On the Fall of Blvers. 



305 



The first, the Ordnance Map, forms the basis of the other 

 three. By comparing the Index Map with the Ordnance 

 Map itself, the scale of which is ten times larger, the figures 

 shew that the windings of the river in the Index Map disap- 

 pear to such a degree as to give a decrease of 13*3 miles for 

 a length of 81*8 miles, or 16-3 per cent. ; and so a map on a 

 scale 25 times smaller gives a decrease of 23-6 per cent., and 

 a map on a scale 42 times smaller 29-1 per cent., — that is, 

 measuring off the length of a river in a map of a scale of 42 

 miles to 1 inch, the results, however carefully measured, are 

 nearly one-third too small. 



Thus with regard to the Jordan, although not a meander- 

 ing river, and forming almost a straight line from the Lake 

 of Tiberias to the Dead Sea, yet the few bendings and wind- 

 ings of the river, when taken into account, give it a length 

 of 80 English miles,* which is 11 miles longer than Professor 

 rtobinson's statement of 60 geogi-aphical miles. The 14'3 feet 

 of fall per mile which he thus calculates, will be i*educed by 

 the 80 English miles to 12-3 feet. And I have no doubt 

 that when the course of the Jordan is thoroughly explored, 

 it will exhibit a still greater development, and the rate of 

 fall will be still more reduced. f 



The fall of a river influences in part the velocity or force 



* According to Kobinson's r.fap, in his IJiblical Researches. 



t The .Jordan, as appears from Lieut. Molyneux's account, is extremely 

 winding in its course ; the American expedition under Captain Ijynch found 

 that it serpentines 200 miles, and the fact confirms Afr Petermann's argu- 

 ment. — Editor of Journal of Geographical Society. 



