GAS, COAL 



589 



gasholder itself, this may bo regulated by the main valve, or by water valves of 

 various kinds. Or, as is now usually done, a governor may be introduced between the 

 great gasholder and the main pipe of distribution. With a diameter of 61 feet in 

 the gasholder, the pressure in the highest and lowest positions is the same. 



The gasholders employed in storing up gas until required for use, occupy, upon the 

 old plan, much space, and are attended with considerable expense in erecting. The 

 water-tank, whether sunk in the ground or raised, must be of equal dimensions with 

 the gasholder, both in breadth and depth. The improved construction which we are 

 about to describe, affords a means of reducing the depth of the tank, dispensing with 

 the bridge of suspension, and of increasing at pleasure the capacity of the gasholder, 

 upon a given base, thus rendering a small apparatus capable, if required, of holding a 

 large quantity of gas, the first cost of which will be considerably less than even a 

 small gasholder constructed upon the ordinary plan. 



Mr. Tait, of Mile-End Eoad, the inventor, has, we believe, been for some years 

 connected with gas-establishments, and is therefore fully aware of the practical 

 defects or advantages of the different con- 

 structions of gasholders now in use. Fig. 

 1049 is a section of Mr. Tait's improved 

 contrivance: a a is the tank, occupied with 

 water ; b b two iron columns with pulley 

 wheels on the top ; cc chains attached to a 

 ring of iron, dd, extending round the gas- 

 holder, which chains pass over the pulley 

 wheels, and are loaded at their extremities, 

 for the purpose of balancing the weight of 

 the materials of which the gasholder is com- 



The gasholder is formed by two or three 

 cylinders, sliding one within the other, like 

 the tubes of a telescope; eeeis the first or 

 outer cylinder, closed at the top, and having 

 the ring of iron, d, passing round it, by 

 which the whole is suspended ; // is the 

 second cylinder, sliding freely within the 

 first, and there may be a third and fourth 

 within these, if necessary. 



When there is no gas in the apparatus, all the cylinders are slidden down, and 

 remain, one within the other, immersed in the tank of water ; but when the gas rises, 

 through the water pressing against the top of the gasholder, its buoyancy causes the 

 cylinder e to ascend. Bound the lower edge of this cylinder a groove is formed by 

 the turning-in of the plate of iron, and, as it rises, the edge takes hold of the top rim 

 of the cylinder /, which is overlapped for that purpose. The groove at the bottom of 

 the cylinder fills itself with water as it ascends, and, by the rim of the second cylinder 

 falling into it, an air-tight hydraulic joint is produced. 



Thus several cylinders may be adapted to act in a small tank of water, by sliding 

 one within the other, with lapped edges forming hydraulic joints, and, by supporting 

 the apparatus in the way shown, the centre of gravity will always be below the points 

 of suspension. A gasholder upon this plan may be made of any diameter, as there 

 will be no need of frame-work or a bridge to support it ; and the increasing weight of 

 the apparatus, as the cylinders are raised one after the other, may be counterpoised 

 by loading the ends of the chain c c. 



Fig. 1050 is an elevation of a double or telescopic gasholder of a modern and ap- 

 proved form, with part of a tank. 



The water in the gasholder need not be renewed ; but merely so much of it as 

 evaporates or leaks out is to be replaced. Indeed the surface of the water in the 

 cistern gets covered with a stratum of coal-oil, a few inches deep, which prevents its 

 evaporation, and allows the gas to be saturated with this volatile substance, so as to 

 increase its illuminating power. 



The gasholder may be separated from the purifier by an intermediate vessel, such 

 as is represented by fig. 1051, with which the two gas-pipes are connected. A is the 

 cylindrical vessel of cast iron, a, the end of the gas-pipe which comes from the 

 purifier, immersed a few inches deep into the liquid with which the vessel is about 

 two-thirds filled ; b is the gas-pipe which leads into the gasholder, c is a perpendicular 

 tube, placed over the bottom of the vessel, and reaching to within one-third of the 

 top, through which the liquid is introduced into the vessel, and through which it 

 escapes when it overflows the level d. In this tube the liquid stands towards the 

 inner level higher, in proportion to the pressure of the gas in the gasholder. The 



