410 GLACIAL PERIOD, WITH REFERENCE TO THE ANTIQUITY OF MAN. 



times ; and of an interglacial land-period in England there were 

 the clearest possible proofs. 



Mr. Topley referred to the relative condition of land now and 

 fifteen hundred years ago, which, he thought, must be of conse- 

 quence in this discussion. From the remains of Roman works we 

 might safely conclude that the physical condition of the country was 

 practically unchanged since that date ; the fords of the Roman 

 roads are often still in use, and no appreciable amount of valley- 

 erosion has taken place in 1500 years. Under these circumstances 

 he thought that we could not suppose such great changes as we 

 know to have occurred could have taken place in only six or eight 

 times that period. 



The President suggested that Prof. Prestwich was not by any 

 means the first person to lay down fixed terms of years for the 

 duration and date of the Glacial period ; he found very definite terms 

 laid down by other writers, and merely indicated reasons why these 

 should be greatly reduced. 



The Author did not attempt to fix actual definite terms of years, 

 but only to show that we must not unhesitatingly accept such large 

 measures of time, especially when based, as they were, upon an assumed 

 and unproved necessity. He objected to remain in that state of 

 ignorance with reference to time which some of the speakers seemed 

 to find quite satisfactory. He referred to the observations of the 

 Danish observers on the Greenland ice, as furnishing us with certain 

 definite time-results, the application of which might be expected to 

 help the question. It was a simple rule-of-three sum. If the 

 Alpine data were supposed to accord with terms of 80,000 and 

 160,000 years, what are the numbers which should accord with the 

 Greenland data? It is impossible to contend that it would make 

 no difference, which would be the conclusion implied by the obser- 

 vations of some of the speakers. 



