CONTENTS. XV 
CHAPTER XII. 
Superficial detritus .... 318 
CHAPTER XIII. 
Position and mode of transport of the great northern boulders... 332 
CHAPTER XIV. 
Modern superficial deposits..... 342 
CHAPTER XV. 
LAKE RIDGES. 
Ridge road of Lake Ontario and Lake Erie... 348 
Terraced hills. 352 
Modern lake ridges and beaches. 354 
CHAPTER XVI. 
Muck swamps. 359 
Lake marl and tufa or Travertine... 360 
Discoloration of sands and clays by percolating water.. 361 
CHAPTER XVII. 
Fossil bones of quadrupeds. 362 
CHAPTER XVIII. 
Modern action of rivers; Freezing of water in river channels... 368 
CHAPTER XIX. 
Waterfalls. 377 
CHAPTER XX. 
Niagara Falls, its past, present, and prospective condition...... 383 
Trigonometrical survey and map of Niagara Falls... 402 
