VIII ADVERTISEMENT. 
Under this law the following papers have heen published: 
1. Pumping Water for Irrigation, by Herbert M. Wilson. 1896. 8°. 57 pp. 9 pi. 
2. Irrigation near Phosnix, Arizona, by Arthur P. Davis. 1897. 8°. 97 pp. 31 pi. 
3. Sewage Irrigation, by George W. Rafter. 1897. 8°. 100 pp. 4 pi. 
4. A Reconnoissance in Southeastern Washington, by Israel Cook Russell. 1897. 8°. 96 pp. 7 pi. 
5. Irrigation Practice on the Great Plains, by Elias Branson Cowgill. 1897. 8°. 39 pp. 12 pi. 
6. Underground Waters of Southwestern Kansas, by Erasmus Haworth. 1897. 8°. 65 pp. 12 pi. 
7. Seepage Waters of Northern Utah, by Samuel Fortier. 1897. 8°. 50 pp. 3 pi. 
8. Windmills for Irrigation, by E. C. Murphy. 1897. 8°. 49 pp. 8 pi. 
9. Irrigation near Greeley, Colorado, by David Boyd. 1897. 8°. 90 pp. 21 pi. 
10. Irrigation in Mesilla Valley, New Mexico, by F. C. Barker. 1898. 8°. 51pp. 11 pi. 
11. River Heights for 1896, by Arthur P. Davis. 1897. 8°. 100 pp. 
12. Water Resources of Southeastern Nebraska, by Nelson H. Darton. 1898. 8°. 56 pp. 21 pi. 
13. Irrigation Systems in Texas, by William Ferguson Hutson. 1898. 8°. 67 pp. 10 pi. 
14. New Tests of Certain Pumps and Water-Lifts used in Irrigation, by Ozni P. Hood. 1898. 8°. 
91 pp. 1 pi. 
15. Operations at River Stations, 1897, Part I. 1898. 8°. 100 pp. 
1G. Operations at River Stations, 1897, Part II. 1898. 8°. 101-200 pp. 
17. Irrigation near Bakersfield, California, by C. E. Grunsky. 1898. 8°. 96 pp. 16 pi. 
18. Irrigation near Fresno, California, by C. E. Grunsky. 1898. 8°. 94 pp. 14 pi. 
19. Irrigation near Merced, California, by C. E. Grunsky. 1899. 8°. 59 pp. 11 pi. 
20. Experiments with Windmills, by T. O.Perry. 1899. 8°. 97 pp. 12 pi. 
21. Wells of Northern Indiana,by Frank Leverett. 1899. 8°. 82 pp. 2 pi. 
22. Sewage Irrigation, Part II, by George W. Rafter. 1899. 8°. 100 pp. 7 pi. 
23. Water-right Problems of the Bighorn Mountains, by Elwood Mead. 1899. 8°. 62 pp. 7 pi. 
24. Water Resources of the State of New York, Part I, by George W. Rafter. 1899. 8°. 99 pp. 
13 pi. 
25. Water Resources of the State of New York, Part II, by George W. Rafter. 1899. 8 3 . 101-200 
pp. 12 pi. 
26. Wells of Southern Indiana (Continuation of No. 21), by Frank Leverett. 1899. 8°. 64 pp. 
27. Operations at River Stations for 1898, Part I. 1899. 8°. 100 pp. 
28. Operations at River Stations for 1898, Part II. 1899. 8°. 101-200 pp. 
29. Wells and Windmills in Nebraska, by Erwin H. Barbour. 1899. 8°. 85 pp. 27 pi. 
30. Water Resources of the Lower Peninsula of Michigan, by Alfred C. Lane. 1899. 8°. 97pp. 7 pi. 
In preparation : 
31. Lower Michigan Mineral Waters, by Alfred C. Lane. 
— Water Resources of Porto Rico, by Herbert M. Wilson. 
TOPOGRAPHIC MAP OF THE UNITED STATES. 
When, in 1882, the Geological Survey was directed by law to make a geologic ruap of the United 
States, there was in existence no suitable topographic map to serve as a base for the geologic map. 
The preparation of such a topographic map was therefore immediately begun. About one-fifth of the 
area of the country, excluding Alaska, has now been thus mapped. The map is published in atlas sheets, 
each sheet representing a small quadrangular district, as explained under the next heading. The 
separate sheets are sold at 5 cents each when fewer than 100 copies are purchased, but when they are 
ordered in lots of 100 or more copies, whether of the same sheet or of different sheets, the price is 2 
cents each. The mapi^ed areas are widely scattered, nearly every State being represented. About 
900 sheets have been engraved and printed; they are tabulated by States in the Survey's "List of 
Publications," a pamphlet which may be had on application. 
The map sheets represent a great variety of topographic features, and with the aid of descriptive 
text they can be used to illustrate topographic forms. This has led to the projection of an educational 
series of topographic folios, for use wherever geography is taught in high schools, academies, and 
colleges. Of this series the first folio has been issued, viz : 
1. Physiographic types, by Henry Gannett, 1898, folio, consisting of the following sheets and 4 pages 
of descriptive text: Fargo (N. Dak. -Minn.), a region in youth; Charleston (W. Va.), a region in 
maturity; Caldwell (Kans.), a region in old age; Palmyra (Va.), a rejuvenated region ; Mount Shasta, 
(Cal.), a young volcanic mountain; Eagle (Wis.), moraines; Sun Prairie (Wis.), drnmlins; Donald- 
sonville (La), river flood plains; Boofhbay (Me.), a fiord coast; Atlantic City (N. J.), a barrier-beach 
coast. 
GEOLOGIC ATLAS OF THE UNITED STATES. 
The Geologic Atlas of the United States is the final form of publication of the topographic and 
geologic maps. The atlas is issued in parts, or folios, progressively as the surveys are extended, and 
s designed ultimately to cover the entire country. 
Under the plan adopted the entire area of the country is divided into small rectangular districts 
(designated quadrangles), bounded by certain meridians and parallels. The unit of survey is also the 
