UPHEAVAL AND SUBSIDENCE, 



lusks which lived on their surface ; rivers emptying on the coast 

 became fordable where they had been navigable by small vessels ; 

 well-known anchorages were diminished in depth to a correspond- 

 ing extent, and at different points, shoals now oppose the passage 

 of vessels of large draught where they readily floated before. 



Analogous circumstances occurred in India in 1819; a lull, fifty miles 

 long and sixteen broad, was raised up in the midst of a flat country, barring 

 the course of the Indus. Further to the south, on the contrary, but parallel 

 to the same direction, the country sank, carrying down the village and fort 

 of Sindre, which nevertheless remains standing, half submerged. The 

 eastern mouth of the river became more shallow in many places, and por- 

 tions of its bed which had been fordable suddenly censed to be so. 



The history of all times and of all places furnishes us with facts of exactly 

 the same nature. Everywhere we are told of fissures in the earth, of pro- 

 found chasms, in which cities and even entire countries are swallowed, from 

 which flow mephitic gases, enormous masses of water, sometimes cold, 

 sometimes hot, sometimes even flaming. Also of plains suddenly trans. 

 formed into mountains, of shoals raised in the midst of the ocean, of moun- 

 tains rent and overturned, of mountainous regions, of hundreds of leagues 

 of rocks all at once levelled arid replaced by lakes. Of water-courses 

 changed, swallowed in chasms of the earth ; of lakes which dry up by 

 breaking through their bounds, or suddenly lost in subterraneous conduits, 

 instantaneously formed. In opposition, we also learn of enormous springs 

 producing new streams, suddenly rising through a fissure of a rock, without 

 any knowledge whence the waters come: of thermal springs which have 

 become instantaneously cold ; of others, on the contrary, appearing where 

 they did not exist before. All these phenomena are so many indications of 

 fissures in the earth, which afford new channels to waters which might 

 have circulated there before. 



(>. Relatively to the sea-coasts, these phenomena are often men- 

 tioned by authors in a peculiar manner ; rarely do we see it expli- 

 citly announced, there is an elevation ; but the event is stated in 

 other terms, referring the effect to the most moveable element. In 

 this way authors speak of the sea having retired more or less, leav- 

 ing its bed dry, either permanently or only for an instant : some- 

 times, on the contrary, they mention that the sea suddenly over- 

 flowed more or less elevated coasts. Geologists translate these 

 indications by the term oscillation, if the phenomenon be mo- 

 mentary, and by the terms upheaval, or subsidence of coasts, if it 

 be permanent, because they refer these effects to the solid parts of 

 the globe, and not to the sea, the level of which does not vaiy. 

 Nevertheless it must be borne in mind that, if these transitory phe- 

 nomena may sometimes be attributed to oscillations of the earth, 

 they may also arise from a real impulse communicated to the 

 waters of the sea, and possibly partake of both causes. We 

 know, in fact, that during earthquakes the sea is sometimes vio- 

 lently ao-itated, that its waters, elevated to considerable heights, 

 occasionally make fearful irruptions on the land, advancing and 



6. What is meant by oscillation ? What is meant by upheaval ? What 

 bv subsidence 9 



