in Reply to Mr. Beke. 253 



mate which made the distance to Babylon 206 miles, and thus 

 the addition to the delta since Alexander the Great 245, com- 

 bined with the " assuming a construction" (of the distance to 

 Charax) " to be more correct," which, without all those me- 

 tamorphoses, would bring it to worse than nothing ; and now, 

 " if we attach no importance to Pliny's express reference to 

 the extraordinarily rapid growth of the land in the Persian 

 Gulf," we may, from the formation of new land within the 

 Adriatic, "at all events be permitted to calculate" this growth 

 in the Persian Gulf to be at least from 2 to 20 miles in 2000 

 years, that is, at the utmost, about 24 for the same period ! 



The whole geological evidence now offered, reduced to a 

 plainer form, amounts to little more than the latter inference. 

 Mr. Beke, however, supposes the claims of the Euphrates and 

 Tigris to a large delta to be stronger than that of the Italian 

 rivers, from the far greater extent of country through which 

 the former and their tributaries sweep. But any such rule 

 must, I apprehend, be received with very large qualifications. 

 In the instance cited, certainly the fact lies exactly the other 

 way. The great source of the silt of rivers is the high grounds, 

 from which the looser matters, set free by rivulets and other 

 causes, descend to the lowlands — the higher of course the 

 greater the quantity, — and that again increased by the momen- 

 tum it gains in its headlong passage to the plains. But what 

 lowlands can be placed more favourably for an increase to 

 their level by such an agency, than those about the shallow 

 head of the almost tideless Adriatic, little removed from the 

 encl of a declivity from such a storehouse of detritus as the 

 Alps? 



The source whence the evidence is taken, and the authority 

 adduced, is the able work of Mr. Lyell. But we are imme- 

 diately there taught the utter unfitness of the comparison. 

 " The Adriatic," (says Mr. Lyell,) "presents a great combina- 

 tion of circumstances favourable to the rapid formation of 

 deltas*;" and yet the 20 miles at Adria, the maximum of this 

 increase, is. in great measure attributable, not to geological 

 causes, but to mere human labour, for again we find " that since 

 the system of embankment became general, the rate of en- 

 croachment of the new land on the Adriatic is said to have been 

 greatly accelerated." M. Pronyf, whose investigations seem 

 to have led to this knowledge, says that in the 12th century, 

 before, by the same ordinary means, a passage had been 

 opened at the north bank of the Po, Adria was distant from 

 the sea but 9000 or 10,000 metres, in 1600 its distance was 



* Lyell's Geology, first edit., vol. i. p. 235. 



f De la Beche's Geological Manual, third edit., p. 70. 



