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 gir