Table Mountain, near Golden, Colorado. 453 
Table Mountain is situated upon the plain, twelve miles west 
of Denver, although it approaches so near to the abruptly 
rising foot: hills, composed of Archaean schists, that the inter- 
vening space is scarcely more than a mile in width. Within 
this space, however, are exposed the upturned edges of strata of 
the Trias, Jura, and Creta aceous, including the coal- bearing 
horizon of the Laramie formation ; dipping very pens! cast 
Table Mountain owes its existence to a sheet, or rather 
most parts, to two sheets of basalt, which have in a measure 
protected the underlying strata from erosion. Through that 
agency the upturned strata adjacent have been de nuded until 
a valley several hundred feet deep has resulted, separating 
Table Mountain tect the foot-hills. 
The horizontal strata of Table Mountain seem at first sight 
markedly unconformable with those so near by, but this ap- 
pearance is due to the location of this valley of érosion directly 
in the shar wings In other places the conformability is dis- 
tinctly show 
Opposite the mountain, Clear Creek issues from the foot-hills 
and has cut a gorge directly through it, forming what are 
known as North and South Table Mountains. On the banks 
of the creek, behind the mountain, is situated the town of 
Golden. : 
The mountain is a plateau or mesa of not more than four to 
five square miles in area, with an average elevation above the 
bed of Clear Creek of about 700 feet. 
The source of the basalt is in certain dykes situated to the 
and to the south-southeast. The lower sheet averages 
one hundred to one hundred and fifteen feet i” thickness, and 
— me 8 structure of a stream which has flowed upon the 
Of the second sheet, et the mass p 
remains, and its thickness, as well as the pact! extension of 
sheets, can only be a matter of conjecture 
neeeion basalt of —_— simple composition ; rather coarsely 
erystalline in its massive parts, and in the porous with a ground- 
mass which becomes finer-grained as it a ie cianhta: < pet contact 
or the surface. A glassy base, a- much devitrified was for- 
merly present in the porous par 
In the cavities of the upper paves of the lower sheet are 
