172 



FARMb:RS' REGISTER 



[No. 3 



lies through much wet ground, being along the 

 bottoms of the Illinois, just under its northern 

 bluff. As these lands are overflowed during the 

 spring-freshets, the level of the canal requires to 

 be considerably raised, and to be guarded by 

 strong embankments. The construction of a ca- 

 nal-basin, at the termination of the canal, with an 

 area of five and a hall' acres, whose boitom is to 

 be considerably elevated above the present level 

 of the bottoai-lands, serves to render this division 

 of the undertaking also very expensive. The 

 cost of the entire canal, as estimated accordinn- to 

 the report of the commissioners, is .§8,654,337; 

 but it is admitted that the estimate is too low, it 

 being generally believed that the work will not be 

 brought to a state of completion under ten millions 

 of dollars. 



The geology of the chief portion of the route 

 above described, is exceedingly simple and uni- 

 form, the great rock formation of the country be- 

 ing the mapiesian limestone; at least, this is the 

 rock from the commencement of the canal, (four 

 miles from Chicago,) nearly to the mouth of the 

 Kankakee. It also re-appears west of the Fox 

 river, as will presently be pointed out, and enjoys 

 a wide distribution probably throughout the whole 

 of Upper Illinois and Wisconsin. A good oppor- 

 tunity for examining its character occurs near 

 Chicago, wiierc the excavations have already 

 been commenced. It here rises quite to the sur- 

 face of the prairie. It is imperfectly stratified, 

 with an evident dip of 10*^ or 15* to the north- 

 west Its color is light grayish- white, with a fre- 

 (juent shade of yellow. It is compact in lextin-e, 

 and often slightly cellular or cavernous — a pecu- 

 liarity which seems to be connected, tor the most 

 part, with the profusion of organic remains exist- 

 ing among its materials at the period of its forma- 

 tion. The following is a brief list of the fossils 

 which fell under my observation at this locality: 

 two species of Orthoccra, a Turbo (one and a half 

 inches in diameter) with a depressed spire; a large 

 species of Pectunculvsl ; a Tercbratuln, (with 

 very prominent ribs, and but (ew in number;) two 

 species of Ammonites; a CaryophyUia, and a I^a- 

 vosites.* Some of the beds are wanting in fossils, 

 and occasionally the rock puts on a shistose or 

 slaty structure, in which case it forms a valuable 

 flagginii-stone, which is already emjiloyed to some 

 extent in Chicago. 



The same rock re-appears in the bed of the Des 

 Plaines, twelve miles from Chicago, on the road 

 to Juliet, as well as near the surface of the prairie at 

 Plainfield. nine miles from Juliet, and very abun- 

 dantly also at this last place. The beds at Plain- 

 field and Juliet, however, are not rich in fossils. 

 The rock is quite close in its structure, and where 

 acted on by the weather, of a yellowish bulF color, 

 much resembling the lithographic stone of Soh- 

 ienhofen, in Bavaria. The quarries at Juliet af- 

 ford it in very even, distinctly stratified layers, 

 whose position is nearly horizontal, their thickness 

 being such as to render it a very valuable buildino- 

 material. 1 noticed one variety of the rock at this 

 place, which had been thrown out in sinkino- a 



* Several of these species I am persuaded are new; 

 but I defer a particidar description of them until I 

 shall obtain an additional supply of specimens, pro- 

 mised me by Dr. Brainard, of Chicago. 



well, the appearance of which was very analogous 

 to that of true dolomite, (the gurhofian variety.) 

 Its color is a grayish-white, wiih a tinge of green ; 

 throughout the masses were crevices and openings, 

 whose walls were lined with transparent crystals 

 of quartz. 



The magnesian limestone continues very abun- 

 danily in the bed of the Des Plaines, below Juliet, 

 and recurs frequently on the road across the prai- 

 rie to Holderman's grove, twelve miles east of Ot- 

 tawa ; after which, no more rock was observed 

 until I reached the bed of Fox river, just above the 

 village of Ottawa. At this point, we strike upon 

 the coal formation. 



Of the existence of formations more recent than 

 the magnesian limestone in this region, my own 

 observation permits me to add nothing, beyond 

 what has already been stated under the head of 

 the lake shore near Chicago. By the kindness, 

 however, of Mr. W. B. Ogden, the mayor of 

 Chicago, and Col. Thornton, president of the 

 board of coiTimissioners lor the canal, I am ena- 

 bled to annex some additional particulars. The 

 excavations for the canal on the wet prairie give 

 the following superficial formations ; one to two 

 feet, black vegetable mould, and two to six feet, 

 yellow, clayey loam, resting on blue clay. On 

 reaching the Des Plaines, the sections give, in 

 the first place, one foot of black mould ; secondly, 

 four feet, yellow sandy clay: thirdly, one and a 

 half feet clean black sand, and lastly, twelve feet 

 "vegetable formations with shells."* 



The occurrence ol' boulders in the rolling prai- 

 rie had often been mentioned to me, under the 

 significant and original appellation bestowed upon 

 them in this region, ol ''lost rocks." Their abun- 

 dance, however, surpassed my expectation. They 

 first attracted attention soon after leaving the 

 twelve-mile house fi-om Chicago, and appeared to 

 form a belt between a quarter and half a mile in 

 width, whose direction wa« north-west and south- 

 east. In crossing this belt, it was uncommon to 

 pass many rods without encountering a boulder. 

 In general, they were rather more than half bu- 

 ried in the soil. They varied in diameter, from 

 ten inches up to three feet, and belonged to the 

 following species of rocks; granite, granitic gneiss, 

 and trap. A iew detached boulders only were no- 

 ticed between this deposit and Ottawa. Soon 

 after leaving this place, however, another band or 

 patch of them was passed. They were here 

 scattered over the Illinois bottoms so plentifully, 

 as to prove objects of no inconsiderable annoyance 

 in the road. Two miles below this locality, like- 

 wise, a number of large masses were seen. 

 Others were occasionally met with south of this 

 point, out upon the rolling prairie, in the direction 

 of Vermilionville. What serves materially to 

 heighten our interest in these boulders is, the con- 

 sideration that they must have been transported 

 over a distance of between two and three hun- 

 dred miles, since the southern shore of Lake Su- 

 perior is the nearest region affording rocks of a 

 similar character, in situ. 



* From the same source, I learn that the magjnesian 

 limestone beneath these deposits often abounds with 

 vertical fissures, filled with clay, from one inch to se- 

 veral feet in breadth. 



