327 
AND c;e:m£.te.h.ic 
were made b}' Congress to purchase 2,000 acres, in- 
cluding the Creek, for the establishment of a national 
zoological garden, and, adjoining it on the north, a 
national park, known as Rock Creek Park. While 
the primal beauty of this region has, perhaps, not been 
enhanced by the building of perfect driveways and 
many bridle paths and the construction of handsome 
bridges, these works have made it possible for the 
country lover to visit and see this section, heretofore 
the haunt only of a great variety of birds and wood 
and water animals. 
The earlier history of the District of Columbia bird 
and animal life shows Rock Creek to have been an 
exceptional breeding place. Over 500 species of birds 
have been observed within ten miles of the national 
Capitol building, and 100 have been known to breed 
within this limit. Manv of these have retired from the 
STYLISH LITTLE CEMENT AND PEBBLE BRIDGE. 
Crossing a tributary of Rock Creek in Rock Creek Park. 
scene since the opening of the Park ; but in the early 
mornings of spring. Rock Creek is still alive with 
dozens of species of feathered songsters. 
The city of Washington itself is rapidly encroach- 
ing upon the park ; and while the conservatives vigor- 
ously opposed such a large government expenditure in 
securing this land, the wisdom of Congress is now 
apparent. Magnificent residence structures now over- 
look the park from the city side, while beyond, land 
which a few years ago was undivided farms is now 
being built up with handsome suburban residences, and 
the trolley takes people ctuickly back and forth from 
the city. One of the most important improvements 
is the extension of Massachusetts avenue. This is a 
government project nearing completion, and costing 
about $200,000. The creek flows through a capacious 
granite tunnel with a 50-foot span covered by a huge 
embankment 80 feet high, which rises to the grade of 
the avenue, enabling it to cross the Rock Creek ravine. 
Another large bridge project for which the pier 
foundations are going down is the extension of Con- 
necticut avenue northwest, the cost of which will be 
about three-cj[uarters of a million dollars. This impos- 
ing masonry bridge will be from one of the best de- 
signs of the late George S. Morrison, assisted by Ed- 
ward P. Casey, whose work in bridge architecture has 
attracted considerable notice. The bridge will have 
five full-center spans of 150 feet each,' and two full- 
center end spans of 82 feet each. The piers of the 
large arches are 20 feet thick ; and those between the ' 
large and small arches, 37 feet. The bridge will be , 
52 feet in width between the faces ; and the total length 
between abutments, 1,341 feet — a quarter of a mile. | 
Above the main arches are a number of full-center i 
spandrel arches having spans of 14 feet each, and sup- i 
ported by transverse span- > 
drel walls 3 feet thick. , 
These arches are open over 
the 150-foot spans, but 
closed by face walls at the ! 
piers and over the 82-foot 
arches. ITe main arches 
are to be built of i ;2 :4j4 
Portland cement concrete ; j 
the transverse walls, span- I 
drel arches, and most other f 
parts, of I :2^ :6 Portland | 
cement concrete. 
One of the handsomest 
rustic ornaments of the [ 
Park is a steel, rock, and ' 
cement bridge faced with 1 
rough, natural boulders, 
each as large as the body 
Cost $4,200. of a big man. This struc- 
ture justly has the name of 
being one of the most artistic examples of engineering 
construction in the country. It- has an 8o-foot span 
and a 15-foot rise, and carries a 23-foot roadway. The 
clear width between the parapets is 23 feet ; width over 
all, 27 feet. This locality of Rock Creek made it desir- 
able to build a boulder bridge, if possible, for aesthetic 
reasons; but as only $17,500 was available for con- 
struction, it was necessary to adopt some less expen- 
sive type, that selected being a Melan concrete steel 
arch with a boulder facing, the concrete of the soffit ' 
being artificially darkened to harmonize with the faces i 
of the stones. The specifications state that the boulder l 
face of each stone shall project at least two inches be- j 
yond the neat lines of the bridge and not more than j 
fifteen inches. The mortar consists of one part Port- i 
land cement and two parts sand. Two men were em- il 
ployed to do the entire boulder work, which while ap- | 
parently natural, required dressing of the interior faces. 
i'l 
