 ence. 



The theory of central heat, also, appears to me to be 

 open to the same objection, as a mode of explaining 



