THE GREAT RAINBOW NATURAL BRIDGE 
yon wall on its downward curve. The 
Opening, augmented by a gorge cut by 
the stream to a depth of 80 feet below 
the level of the supporting bench, meas- 
ures a vertical distance of 267 feet; but 
the total height from stream-bottom to 
the top of the arch is 309 feet, while the 
abutments at their base stand 278 feet 
apart. The causeway, upon which one 
may be lowered from an adjacent cliff, 
but whose sides are too steep to serve 
for a complete passage, is 33 feet wide 
by 42 feet thick at its keystone point; 
and the limbs are not greatly in excess 
of these dimensions. 
A mere recitation of figures must fail 
to convey an adequate idea of the im- 
posing nature of the bridge. It is not 
the size alone, though this far exceeds 
the greatest masonry arches constructed 
by engineering skill; nor is it solely the 
graceful lines or curvature of maximum 
stability, but rather all of these, that com- 
bine to make this the most remarkable 
single arch now known. It would easily 
span, with room to spare, the dome of 
the Capitol at Washington; or, if hung 
over the Flatiron Building of New York, 
its limbs would come within a few feet 
of the ground, though to the west of 
Fifth Avenue on the one hand and to the 
east of Broadway on the other. 
The arch is carved from a buff-colored, 
fine-grained sandstone, brick-red upon its 
surface and stained with vertical streaks 
of a darker shade. Mostly massive, 
though in part oblique-bedded, the rock 
is only moderately firm, and is easily 
crushed beneath the blows of a hammer. 
Geologically it is a part of the Upper La 
Plata sandstone, a formation of great 
thickness, deposited in Jurassic time over 
a large portion of southeast Utah, south- 
west. Colorado, and northeast Arizona. 
The origin of the arch is simple and 
evident. It was caused by the progres- 
sive narrowing of the neck of a meander 
intrenched between high and steep walls, 
until an opening was made through the 
tongue of intervening rock, permitting 
the stream to cut off its meander by flow- 
ing beneath the arch thus formed. The 
hole, once made, has been enlarged and 
given its present shape by the combined 
action of weathering, expansion, and 
contraction due to changes in tempera- 
ture, and the carving effect of wind- 
blown sand, all of which unite to produce 
the rounded rock-forms so characteristic 
of this region. ‘The abandoned arm of 
the meander is present and unmistakable, 
indicating the former course pursued by 
the stream. 
Though doubtless requiring many years 
for its formation, the arch is nevertheless 
a very recent geological feature, and des- 
tined to withstand the forces that gave it 
being for only a brief period as geologic 
time is reckoned. 
The bridge was first visited by white 
men and its existence made definitely 
known on August 14, 1909. It was then 
reached by a party consisting of W. B. 
Douglass, of the United States General 
Land Office, with four assistants; Byron 
Cummings, of the University of Utah, 
with three students; John Wetherill, of 
Oljato, Utah; and two Piute Indians, 
Jim and Nasjabegay. Douglass was act- 
ing under instructions from the Depart- 
ment of the Interior, dated October 20, 
1g08, to investigate a reported natural 
bridge in southeast Utah, with a view to 
making it a national monument if found 
of sufficient interest. An attempt was 
made in December, 1908, to locate the 
bridge, but was abandoned on account of 
snow. The search was renewed in Au- 
gust, 1909, the party being joined at 
Oljato by Cummings, Wetherill, and the 
three students. The arch was surveyed 
by Douglass, and the figures herein used, 
as well as the details of its discovery, 
are taken from his official report to the 
Land Office. 
The bridge was undoubtedly known 
to the Indians prior to its discovery by 
white men; but as to the actual knowl- 
edge of it there is uncertainty. Douglass 
relates that Whitehorsebegay, his guide, 
on a second visit to the bridge, would not 
go beneath the arch, but laboriously clam- 
bered around one side whenever it was 
necessary to pass. Later Mrs. John 
Wetherill, an accomplished Navaho lin- 
guist, ascertained from an old Navaho 
that the arch is supposed to represent 
the rainbow, or sun-path, and one who 
