37 
HALL65. 
STRUCTURAL AND DYNAMICAL GEOLOGY. 
66^ (together with those in Hall 
66) Illustrate the materials of the earth’s crust and the pro- 
of change which they undergo. They also illustrate 
many striking phenomena met with in the study of the earth’s 
eTarC^Sogy"' ^henom- 
=.11 !•— Dendrites— arborescent impressions on rocks of 
all kinds, which have often the beauty of a drawing They arc 
produced by the deposition of oxides of iron or manganele on 
spread!”” ^°"^aining these minerals have 
Cave products, including stalactites and stalagmites from 
various caves, together with gypsum, epsom salts and otherT” 
?nrbafite””tc. 
Specimens illustrating metamorphism, which may be pro- 
duced by pressure, as where chalk is changed to limestone or 
y chemical changes, as where pyroxene alters to serpentine 
Cementation, illustrated by specimens of coquina of various 
sSation.^'*''’ <^°nglornerates varying in degree of con- 
Stratified structure. Well illustrated by numerous speci- 
mens of sandstone from the Black Hills, the colors of which 
bring out the strata clearly. Faults, produced by rock move- 
Te altmutr^^ 
lb. Illustrated by lavas and scoriae. Where 
the cdls have become subsequently filled with mineral matter, 
amygaaloidal structure is produced. 
Specimens illustrating effects of erosion by wind and wa- 
ter also stages and forms of rock weathering. Ripple marked 
Z -“ •”'* «< peffeci.® sri„ 
showing „„d crack, and rain drop,. "Slickenaid.d” aurfaca. 
Specimens illustrating glacial action, including glaciated peb- 
?“.n‘S or? ‘‘’= »' nUJcr, N. 
localities. Rock surfaces planed and striated by 
g cial movement. Similar specimens from regions of modem 
