X907.] AND MOUNTAIN FORMATION. 383 



" A volcano is a pin-prick in the earth's surface and it serves to relieve 

 the local pressure by permitting the escape of steam and molten rock; but 

 an earthquake is produced in most cases by a sudden fracture of the solid 

 substructure of a large region, and as the great mass of material slips into 

 a new position, the shock causes the crust of the earth to shiver from pole 

 to pole. These dislocations are naturally most frequent in regions where 

 mountain ranges are apparently still being squeezed up — where rocky folds 

 are still being bent into shape, as in the Himalayas, and off the west coast 

 of North and South America, and the North of Japan. Regions of greatest 

 instability of the earth's crust are, in fact, found chiefly along the margins 

 of continents or tablelands which rise suddenly to considerable heights above 

 oceanic or other plains. Comparatively few earthquakes have their origin 

 near to volcanoes, and the general belief that all great earthquakes are due 

 to volcanic eruptions is not supported by evidence derived from observations." 



Professor Gregory thus says that earthquakes occur chiefly where 

 mountain formation is in progress, but he is entirely silent as to 

 the cause of mountain formation itself. Unfortunately he blindly 

 accepts the traditional doctrine of the secular cooling and contrac- 

 tion of the globe, which is shown to be devoid of any sound 

 physical basis. 



§ II. An Estimate of the Relationship between the Expansion and 

 Contraction of the Globe. — It is well known that at intervals the 

 sea coasts are elevated by the world-shaking earthquakes to which 

 they are subjected. It is difficult to form an estimate of the total 

 area thus uplifted, but for a preliminary estimate we may take it 

 to have an average extent of 200 miles square, which would about 

 correspond to the phenomena witnessed in the greatest earthquakes. 

 There would be 4,924, or roughly 5,000, such areas on the surface 

 of the entire globe. According to Milne's estimate of 60 world- 

 shaking earthquakes per annum, there would be 120,000 in the 

 2,000 years which have elapsed since the century before the begin- 

 ning of our era. 



Now an examination of great earthquakes shows that about 

 one in four is accompanied by a sensible elevation of the dis- 

 turbed area. If there are in all 5,000 such areas to raise, and 

 30,000 disturbances for raising them, it follows that on the average, 

 when all areas are affected alike, each part would be raised 6 times 

 in 2,000 years. An average raise of 2 feet is not extreme, and 

 this gives an expansion of the total surface of the globe amounting 



