sign climbed the nearest outstanding spur of the plateau. 
Made a sketch looking up the Gibbon and Madison, nil timber 
but a few parks, etc. (see sketch). 
The upper 300 to 400 feet of the plateau is composed 
of a coarse, massive , grayish and yellow grayish light 
trachyte (see specimen) It was very difficult to get a 
specimen. Nothing of cabinet shape could be procured near 
the top. For 300 feet nearly the yielding massive rock 
weathers in round forms with' the slope end is only partially 
covered by the disintegrated rock which rolls down the 
slopes as coarse sand. 600 feet by seem to be very like 
the top rock but in the lower part there are evidently much 
more compact layers (see specimen) The 400 or 600 feet from 
near the base to the middle of the Slope consists of compact 
sometimes almost shaly reddish trachyte, finer grained than 
that above, (see specimen) 1 the base and near the hot 
springs there are large masses of reddish coarse grained 
somewhat spheralitic porphyry (see specimen) the relations 
of which to the superior rock I could not see. It is probably 
beneath them but It seems very probable that this section 
is ntt continuous --that the trachytes lie in somewhat 
irregular masses. The red porphyry of the base seems to 
run higher above. In returning from the Gibbon to camp I 
observed only trachyte similar in a general way to those of 
the plateau. There are no good outcrops excepting along 
the Madison. Mr. Eckles * party had come in during the day. 
