BOTANY OF I, A SALLE COUNTY. 3 



the Illinois, Fox and Big 1 Vermillion rivers. These 

 sections are of very unequal size, that east of the Fox 

 and north of the Illinois being 1 the smallest, while the 

 northwest and southeast sections are much larger 

 than the southwestern one. 



These sections differ in some points, depending- upon 

 the geological structure of the country. We will 

 therefore take a brief survey of the g-eology of the 

 county. 



Geology. Beginning* at the north line of the state 

 we find thick beds of a grayish yellow, rather soft 

 limestone (the same as quarried at Joliet), called the 

 Niag-ara limestone because it is of the same ag-e (it 

 contains the same fossils) as that forming- the upper 

 part of the precipice over which the Niag-ara river 

 flows at the Falls. It appears at Osweg-o, Kendall 

 County, on the Fox River Valley Division of the Chi- 

 cago, Burlington & Quincy Railway. It dips, sinks, 

 toward the south and near the north line of I/a Salle 

 County the carboniferous beds, often called coal meas- 

 ures appear as a thin bed, thickening- as we g-o south. 

 A little north of Ottawa coal is found, and this forma- 

 tion is not more than twenty feet thick. Going- south 

 it still thickens and, at Streator, is 210 feet thick, 

 while at La 'Salle it is much thicker. Coal is seldom 

 found more than a mile and a half north of the north 

 bluff of the Illinois valley, but except the floor of the 

 valley from Ottawa west, it covers all the County to 

 the south. Over much of this area, much more than 

 half, but one bed of coal exists, but about Streator 

 two workable beds are found and at L/a Salle three. 

 The coal beds are desig-nated by numbers from the 

 lowest upward, the lowest, and consequently the old- 

 est, being numbered I. This does not occur in the 

 County. Numbers II, III, IV, V, VI. VII, VIII, 



