SOUTHERN CALIFORNIA ACADEMY OF SCIENCES 23 
knowledge, because of the disturbance of imaginary relations between 
accepted numbers and certain numbers made of sacred significance by 
treasured tradition. 
The Chairman stated that Jupiter’s surface is surrounded to the 
depth of several ‘thousand miles by a luminous vapor of considerable 
density, which is suposed to shut out the light and heat of the sun from 
the body of the planet. 
The intense luminosity of Jupiter is due to the reflecting power of 
this enveloping vapor, and is greatest towards the center of the disk. 
This is opposite to the fact touching the brilliancy of the face of the 
moon, which is greatest toward the edge of the disk. 
The discussion drifted into a consideration of the causes and move- 
ments of earthly tides. 
Mr. Dozier gave a blackboard illustration of the prime causes of tides 
and their variation, showing them to be due to the attractive forces of 
the sun and the moon and the centrifugal forces generated by the revolu- 
tions of earth and sun and moon about common centers of revolution. 
Much interest was manifested in all phases of the discussion by the 
appreciative members present. 
MELVILLE DOZIER, Secretary. 
3. Section of Botany. 
(No meeting was held in January.) 
4. Section of Geology. 
January meeting. 
The Geological Section of the Academy met at the State Normal 
School Building, Monday, January 23, at 8 p. m. Chairman George W. 
Parsons called the meeting to order and introduced Prof. W. C. Menden- 
hall, of the U. S. Geological Survey, as the speaker of the evening. 
He took for his subject ‘‘The United States Geological Survey and 
Its Work.’’ He stated that many years ago the Government was the 
pioneer in the survey of the topographical and geological status of the 
western States and Territories. He gave a vivid description of Major 
Powell’s exploration of the Grand Canyon of the Colorado. He also 
stated that the different Government surveys were united under one head 
March 3, 1879, by Act of Congress, and that numerous correct topographi- 
eal and geological maps, which would be of great assistance to the geolo- 
gist and miner, had been made at great expense. 
As to the value of those maps, he referred to the constant use made 
of them in the districts of Cripple Creek, the Comstock lode, the Butte 
region, the iron fields of Michigan, and in the Tonopah district. 
He also reviewed the studies made in the measurements of water 
courses, and announced that the contract for the Yuma Dam would prob- 
ably be let sometime next month; a project which will irrigate 107,000 
acres. 
The speaker gave reminiscences of his own explorations in Alaska in 
1895 and 1896, including his experience on the Yukon river in an open 
canoe. He described the manner of obtaining the altitude of Mt. 
MeKinley, which is somewhere between 20,300 feet and 20,500 feet. 
The lecture was well attended and full of interest. 
Questions were asked and answered. 
G. MAJOR TABER, Secretary. 
