Note 1485 — Chapter VI
Reading edition
The place of Niagara Falls in geological history, by G. K. Gilbert, of the U. S. Govt. Surv., in the Proc. Amer. Assoc., Ibid. p. 223; Geology of Minnesota [final report], by N. H. Winchell and Warren Upham, vol. i. p. 337 (St. Paul, 1888).