830 OLDER MESOZOIC FLORAS OF UNITED STATES. 
to undermine a small outlier or mesa and cause it to sink down intact 
to a lower level: The question, however, requires more detailed inves- 
tigation than I was able to give it. 
Leaving this phenomenon out of the account, therefore, and consid- 
ering the two exposures in which there is no question as to their 
natural position, we may use them as a means of determining whether 
the strata have any dip and to some extent in ascertaining the amount 
and direction of the dip. The topographic map has a 250-foot contour 
interval, which is too large to be employed with any very great accu- 
racy, and an aneroid can hardly be depended upon for measurements 
made six hours apart, as had to be done in this case, but, as nearly as 
I could judge from all sources of information, the Natural Bridge mesa 
seems to be between 50 and 100 feet lower than the southwestern mesa. 
As the distance is about 5 miles, the dip to the northeast is somewhere 
between 5 and 10 feet to the mile. As, however, the strike was not 
accurately determinéd, there is no certainty that this is the true dip of 
the strata, and.more precise observations on a-much larger scale will 
be necessary to settle this question. 
Although there is no longer any question as to the true stratigraph- 
ical position of these profuse vegetable remains, there are many facts 
which stand in the way of the supposition that the trees actually grew 
where we now findthem. Several accounts’ profess that stumps occur 
erect, with their roots in the ground, showing that they grew and were 
buried and petrified on the spot, but I was unable to confirm any such 
observations, and on careful inquiry of residents of the country who 
had minutely examined every part of the area I was unable to learn 
of a single indisputable instance of such an occurrence. The only 
trunk that I saw standing on end was one that was inverted and had 
its roots high in air. In fact, from the nature of the case, as I have 
just shown, there would be no use looking for any such phenomenon in 
any of the principal fossil forests, since they all lie from 100 to 400 feet 
below where they were priginally deposited. It is only in the beds of 
coarse sandstone that hold them, therefore, that the evidence need be 
sought. This I did with the utmost care, but even here I found no 
example of an upright trunk. 
In this, as I was glad to learn after my return on looking the mat- 
ter up, I was only confirming the observations and conclusions of Dr. 
J. 8S. Newberry, made in 1858 and published in 1861.? 
Dr. Newberry’s statement is as follows: 
I examined these specimens with some care to determine, if possible, whether they 
had grown on the spot, as those of Lithodendron Creek are supposed to have done 
by the members of Captain Whipple’s party, or whether they had been transported 
1Méllhausen, loc. cit. Marcou, Bull. Soc. géol. France, 2d series, Vol. XII, 1855, p. 871. Repeated in 
Geology of North America, etc., Zurich, 1858, p. 13. 
2Newberry, in the Ives Report, p. 80. 
