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brouht here by its waves ; they have been floated here upon ice, and deposited 

 on this common at that distant time, when it was covered by the icy waves of an 

 Arctic sea. It is not to be expected that this view will be believed all at once. 

 It is only a few weeks since that I met with such fierce opposition to it 

 from a well-educated gentleman here, that I will now take some pains to prove 

 to you, at any rate, its possibility. 



Sir Charles Lyell, one of the greatest living philosophers, proves, on 

 evidence it is impossible to resist, that the glacial period lasted for thousands 

 of years, and yet that it was of so modern a geological date as to belong almost 

 to the time, when shells of the same species existed, as are now found in higher 

 latitudes. It is the geographical range only that is changed. An artic fauna 

 was then enabled by the low prevailing temperature to invade the now tem- 

 perate latitude. Thus marine shells of living artic species have been found ia 

 some of the glacial drift of Scotland, which do not, and could not, exist in the 

 present tempeiature of her seas. The inference is unavoidable, that tbe earth s 

 surface has experienced great changes of climate since it has been inhabited by 

 animal life and it is quite possible that such changes can be reconciled with the 

 existing order of nature. We must not regard the climate of England as a type 

 of the temperature which all countries placed under the same latitude enjoy. 

 Isothermal zones— zones of equal warmth— are neither parallel to the equator 

 nor to each other. The mean annual temperature may be the same in two places 

 with very different climates, for the seasons may be nearly uniform, or they may 

 be violently contrasted. The causes which co-operate to produce these effects 

 are as various now as formerly, such as the geographical distribution of land and 

 ■water, ocean currents, the precession of the equinoxes, the eccentricity of the 

 earth's orbit, &c., &c. Let us consider for a few moments the last cause only, 

 which in itself proves enough for our purpose. 



At present the earth's orbit is becoming year after year more circular, and as 

 a natural consequence its seasons warmer and more equable in temperature. In 

 23,913 years from the present time it will be as circular as it ever can be, or in 

 other words the earth's orbit will then have its minimum of eccentricity. After 

 this time its orbit will begin again to increase at the same slow rate. These 

 perturbations are caused chiefly by the attraction of the planets Jupiter, Saturn, 

 Venus, and Mars, and their extent, astronomers have been able to calculate. The 

 extreme range of this eccentricity amounts to 14J millions of miles. At the 

 present time it is three millions of miles, and this difference, though it may 

 seem small, would involve a loss of no less than one-fifth of the entire heat de- 

 rived from the Sun, for the heat would vary inversely, as the squares of the 

 distance from the Sun. The consequence of the loss of one- fifth of the tem- 

 perature in that hemisphere in which winter occurs, when the earth is farthest 

 from the Sun, would be, that all the moisture in the air would fall as snow, 

 and the lessened heat of summer would not be able to remove the winter's ice. 

 The earth's axis of rotation is now at an angle of 23° 28' to the plane of the 

 ecliptic, and it varies about 48 seconds per centuiy, owing to the action of the 



