pee 
1884. | Recent Literature. 401 
it to another occasion, and meanwhile draw attention to Mr. Gil- 
bert’s elaborate essay on Lake Bonneville, a subject which he has 
studied for a number of years past. 
The sediments of this ancient Quaternary lake rest upon Plio- 
cene rocks, which are hard enough to be used as building stone, 
and in many places have been upturned, faulted, while portions, 
separated from their continuations in the valley, have been carried 
high up on mountain flanks, where they have been eroded into 
typical mountain forms, 
From his study of the lake sediments and ancient beaches, Mr, 
Gilbert suggests the following history of the lake: 
1. A long period of dry climate and low water, during which 
the mountains of the desert were buried and the alluvial slopes 
of marginal mountains were formed (PI. x111). 
2. A period of moist climate and high water, during which the 
yellow clay was deposited and the shore was carried within ninety 
feet of the summit of the lowest barriers of the basin. 
3. A period of extreme dryness, during which the lake disap- 
peared and its salt was buried. 
4. A relatively short moist. period, during which the white 
marl was thrown down, and within which the water overran the 
— , diminishing by erosion its height at the point of dis- 
arge. 
5. The present period of relative dryness. 
‘he volcanic rocks of the lake valley are basalts; of these 
Pavant Butte (PI. xrv), situated between Fillmore and Deseret, 
'sthe most conspicuous. It is entirely composed of tuff. Mid- 
way between its base and its summit it is encircled by a terrace 
ned at the highest stage of the lake. The mountain was a 
acustrine volcano; its cone having been completed during 
the highest stage of the lake. 
hag gate other hand another volcano, the Tabernacle (Pl. xv), 
oF thee volcano began to be formed there during a high stage 
ott below the level of the vent; while facts show that the date 
dene aast eruption from the vent was just before the final subsi- 
then, of the water. The period of volcanic activity has lasted, 
leas through the entire history of the lake, and perhaps the end 
ee been reached. “No one,” says Mr. Gilbert, “ who 
Preece ae fresh, black, unworn surfaces of the most recent 
mes still absolutely barren of vegetation, could be affected by 
cent fires it should some day be announced that the now quies- 
Ein had again broken forth”. o es 
ville 22'S that there is a difference in the height of the Bonne- 
now snd Provo shore lines, nejther of the two shore lines. being 
been or, or parallel; hence it is inferred that there have 
~~ graphic movements both during the existence of the last 
ba Xv. —yo, Iv. 26 
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