PART IV.

Form and dimensions of the Retorts originallyemployed for manufacturing Coal Gas .

The proper mode of constructing - the retortsin which the coal is distilled, and the art of ap-plying 1 them form an object of primary importancein every gas-light establishment. According as themanufacture is conducted in these respects with adue regard to physical prii ciples, depends thequantity of gas which can be obtained in any giventime, from any given quantity of coal, the con-sumption of fuel requisite for the production ofthat quantity of gas, the degree of deterioration towhich the distillatory vessel is subjected, the qualityin some measure, of the gas itself; and, as theultimate result of all these circumstances, the cheap-ness at which the gas light can be furnished to the

consumer.