324 THE AGE OF THE 



however, is about twelve times as large as that now forming, 

 and would appear, therefore, on the same data, to indicate 

 an antiquity of more than one hundred thousand years. 



In his " Travels in North America/' Sir C. Lyell has en- 

 deavoured to estimate the age of the Mississippi delta, in the 

 following manner : " Dr. Kiddle/' he says, " communicated 

 to me, at New Orleans, the result of a series of experiments 

 which he had made to ascertain the proportion of sediment 

 contained in the waters of the Mississippi. He concluded 

 that the mean annual amount of solid matter was to the 

 water as -r^Vr *& weight, or about 3 ' in volume. Since 

 that period he has made another series of experiments, and 

 his tables show that the quantity of mud held in suspension, 

 increases regularly with the increased height and velocity of 

 the stream. On the whole, comparing the flood season with 

 that of clearest water, his experiments, continued down to 

 1849, give an average annual quantity of solid matter some- 

 what less than his first estimate, but not varying materially 

 from it. From these observations, and those of Dr. Car- 

 penter and Mr. Forskey (an eminent engineer, to whom I 

 have before alluded), on the average width, depth, and 

 velocity of the Mississippi, the mean annual discharge of 

 water and sediment were deduced. I then assumed 528 feet, 

 or the tenth of a mile, as the probable thickness of the 

 deposit of mud and sand in the delta ; founding my conjec- 

 ture chiefly on the depth of the Gulf of Mexico between the 

 southern point of Florida and the Balize, which equals, on 

 an average, one hundred fathoms, and partly on some 

 borings, six hundred feet deep, in the delta near Lake Pont- 

 chartrain, north of New Orleans, in which the bottom of the 

 alluvial matter is said not to have been reached. The area 

 of the delta being about 13,600 square statute miles, and the 

 quantity of solid matter annually brought down by the river 

 3,702,758,400 cubic feet, it must have taken 67,000 years 



