CARBONIFEROUS LIMESTONES OF IOWA. 101 
land. The prairie-sod, matted and deep-rooted, usually requires from six to eight 
yoke of oxen effectually to break it up. 
The future farms of Iowa, large, level, and unbroken by stump or other obstruc- 
tion, will afford an excellent field for the introduction of mowing and reaping 
machines, and other improved implements calculated to save the labour of the 
husbandman ; and which, in new countries reclaimed from the forest, can scarcely 
be employed until the first generation shall have passed away. 
The curious and remarkably symmetrical mound-like form of some of the outliers 
of the Carboniferous Limestone on the northeastern side of the basin, beyond the Forks 
of the lowa, are so extraordinary, that they have been deemed worthy of illustration. 
OUTLIER OF CARBONIFEROUS LIMESTONE, IOWA RIVER. 
SECTION VI. 
THEIR LOCAL DETAILS. 
CaRBoniFEROuS Rocks or THE Iowa Rrver.—After leaving Township 81 north, 
Range 8 west, no rocks were seen in place near the river for about fifty miles in a 
direct line, and nearly double that distance by the river, which is very tortuous in 
its course. The deep alluvial and drift deposits effectually conceal the strata on 
which they rest. It is only from the angular fragments of chert occasionally seen 
strewn on the elevated ground, that any clue is obtained to their age; this mineral 
