GASOMETERS. 143 



Tank for the above. 



*. d. 



752f Cubic yards of excavation, at Is. - 37 12 8 



107 Cubic yards of puddling at the bottom of tank, 



at 1*. 6d. 806 



246 Superficial feet of York flagging under wall, at 



Is. 9d. - 21 10 6 



5 Rods of brickwork in mortar, at 12 10*. 6815 



119 Cubic yards of puddling, and filling in behind 



wall, at Is. 6d. - 8 18 6 



30 Cubic feet of Bramley Fall stone for base of tri- 

 pods, at 4*. Bd. 676 



347 Cubic yards of earth carted away, at 2s. 2d. 37 1 10 



188 6 6 



I have given the above estimates of gasometers that have been executed, to 

 serve as some guide to the knowledge of the cost of that part of the apparatus. 

 The prices of the ironwork will vary considerably at different places, and also 

 from different manufacturers. A few months ago I received estimates from 

 two houses for a gasometer fifty feet diameter and eighteen feet deep, to be 

 delivered in London in convenient sheets for shipment ; one price was 250, 

 the other 176. It is requisite, therefore, before deciding, to examine into 

 the merits of the contractors as workmen, and also to determine the precise 

 meaning of their tenders. 



It is hardly necessary to observe, that the cost of brick-tanks will never be 

 twice alike. If the ground in which the tank of the gasometer represented in 

 the engraving was built, had been less favourable, the thickness of the retain- 

 ing wall must have been greatly increased, and other expenses incurred, per- 

 haps amounting to one half more than the estimate given here. 



The estimates for the tanks of the two last gasometers will seldom be ex- 

 ceeded, as they were built in ground requiring strong rivetments. 



If the ground in which the tank has to be built is examined by a practical 

 man, the cost can be estimated to within almost a few shillings. 



The " working pressure " of a gasometer will depend upon the area of water- 

 surface, and the weight of the vessel itself. For example, in the gasometer 

 quoted as 100 feet diameter, the area of water- surf ace is 7854 feet, a stratum 

 of which 5^jths deep, will be equal in weight to the gasometer, viz. 100 tons 



