ANCIENT LIGNITE BEACHES ON THE SOURIS. 293 



men of lignite was seen near the mouth of Plum Creek, 

 where we camped on the 29th ; it was a water- worn 

 rounded boulder. 



After leaving the Blue Hills no trees or shrubs of any 

 description were seen until we arrived at Plum Creek. 

 On low points in the Souris valley some fine oak, elm, 

 balsam poplar, and aspen are found for the first twenty 

 miles. The guelder rose is common on the ravines, wild 

 prairie roses abundant, snowberry and two varieties of 

 cherry of frequent occurrence, as well as woodbine, wild 

 convolvulus, and hop, but for a distance of twelve miles 

 west of the Blue Hills the country is treeless on both sides 

 of the river, and the drift of small depth. 



A little beyond Plum or Snake Creek we found nume- 

 rous pebbles and boulders of lignite; and with a view to 

 ascertain whether the lignite existed in situ, an excavation 

 was made in the bank of the river and the stratification 

 for a depth of twenty-five feet exposed. The last outcrop 

 of the cretaceous shales was observed about three miles 

 east of the bank where this trial was made. A few hours' 

 labour revealed five old beaches, probably of a former 

 lake. These beaches were composed of sand and boulders 

 of lignite from the size of a hen's egg to one foot in 

 diameter. No fragment of lignite was found which did 

 not possess a rounded or spheroidal form and a roughly 

 polished or worn surface. An abundant supply was easily 

 obtained for a fire which was soon made on the bank ; a 

 strong sulphurous odour was emitted from the iron pyrites 

 in the lignite, and some boulders when broken open ex- 

 hibited streaks and small particles of a resinous substance 

 like amber. 



The excavation exposed the section which is shown 

 in the woodcut on the next page. 



The low hills about Plum Creek are sand dunes, and on 



u 3 



