E. W. Hilgard—Geology of the Southwest. 265 
We will now examine the analogical phenomena in the case 
of light. Let fork No. 1, giving 256 vibrations a second, stand 
for 508,730,000,000,000 vibrations a second; which will be the 
number of vibrations made by the ray D, of the spectrum, if 
we cag A 300,000 kilometers per second as the velocity of 
light. Then fork No. 8 will represent 504,750,000,000,000 vibra- 
tions per second; which latter give a wave-length ‘0000048 
millimeter longer than that of D, and belong toa ray removed 
from D,, toward the red end of the spectrum, by eight times 
the distance which separates D, from D, We saw that fork 
No. 8, giving 254 vibrations a second, had to move toward 
the ear with a velocity of 8°784 feet to give the note produced 
by 256 vibrations per second, emanating from a fixed fork; so, 
if a star, which only sends forth those rays which vibrate 
504,750,000,000,000 times a second, should move toward the 
eye with a velocity of 2,442 kilometers, or 1,517 miles, its color 
would change to that given when D, emanates from a stationary 
Soda-flame, 
Art, XXXIV.— On some points in the Geology of the South- 
west; by E. W. Hitearp, of the University of Mississtpp 
THE third annual Report of the Geological Survey of 
Louisiana, by Prof. F. ¥, Sopiina, contains a number of 
statements and discussions controverting, apparently at least, 
Some of the facts and views heretofore published by me, 
especially as regards the quaternary history of the Mississipp1 
Valley and Gulf of Mexico. While some of the points made 
by mty respected friend are based merely upon misunderstand- 
ings, there are others which result from material differences in 
Mi ec ee of facts, and as such require notice at my 
ands, 
As regards the inadmissibility of Prof. Hopkins’s conjecture 
that the Labrador current may have been instrumental in dis- 
tributing the drift over the Mississippi Valley, I have little to 
Say that could add to the cogency of ana’s remarks on 
€ same subject, in the August number of this Journal. 
The southern drift bears everywhere the character of a 
deposit formed by “fresh water in a state of violent flow, 
and devoid, or nearly so, of animal | 2 I dl 
stated, on the strength of an array of evidence against whic 
oF stratigraphical fact. For the origin of 
hold myself responsible; but I must demur 
Am, Jour. pogeéea Sertes, Vou. IV, No. 22—Ocr., i 
1 
