72 



REPORT OF THE SECRETARY. 



PaiiiiMiin latifoliniii, L. 

 Paiiicnin inicTocariioii, Miilil. 

 Paiiicuiu diibotomnin, E. 

 Paiiicuin Crns-galli, L. 

 Setaria glaiica, Boauv. 

 Sotaria viiidis, Beaiiv. 

 Erianthus saceharojdes, Mirlix. 

 Andropogon fnsoatus. 

 Andropogon Virgiiiiciis, L. 

 Eqnisotniu liyemaU-, L. 

 Poly podium vulgare, L. 

 Ptt'ris aqnilina, L. 

 Adiaiittiiii ]>pdatnin, L. 

 ANpleiiiiini Trichoiiianos L. 

 Asj)lt'iiiiiiii ebenenni, Ait. 



Asplciiiiiin tlielypteroides, Micbx 

 Aspleniuiii Filix-fu'iiiiua, Bomb. 

 I'begoptcM'i.s bexagouoptcra, Feo. 

 .Aspidinm NovaVioraceuse, Swartz. 

 Aspidiuin Filix-nias, Swartz. 

 Aspidinui acrosticboides, Swartz. 

 Cystopteris fragilis, Benib. 

 Onoclea seusibili. 

 Dickson ia i)ilosinscnla, Walld. 

 Botrycbinm ternatuin. Swartz, var. obli- 



quniii, Miblo. 

 Botrycbinm ternatuin, Swartz, var. dis- 



sectnm, Jlilde. 

 Botrycliinm Virginianiim, Swartz. 

 Lycopodium complanatnm, L. 



GKOLOGY OF THE ZOOLOGICAL PARK. 



A special report npon tbe geology of tbe Park bas been kindly fnrnisbed by Mr. 

 W. J. McOee, geologist to tbe Geological Snrvey. 



'' Tbere is transmitted berewitb a geologically colored map of tbe National Zoolog- 

 ical Park. 



" Except tbat tbe prevailing rock formation is complex in structure and of age n(»t 

 yet definitely determined, the geology of tbe Park is exceedingly simple. Tbe for- 

 mations are: 



Recent Alluvium. 



Pleistocene Columbia loam and gravel. 



Cretaceous (?) Potomac gravel. 



/ Piedmont gneiss. 



Arcliean (?) ) Vein quartz. 



( Steatite. 



"In addition to tbese well cbaracterized formations tbere is a limited variety of 

 re.sidna left on decomposition of rock in place, of torrential or ()verplaceraent depos- 

 its formed by wasb adown slopes, etc. 



"Tbe recent alluvium is confined to the channel and flood plain of Rock Creek. It 

 consists of loam, sand, and gravel partly derived from tbe older formations within 

 the Park, but mainly brought in by Rock Creek from beyond tbe limits of tbat re.ser- 

 vation. These materials arc sometimes irregularly stratified, but again assorted into 

 sheets, sand-ltanks, gravel-bars, and more extended stretches of loam. It sbonld be 

 observed tbat the alluvium area, together with tbe channel meandering tiirougb it, 

 are coterminous with tbe flood plain of Rock Creek, and hence are subject to over- 

 flow during great freshets. 



" The Columbia formation is a deposit of loam, gravel, bowlders, etc., formed dur- 

 ing the first ice invasion of the glacial period. Its age is therefore early Pleistocene. 

 About rivers the formation commonly consists of two members, the upper a homoge- 

 neous loam commonly red or brown in color, and the lower a bed of sand, grave), 

 cobble-stones, and bowlders commonly stained brown by ferric oxide, sometimes 

 stratified, and here and there displaying a peculiar black stain which is mainly fer- 

 ruginous, but has been found to contain a trace of cobalt. Along the rivers of the 

 Middle Atlantic slope the formation is sometimes fashioned into terraces; and some 

 of its best developments in the District of Columbia (from which the name is taken) 

 are terracifomi. In the Park the deposit displays tbe usual division into a superior 

 loam and an inferior bed of coarse materials; and the usual topographic form is as- 

 sumed since tbe deposit is practically confined to the pine-clad terrace or bench north 

 and west of Rock Creek, in the central ])art of the reservation. Tbe formation is in- 

 deed confined to the.se terraces, save tbat an ill-defined and perhaps scarcely contiuu- 



