“SS 
TIPU GIGACILALIL, VAAILILIEVGS) (HE WIE, WL SSMS, SULT 747 
RATE OF FALL OF THE PREGLACIAL ROCK FLOOR AND THE PRES- 
ENT MISSISSIPPI FROM FORT SNELLING, MINNESOTA, TO THE 
GULF OF MEXICO. 
Dist. Low High Fall per Fall per Rock 
Location Miles Water Water Mile Mile Floor 
A.T. A.T. L. W. H. W A. T. 
Ft Ft In. In Ft. 
IP, Smmellhinner, MGI, 5 00000 ) O86! Ne pulierael lPpwaena sicvaulyeccicosssveutse 486* 
Sit Pawel, MMVI so05 c000 G0 6 683 702 GROOM | te sais 4837 
Lake City, Minn.......... 55 O5Si Stee Sey AS i Pilisccace Sante 495? 
La, Crosse, WilSs000000 0006 68 628 643 5.30 5.75 5043 
Prairie du Chien, Wis. .... 60 604 623 4.80 4.00 4923 
Dubuque, Iowa........... 55 585 607 4.14 3.49 4533 
Saloulla,, WOW ocoe coocnoce 36 572 592 An BB 5.00 429 4 
ton eon oes cps ele 16 566 587 4.50 2.75 465 
Le Claire, lowa (New Ch.). 20 562 576 2.40 6.60 550 
Rock Island, Ill. ie, Che 16 542 560 15.00 12.00 530 
Muscatine, Tlowsen( (New Ch.). 24 531 547 5.50 6.50 506 
Near Wilton, lowa (Old Ch.)}........]... "2 les: onl seamed Paeaebert ereva"llluearaet eaecare 400-5 
Mouth of lowa IRIE o oo0 18 523 539 5-33 Bee 445- 
Burlington, lowa......... 24 S11 527 6.00 6.00 430- 
Ft. Madison, Iowa........ 18 502 518 6.00 6.00 365° 
Neer Milemiaross (OUMC Ele aspen lesen essildnes ue dollsceo Sees loemia do 3747 
Montrose, lowa (New Ch.). 9 500 514 2.66 5-35 490 
Kecokulslowaraneeiciecieeie 12 477 494 23.00 20.00 470 
OmineysVU As ee eepcree 38 458 | 476 6.00 5.68 4138 
lnlaroroullogll, IMI, 2 oo00c00000 17 450 467 5.64 6.35 362 9 
Wowisianias) Mowe sereiee ce 25 437 453 6.24 6.72 380—7° 
Mouth of Illinois River.... 68 403 422 6.00 5 Ay i 
Bellefontaine, Mo......... 7) 402 420+ 0.70 1.40] 2957! 
dase Sits Wows, Wes soo cocc Dil ® 380 414 10.86 2.96+| 284% 
He Carondelet, Mili... ..- 6 377 412 6.00 4.00 330 
Fountain Bluff, Ill......... 100 313 357 7.68 6.60 300 33 
MbNelbess Milles, sca sicrsicte aeteicests 40 201 339 6.60 5.40 2807? 
Cannoawillt4 eae sarareeve vee. 35 270 22K 7.20 6.16 B 
Memphis, Tenn.5 ........ 233 183 218 4.48 Sod Rae 
IMIOWN Oi WHEE 5650000 0000 855 ON ets cisco %c 2.56 By iD Qva Mite Sranences ress 
tN. H. WINCHELL: Amer. Geol., Aug., 1892. 
? Geol. of Minnesota, Vol. IL. p. 17. 
3 CHAMBERLIN and SALISBURY: Sixth An. Rept. U.S. G.S., p. 223. 
4 Data given by W. R. Oake, Ex-Mayor of Sabula. 
>This point is about ten miles from Muscatine and fifty miles from Fulton 
making the old course about the same length as the new one. A well at this point, 
reported by Professor Udden, failed to reach rock at elevation 4oo feet A. T. 
°C. H. GorDoN: Geol. of Iowa, Vol. III., 1893, p. 246. A well one-half mile 
north of Ft. Madison reaches a level about 365 feet A. T. without entering rock. The 
channel may, therefore, be deeper than that shown by the Ft. Madison wells. 
7 Beck’s Artesian Well, Geol. of Iowa, Vol. III., p. 247. 
* Bridge piers rest on a rock shelf 35-40 feet below low water (G. K. Warren). 
° Data concerning channel piers furnished by W. S. Lincoln, Chief Engineer of 
Wabash Railroad, St. Louis, Mo. 
