Treeless Areas of the Northwest — Leiberg. 147 



not an acre of ground can be found for long distances, but has 

 dozens of these fossil tree stumps protruding from the ground. 

 These stumps are transformed into the hardest kind of silica, and 

 the actions of the winds and the driving dust and sand have put 

 ;iu unapproachable polish on theiM. 



It may be remarked in passing that it is a rather novel and 

 strange arrangement, that the settler upon these prairies should^ 

 in order to clear his farm, be obliged to pull the stumps of trees 

 that flourished perhaps 50,000 years ago. Yet such, in many lo- 

 calities, is the fact. 



Occasionally, a huge trunk is found silicified as it fell. 



The rocks and clayey subsoil abound with leaf impressions^ 

 and at times remains referable to the fruit or seeds are found. 



The leaves enclosed in the rocks have usually been trans- 

 formed into a black carbonaceous substance, which crumbles quick- 

 ly upon exposure to the air, but the outline of the leaf, as well as^ 

 the minutest features, are found perfectly preserved when first 

 exposed. In the clay, nothing but the impressions of the leaf 

 commonly remain, but every detail is plainly marked. 



Where the rocks or the clays have been subjected to heat by 

 the burning of the underlying lignite beds, the fossil stumps have 

 melted into huge fantastic humps, and the contained leaf impres- 

 sions have baked into the clay, leaving almost indestructible im- 

 prints. 



Upon investigation, it has been found that the species of 

 trees that made up these ancient forests were in a great measure 

 composed of species that yet have living representatives in our 

 own country. 



Among genera to which these fossil trees have been referred 

 may be mentioned the oak, birch, poplar, willow, beech, sycamore, 

 sassafras, magnolia, sumach, tulip tree and many others, showing 

 how closely the then existing sylva was related to our own. The 

 abundance and size of the fossil remains indicate a luxuriance and 

 vigor of growth not found now except on the western slope of the 

 continent. Many of the trees must have been of immense size. 

 On the bluffs bordering the valley of the Green river in Stark 

 county, Dak., I have measured stumps that showed a diameter of 

 fully twelve feet. The heavy beds of lignite, occurring every- 

 where, and of which the upper beds, at least, are composed almost 



