No. 5.] DAWSON — LIGNITE FORMATIONS. 2'4^' 



miles west of Red River, and the chief exposure is something- 

 less than a mile south of the line, and in the Territory of Mon- 

 tana. A seam of lignite coal no less than 18 feet thick there 

 crops out. The section, including this lignite, is as follows, m. 

 descending order : 



1. Surface soil 1 foot in. 



2. Drift (quartzite pebbles) 1 " 6 



3. Yellowish and grey stratified saudy 



clays 9 " 



4. Lignite " 9 



5. Brown, banded clays, with plants and 



some crystalline gypsum 5 " 



6. Lignite (weathering soft) 10 " 



7. Lignite (hard and compact) 8 " 



8. Soft grey sandstone 5 " 



40 3 



The laminated clays of bed 5 when first exposed show plant 

 remains in great perfection ; even the delicate fronds of ferns^ 

 which are here unusually common, showing every detail of their 

 form. On drying, however, the clay becomes cracked and fis- 

 sured, and it is with difficulty that the impressions can be pre- 

 served. The association of selenite crystals, isolated or in groups^ 

 with the clays and arenaceous clays holding plant remains, is~ 

 very constant. 



The upper part of the lignite bed weathers soft and forms a 

 steep slope. The lower part is hard, and being divided by ver- 

 tical jointage planes, like many true coals, falls into the stream 

 in great rectangular blocks, and presents a vertical face. 



The plants associated with the lignite beds are very numerous: 

 in species, but have not yet been fully examined. Manyy?a^ 

 and se(/^e-like leaves occur. At least two kinds of Ferns are 

 represented — a Sphenoptcrls and an Onodea apparently identi- 

 cal with 0. sensiOilis, a form still living. There are also twigs 

 of several coniferous trees, including a cedar, Thuja interrupta 

 of Newberry, and apparently species of Seqiioia and Taxus ; 

 and from the microscopic structure of the lignites it would 

 appear that most of them are made up of woods of this kind.. 

 Leaves of a great many species of deciduous trees also occur, and. 

 are generally full grown, and appear to have fallen in the order 

 of nature, and at the change of the season, and floated quietly 

 out into the great lakes, in the fine silty deposits of which they 

 have been preserved. Pojmlus, Salix, Ulmns, Platanus^ and 



