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planets. Sir Charles Lyell has lately Induced the Astronomer Royal (Pro- 

 fessor Airy) to make calculations in order to determine exactly how long it ia 

 since the last high eccentricity of the earth's orbit occurred. He did so, and 

 he found that the last period of the earth's greatest eccentricity happened 

 210,067 years ago. A further calculation for past and future ages, made for 

 Sir Charles Lyell by another great mathematician, Mr. doll, arrived at the 

 same general result. It is enough at this time to state briefly that he proves the 

 fact of the existence of a glacial epoch to which the earth has last been subjected, 

 and that it had had previously a tropical climate. Taking into consideration all 

 the co-operating causes, he shows that the degree of the eccentricity of the earth's 

 orbit varies as it approaches its extremes at different times, on a calculation for 

 a million of years preceding the present century and for a million of years 

 to come. Permit me to refer you for further particulars to this most 

 interesting table in Sir Charles Lyell's great work, which may be safely said, 

 geologically speaking, to be the work of the dpy. 



Taking, therefore, a wide and general view of the subject, we find on one 

 hand the wonderful evidence afforded by our vast coal- fields, of a vegetation 

 considered by most geologists to be tropical ; the remains in deep-seated rocks 

 of animals that now only live in tropical climates ; making Geology tell us that 

 at some very remote period the temperature in these latitudes was tropical 

 On the other hand, the surface marks on the earth ; the deep grooves fiom 

 glacial friction on our mountain sides ; the drifts with shells of Artie species 

 of animals ; the presence of strange boulders, &c. ; gives equal proof of an Arctic 

 or Glacial temperature, at a much more recent period. Astronomy now comea 

 with its calculations — whose exactitude at every eclipse never ceases to be a 

 wonder— and tells us, point blank, that it was so, and in the order, moreover, 

 that Geology points out. The earth's climate varies from one extreme to the 

 other — Tropical and Artie. It had last the Artie temperature, and is now again 

 gradually approaching a Tropical climate. The extremes are 233,980 years apart. 



We can see the exact effect of a glacial climate at work in our own day. 

 In the St. Lawrence, between latitudes 47° and 49°, the frost is so intense that 

 during the short period of low water a dense sheet of ice is formed, which, on 

 each return of the tide, is lifted up, broken, and thrown into heaps. As the 

 tide recedes again, the packed ice is exposed to a temperature of 30° below zero, 

 and all frozen together with the adjacent boulders — to be increased again and 

 again as the tides throw up fresh ice, and to be cemented again as they recede, 

 until at length the high tides return with a warmer temperature and the whole 

 mass is swept away together. The light specific gravity of the ice enabling it 

 to lift and float the largest boulders with ease. In this way one single boulder 

 was carried away in 1837, that had been used as a surveying station. It was, 

 therefore, well known; it contained about 1,500 cubic feet, and weighed 120 

 tons. 



Such boulders are very common not only in the neighbouiing county of 

 Shropshire and Great Britain generally, but throughout Europe. Masses of 



