ERRATA. 



P. 252, Une 9, for 3000 read 6000. 



P. ^2, line W, for 500 read 1000. 



P. 253, Une 22, /or 5 feet and 1-lOth read 5710 feet. 



M the foot of Plate XI., for 3000 reafZ 6000; mieZ/or 500 read 1000. 



