REPORT OF ASSISTANT SECRETARY. 183 



shown in tlie accompauyiug illustratiou (PL 57), tlie Iciieud beiug 

 repioduced below, as it is too illegible in the illustration: 



U. S. XATIOXAI. MUSKUM 



DEPARTMENT OI' GEOLOOY 



MODEL OF THE | UNITED STATES 



showing tho theoretical restoration of the | Ancient Ice-Slieet | at the stage of 

 the (Uacial Period | following the Main Silt Epoch. | Constructed from data fur- 

 nished by T. C. Chamberlain aud associates | of the U.S. Geological Suryey; 

 the outline of the ice follows | the outer terminal moraine next north of the main 

 slit deposits, and | probably does not represent a strictly synchronous stage 

 throughout, as later | advances of the ice at some points overrode earlier ones, 

 making it difficult | to trace a perfectly synchronous line. The slope of the sur- 

 face of the ice is | based on an adaptation of that of (ireenland, as given by 

 Nausen. | 



The scale of the model is 1 inch to 40 miles. | It shows the correct curvature 

 at sea-level, and is a section of a globe | 16i feet in diameter; elevation and 

 depression above and below sea-level exaggerated five times. 



At the beginning of the fiscal year the curator was in southwest 

 Missouri searching for materials to illustrate cave phenomena. This 

 work was interrupted by leave of absence from July 8 to August 1, to 

 be resumed again at a later date. On August IS the curator returned 

 to Washington. The materials collected during these trips are noted 

 under the head of "important accessions." Mr.W. H. Kewhall, assist- 

 ant, made in November a trip to Weyer's and Fcmntain caves in Vir- 

 ginia, and obtained a fine series of i)roducts from these sources, M'hich 

 are also mentioned under the head of accessions. Our thanks are due 

 to the managers of these caverns, as well as to those of Luray, Mam- 

 moth, Wyandotte, ^Marengo, Percy and llobertson's, for the lively inter- 

 est manifested and the assistance afforded in procuriug as fine a series 

 as possible both for the Columbian Exi)ositi(»n and for the Museum. 

 We are also greatly indebted for assistance of a high order to Prof. 

 W.O.Crosby, of the Massachusetts Instituteof Technology, and to Mr. 

 F. W. Crosby, of this city. Prof. Crosby was instrumental in i^rocuring 

 a large i)roportion of our series of glacial products, and to the enthusi- 

 asm of Mr. F. W. Crosby we owe a large and exceptionally fine series of 

 Sicilian sulphurs and associated rocks and minerals, volcanic bombs 

 from Lipari, and other materials elsewhere note<l. From April 15 to 

 May 15 the curator was in Chicago, eugagcd in the work of installing 

 the exhibit there. 



Below is given a list of the more im[)ortant accessions of the year: 



A series of typical iron ores froui S;iuti;ig(). Cuba. Gift of the Sigua Ir<ui Com- 

 pany. 



A collection of asphalts and assorted roc i<s from Trinidad, (iift of Mr. Clidord 

 Richardson. 



A collection of rocks and ores from Texas. Gift of W. H. Streeruwitz. 



A collection of glacial materials made by Prof. W. O. Crosby for tlit^ World's 

 Columbian Exposition. 



