91 
period, or, otherwise stated, that it was not a depressed area receiving 
marine or other types of sediment. 
As to the age of the formation of the granite, the exeursion only 
gave indications that it was earlier than the observed Tertiary, but other 
evidence would suggest that it is at least pre-Cretaceous. As to how 
much earlier than the Cretaceous the granite was formed has not, as 
far as I know at present, been definitely determined. Certain rocks in- 
truded by the granite farther north yielded fossils that have been re- 
ferred to the Triassic. The intrusion may be as late as the late Jurassic, 
and thus correspond to extensive granite intrusions that are found in 
the Sierra Nevada. 
At intervals the read climbed to more prominent divides in passing 
from one creek valley to another, and a broader extent of country could 
be seen. To the east of Campo and before the descent into the Imperial 
valley the country is especially open and affords good general views of 
the Summit region. A moderate climb to a hill not far from the road 
broadens the horizon still more. 
The topography of the summit region proved to be of considerable 
interest. There is no sierra, no prominent or striking peaks rising high 
above their surroundings, no wild or rugged mountain scenery. The 
relief is quite moderate, and in distant views the hills appear to unite 
to give a remarkably even summit surface or plateau effect, below which 
lie the commonly shallow and open mountain valleys, and into whieh 
an occasional canyon is incised along the border of the summit region. 
The small section of the party that was fated to stay at Warren’s 
ranch over night, climbed up a small granite knob in the early evening. 
Our eyes were alternately drawn to the western horizon by the beauti- 
ful sunset, and towards the eastern horizon by the rising full moon. 
Tt was the 13th of the month, and our automobile had broken down and 
disconnected us from the main party, but I am sure that any misgiv- 
ings that we may have had were thoroughly dispelled and replaced by 
a feeling of pleasure that such a remarkable scene on such a wonderful 
night had been made available to us. The general plateau effect was 
strikingly brought out, and it was this very feature of the summit 
region that made possible the simultaneous presentation to our view of 
sunset and full moon. 
The dominant character of the summit region, I believe to be the 
result of the long period of erosion above mentioned which removed the 
covering from the granitic rocks. The indications are that this region 
was thereby reduced to a very moderate or low relief, that, in terms of 
geographic cycle, the topography became at least that of advanced ma- 
turity, possibly of general peneplaination. It seems probable that this 
