LETTER TO THE SECRETARY. 13 



sheet shall be two and one-half degrees in longitude and one and one-fourth degrees 

 in latitude. The 112th meridian shall be taken as the standard from which the maps 

 aTe to be projected in an easterly and westerly direction, and the 38th parallel as the 

 standard from which they shall be projected in a northerly and southerly direction ; 

 these lines forming the division-lines between the atlas-sheets adjacent thereunto. 



Third. Maps or charts of the second or " special " class may be constructed on other 

 scales and embracing other areas, whenever it shall be found necessary for the purpose 

 of properly representing mining-districts, mineral, agricultural, pasture, or timber 

 lands, or for other special purposes. 



At the end of the next season, if suitable appropriations are made by 

 Congress for the purpose, the survey will have completed the most rug- 

 ged and mountainous portion of our continent, lying between meridians 

 104° 30' and 109° 30' and parallels 40° 45' and 40° 30'. This will form 

 an atlas of six sheets, each comprising about 11,500 square miles, or a 

 total of about 69,000 square miles. These maps are intended to express 

 not only the topographical features, but the geological also ; and, in 

 accordance with the directions of the Secretary of the Interior, these 

 charts will indicate the areas of grass, timber, and mineral lands, and 

 such other country as may be found to be susceptible of cultivation by 

 irrigation. 



Numerous special maps of the mining-regions, isolated mountain- 

 ranges, and other localities remarkable for their complicated geological 

 structure, have been prepared on different scales. Much more of this 

 detailed study of interesting localities will be made when the final maps 

 are completed. Collections of great value were made in geology and 

 mineralogy, all of which will be reported on in due time. 



Since the publication of the annual report for 1873, several volumes 

 have appeared in connection with the survey, which must be regarded 

 as of great value. Volume II of the quarto series, by Professor Cope, 

 on the " Cretaceous Vertebrata of the Western Territories", contains 

 304 pages text, with 57 plates. Volume VI of the quarto series, on the 

 " Cretaceous Flora of the Dakota Group", by Leo Lesquereux, constitutes 

 an original contribution to the vegetable paleontology of America, and 

 will prove very useful in fixing a most important geological horizon. 

 It contains 136 pages, with 30 plates. Much new material has come to 

 hand since the publication of that memoir, a portion of which will be 

 found in this report. A third edition of the " List of Elevations" and a 

 second edition of the " Catalogue of Photographs" have been printed to 

 supply the demand for the miscellaneous publications. The most import- 

 ant volume of the miscellaneous series, however, is the "Birds of the North- 

 west", by Dr. Elliott Coues, which comprises over eight hundred closely- 

 printed octavo pages. Much of the text is written in popular style, 

 treating of the habits, or, as it were, the domestic life, of the birds ; and 

 on this account the demand for it among onr people has been unusually 

 great. Although it does not pretend to be a general work on the orni- 

 thology of the Western Territories, it contains a more or less complete 

 descriptive list of four-fifths of the birds of the United States. 



