The Baltimore County union. [volume] (Towsontown, Md.) 1865-1909, 1884-08-23
Correspondence Baltimore County Union.
THE B. 81 o. R. R. BRIDGES.

Messrs. Longnecker Bros.:-The preparations
for erection of the sub structure, all under the
trestle and bridge work of the viaducts over the
Great and Little Gunpowder Falls, which were
commenced during the last part of 1883 and re-
linquished temporarily early in the present year
on account of the severity and unsettled state of
the weather, were resumed in April last, and the
manufacture of artificial stone of which the abut-
ments, piers and pedestals are to be composed,
has been in active progress since The of
artificial stone in railroad bridge construction is
q novel feature, and these two bridges, when COM
peted will stand alone of their kind in this or any
other country. This immediate section of the
county is destitute of good building stone, having
regular cleavage, and the destruction of naviga-
ton by immense deposits of silt, the accumulation
of hundred years, at the mouths of the above
streams, renders delivery of natural stone from q
distance to the head of tide, the points where the
Baltimore and Ohio Railroad crosses, very expen-
sive. These facts, no doubt, in q measure deter
mined the B. & o. engineers to artificial stone,
and they contracted last November with the
Hopes Stone Construction Company of Baltimore
county for the stone work of both bridges. How
many of your readers aware of the existence
of this company in their midst, or of the extent
and variety of its manufactures, which consist of
goods of all shapes into which natural stone can
be fashioned?
Artificial stone is not a name significant or in
dcative of durability, quality most essential for
mineral building material where permanency is
the object, and especially is Inability desirable
in material to be used foundation for a rail
road bridge. Experience has taught and expert
ment has demonstrated, however, that concrete,
the beton agglomere of the French, is as dur
able as the best natural stone and capable of
resisting a crushing force, more than sufficient
for all the necessities of architecture. In Africa
and Asia the knowledge and employment of facti-
tious stone antedates the Christian era, and such
stone was much used by the Romans for sea walls,
roads and aqueducts. The use of beton in France
at present seems to be more general than else
where, although its gradual advance in the archi-
lecture of all civilized countries is very percepti
BILE. The thirty seven miles of the Vannes aque-
ducts for supplying water to Paris is of beton az
0ion,ere. the pillars. arches and pipe being one
solid mass of masonry, without seam or joint
Near Paris also is church built in Gothic style
of beton with spire 1856 feet high. 1t is consid-
cred the advanced engineering intelligence of the
day has reached more accurate knowledge of con-
crete preparations than obtained during the Roman
concrete constructive period, whose excellence is
attested by existing works.
The matrix of the beton used on the Gunpowder
is composed both of artificial and natural cements
dampened, which together with clean river sand
dampened and crushed trap rock are all the essen
tial elements employed; though a quickly "set
ting" material in liquid form is introduced, the
patent of DR.. Hopes, who also controls patent
stone desired. In the bridges alluded to above
the concrete will be allowed to retain its natural
color, pleasing grey. The mechanism employed
in manufacture is quite simple. An archimedean
screw, revolving in slightly inclined wooden
trough, thoroughly mixes the sand, cement and
liquid silcate into paste. The sand and cement
introduced in proportionate parts into the
trough with shovels, and the slicate from ee-
waited barrel with spigot, the combination issuing
at the trough's lowest point and falling into a
hollow square chamber of boiler-i iron through an
opening left for the purpose and into which fits
tightly an iron door with appropriate fastenings.
This is called an "incorporator," and is intended
to hold one "working," or dump car load, with
ample vacancy for its free play. This incorpora-
tor is hung upon stout frame by trunnions
placed on obique corners and revolving in jour
mails. To the sand and cement, placed as above,
is then added broken trap rock, reduced to various
sizes, say from four to two inches in diameter, by
q Gates stone crusher, which is driven by
16horse power Page engine, which also revolves
tho screw and incorporation. few revolutions of
the chamber containing the united material and
an everlasting combination is formed. The opened
door releases it into dump cars placed underneath,
from whence it is conveyed rail to its final
resting place. There the application of iron
stamps or hammers in the hands of men gives the
shape of the moulds. Packing the paste in this
way is no unimportant part of the manufacture.
The crusher employed is an advance upon earlier
patents and Styles breaking the heaviest trap
rock with the greatest ease as fast as two men can
feed the hopper, and with no more noise than
would be made in operating ordinary corn
shelter The Commissioners of Hartford have
shown their enterprise by the purchase of Gates
crusher for the reduction of rock lying so plentiful
over their county, with view to its economical
application to their roads.
The Little Falls bridge which is composed of
sixty pedestal shaped columns ranged in sets of
three over the low lands bordering the falls each
set being thirty feet apart, two parallelogram
shaped piers on either side of the stream proper
at distance from each other of 135 feet, and two
abutments at either end that the Baltimore
county side rising from the marsh solid mass
29x14 feet and 40 feet high. The entire structure
will be in extent S65 feet and will be ready for the
superstructure this week and turned over to the
B. & 0. engineers for that purpose by the Hopes
Co.'s engineer, W. f. Goodhue, and his able as
sistants, James r. Carroll and Samuel W. Hopes.
These gentlemen will then turn their undivided
attention to the completion of the two huge abut-
ments on the Great Falls, which will be the only
support of the bridge at that point. These abut
ments will each, when finished, present the form
of double arch of the following dimensions
30x71 feet and 60 feet high.
The Hopes Co. intend to push this work rapid
ly to conclusion, calling to their aid all the i'm
proved machinery that can be applied, including
electric lights. Here in addition to the machinery
on the Little Falls the incorporated material is
conveyed to the west abutment by steam on an
iron cable capable of sustaining strain of twenty
tons, suspended in air some eighty or ninety feet
above tide. The span here will be $50 feet and
calls for an iron truss bridge. The foundations
of both bridges where they approach the banks of
the streams were from necessity sunk fifteen or
more feet below tide.