The tank in which the gasholder floats has an internal diameter of 61.57 meters, and therefore a superficial area of 3,000 square meters; and since the coping is 12.31 meters above the floor, it follows that the tank is capable of holding 35,500 cubic meters (7,800,000 gallons) of water.  The bottom consists of brickwork 1.10 meters thick, rendered 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.