dered with Portland
cement, and resting on a layer of concrete 1 meter thick. The walls are
likewise of brick and cement, of a thickness of 3.30 meters up to the
ground level, and 2.40 meters thick to the height of 3.44 meters above the
surface. Altogether, 2,988,680 kilos. of cement and 5,570,000 bricks were
used in its construction. In fact, from the bottom of tank to top of roof,
it reaches as high as the monument at London Bridge.

[Illustration: FIG. 1.--SECTION OF GASHOLDER AND HOUSE.]

The construction of the tank offered many and serious difficulties. The
bottom of the tank is fully 3 meters below the level of the Danube Canal,
which passes close by, and it was not until twelve large pulsometer pumps
were set up, and worked continually night and day, that it was possible to
reach the necessary depth to allow of the commencement of the foundations
of the boundary wall.

ROOF OF HOUSE.

The wrought iron cupola-shaped roof of the gasholder house was designed by
Herr W. Brenner, and consists of 40 radiating rafters, each weighing about
25 cwt., and joined together by 8 polygonal circles of angle iron (90x90x10
mm.). The highest middle circle is uncovered, and carries a round lantern
(Fig. 1). These radiating rafters consist of flat iron bars 7 mm. thick,
and of a height which diminishes gradually, from one interval to another on
the inside, from 252 to 188 mm. At the outside ends (varying from 80x80x9
mm. in the lowest to 60x60x7 mm. in the last polygon but one) these rafters
are strengthened, at least as far as the five lowest ones are concerned, by
flat irons tightly riveted on. At their respective places of support, the
ends of all the spars are screwed on by means of a washer 250 mm. high and
31 mm. thick, and surmounted by a gutter supported by angle irons. From
every junction between the radial rafters and the polygonal circle,
diagonal bars are made to run to the center of the corresponding interval,
where they meet, and are there firmly held together by means of a tongue
ring. The roof is 64.520 meters wide and 14.628 meters high; and its total
weight is 103.300 kilos. for the ironwork--representing a weight of 31.6
kilos. per square meter of surface. It is proposed to employ for its
covering wooden purlins and tin plates. The whole construction has a light,
pleasing, and yet thoroughly solid appearance.

RAISING THE ROOF.

Herr Brenner, the engineer of the Erdberg Works, gives a description of how