Scientific American Supplement, No. 484, April 11, 1885

Scientific American Supplement,
No. 484, April 11, 1885

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Title: Scientific American Supplement, No. 484, April 11, 1885
Author: Various
Release Date: November 3, 2004 [EBook #13939]
Language: English
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[Illustration]

SCIENTIFIC AMERICAN SUPPLEMENT NO. 484

NEW YORK, APRIL 11, 1885
Scientific American Supplement. Vol. XIX, No. 484.

Scientific American established 1845
Scientific American Supplement, $5 a year.
Scientific American and Supplement, $7 a year.
* * * * *

TABLE OF CONTENTS.
I. ENGINEERING AND MECHANICS.--Bridge over the Blaauw
Krantz Ravine, Cape Colony.--2 engravings.
Torpedo Ships.
The Gas Engine.--By DUGALD CLERK.--Combustion engines.--First
cylinder and piston engine.--Watt's experiments.--First gas
engine.--Principles of the gas engine.
Rapid Construction of the Canadian Pacific Railway.--By E.T.
ABBOTT.
The Osgood Mammoth Excavator.--3 figures.
Capstan Navigation on the Volga.--4 figures.
Steamboat Equipment of War Vessels.--With engraving of winch for
raising and lowering torpedo boats.
Improved Steam Trap.--1 engraving.
II. TECHNOLOGY.--Critical Methods of Detecting Errors in Plane
Surfaces.--By JOHN A. BRASHEAR.--11 figures.
Photometric Standards.--9 figures.
Bleaching or Dyeing Yarns and Goods in Vacuo.--1 figure.
On the Moulding of Porcelain.--By CHAS. LAUTH.--Moulding by
pressure of the air.--Moulding by vacuum.--Drying the moulded
pieces.--2 figures.
Photo-Tricycle Apparatus.--1 figure.
A Photo Printing Light.--1 figure.
A New Actinometer.
Astronomical Photography.
Electricity as a Preventive of Scale in Boilers.
III. DECORATIVE ART.--Alphabet designed by Godfrey Sykes.--An
engraving.
Old Wrought Iron Gate.--An engraving.
IV. GEOLOGY.--The Organization and Plan of the United States
Geological Survey.--By J.W. POWELL.--A topographic map of the
United States.--Paleontology.--Chemistry.--Physical

researches.--Statistics.--Library.--Publications.--General
geology.--Economic geology.--Relation of the general survey to the
State survey.
V. BOTANY, ETC.--The Sunflowers.--Annuals, perennials, etc.--11
engravings.
Lye's Fuchsias.--1 engraving.
VI. HYGIENE, ETC.--Brief Sanitary Matters in Connection with
Isolated Country Houses.--By E.W. BOWDITCH.
Sanitary Cooking.--By V.L. OPPENHEIMER.
Time required to digest Different Foods.
* * * * *

THE BLAAUW KRANTZ VIADUCT IN CAPE COLONY.
This viaduct is built over a rocky ravine on the railway from Port
Alfred to Grahamstown, at a height of about 200 ft. from the bottom.
Its length is 480 ft. 6 in., and the width of the platform is 15 ft., the
gauge of the railway being 3 ft. 6 in. The central span of the viaduct is
an arch of 220 ft. span between abutments, and about 90 ft. height; the
remainder of the space on each side is divided into two spans by an iron
pier at a distance of 68 ft. from the retaining wall. These piers are 36 ft.
2 in. high, and carry girders 144 ft. long, balanced each on a pivot in
the center. One end of these girders is secured to the retaining walls by
means of horizontal and vertical anchorages, while the other end rests
in a sliding bearing on the top flange of the arch.
[Illustration: BRIDGE OVER THE BLAAUW KRANTZ RAVINE,
CAPE COLONY.]
[Illustration: BRIDGE OVER THE BLAAUW KRANTZ RAVINE,
CAPE COLONY.]
In designing the structure the following points had to be considered: (1)
That, on account of the great height above the ground, and on account
of the high price of timber at the site, the structure could be easily
erected without the use of scaffolding supporting it as a whole. (2) That,
on account of the high freights to Port Alfred, the quantity of iron in the
structure should be as small as possible. (3) That the single parts of the
principal span should be easy to lift, and that there should be as few of
them as possible. For this latter reason most of them were made in
lengths of 20 ft. and more. The question of economy of material

presented itself as a comparison between a few standard types, viz., the
girder bridge of small independent spans; the cantilever bridge, or the
continuous girder bridge in three large spans; the single girder bridge
with one large span and several small spans; and the arch with small
girder spans on each side. The suspension bridge was left out of
question as inadmissible. A girder bridge with small independent spans
on rocker piers would probably have been the most economical, even
taking into account the great height of the piers near the middle of the
ravine, but there would have been some difficulty in holding those piers
in position until they could be secured to the girders at the top; and,
moreover, such a structure would have been strikingly out of harmony
with