A VERY OLD MASTEE 111 



Every now and again, geological evidence goes to show 

 us, a long cold spell occurs in the northern or southern 

 hemisphere. During these long cold spells the ice cap at 

 the poles increases largely, till it spreads over a great part 

 of what are now the temperate regions of the globe, and 

 makes ice a mere drug in the market as far south as Covent 

 Garden or the Halles at Paris. During the greatest 

 extension of this ice sheet in the last glacial epoch, in fact, 

 all England except a small south-western corner (about 

 Torquay and Bournemouth) was completely covered by 

 one enormous mass of glaciers, as is still the case with 

 almost the whole of Greenland. The ice sheet, grinding 

 slowly over the hills and rocks, smoothed and polished and 

 striated their surfaces in many places till they resembled 

 the roches moiLtonn&es similarly ground down in our own 

 day by the moving ice rivers of Chamouni and Grindelwald. 

 Now, since these great glaciations have occurred at various 

 intervals in the world's past history, they must depend 

 upon some frequently recurring cause. Such a cause, 

 therefore, Dr. Croll began ingeniously to hunt about for. 



He found it at last in the eccentricity of the earth's 

 orbit. This world of ours, though usually steady enough 

 in its movements, is at times decidedly eccentric. Not 

 that I mean to impute to our old and exceedingly respect- 

 able planet any occasional aberrations of intellect, or still 

 less of morals (such as might be expected from Mars and 

 Venus) ; the word is here to be accepted strictly in its 

 scientific or Pickwickian sense as implying merely an 

 irregularity of movement, a slight wobbling out of the 

 established path, a deviation from exact circularity. 

 Owing to a combination of astronomical revolutions, the 

 precession of the equinoxes and the motion of the aphelion 

 (I am not going to explain them here ; the names alone 

 will be quite sufficient for most people ; they will take the 



