again washed and thoroughly purified from foreign gases which may have escaped the action of the lime machine; Y, is a waste pipe, the lower extremity of which is sealed by being immersed in water,--it serves to carry away the water delivered by the pipe V, as it has been acted on by the gas. The summary action of this gas apparatus is, therefore, as follows: The liquid products obtained from the coal during the distillation are first deposited in the main condenser L, by means of the pipe K, and from whence they cannot escape until a quantity of tar has accumulated in it to a certain height, and by this means, one of the extremities of the pipes K, K, becomes immersed and hermetically sealed by the liquid which the condenser L, contains. The liquid products, after having accumulated to a certain height in the condenser, overflow the perpendicular portion which it contains, and discharge themselves into the pipe M, from whence they are transported into the tar cistern, fig. 3, by means of the system of pipes N, N, O, whilst the gazeous products are made to pass by means of the branch pipe P, into the lime machine, fig. 2. From this part of the apparatus the gas passes through the pipe T, T, T, into the additional or smaller washing apparatus placed upon a tressel in the cistern of the gasometer, where it is again exposed a second time to the action of a current of fresh water; and from this vessel the gas ascends into the gasometer. The gasometer is furnished with a pipe A, closed at the top, and fixed in one corner of the gasometer, but open at the bottom; it includes another pipe marked B, which communicates with the main pipe leading to the burners, or place where the gas is wanted. The pipe A, which slides over the pipe B, is perforated at the top, the gas passes through these perforations and is thus made to enter into the pipe B, and disposed of as mentioned. C, C, is a tube of safety adapted to the gasometer; its lower extremity remains sealed by the water in the cistern so long as the gasometer is not overcharged with gas; but, if more gas should be made to enter the gasometer than it is destined to receive, this pipe then delivers the gas into the funnel-shaped tube D, which reaches through the roof of the gasometer house, and thus the superfluous quantity of gas is conveyed away into the open air. [41] The condenser in this apparatus is placed at right angles to the row, or rows of retorts. It is furnished at one extremity with a partition placed perpendicularly, and of a height equal to about one-half of the diameter of the condenser. The object of this partition is to prevent the tar, &c. deposited in it, to seal the pipes K, K, and not to discharge itself into the pipe M, till this has been effected. The partition is seen in the drawing.