The steam and ammonia gas liberated in the still pass over into a large lead-lined tub or saturator, and bubbles through holes in a lead worm placed round the circumference at the bottom of the vessel. Sulphuric acid is at the same time run into the saturator, and, at a certain temperature, sulphate of ammonia is formed. The sulphate falls into a well, formed in the centre of the bottom of the vessel, in which are placed two steam ejectors, and these blow it out along with some liquor. This mixture is delivered into hutches having perforated bottoms, through which the ammonia liquor drains off, the solid sulphate being left in the hutch. This is now run by an overhead railway to the drying or storage stalls, and from these it is packed up and dispatched to the market. The exhaust steam and waste gases from the saturator are passed into the retorts, and utilized for the formation of ammonia from the shale, while the spent water is pumped to the spent shale bing, and thoroughly filtered before being allowed to escape from the works. For dealing with the weak acid water recovered from the refinery, the Pumpherston plant consists of lead-lined tubs or crackers, into which a quantity of the acid water is run, and saturated with ammonia gas until it is near the salting point, when it gravitates into settling vessels in order to separate any tar carried over with the acid water. The clear liquid is then drawn into the saturator, where it is quickly converted into sulphate and blown out in the manner already described. So up to date is the whole of the system governing the treatment of the shales and the resulting products, that the pumping of water from the mines, the haulage of the shale to the refineries, as well as driving of machinery in the works, is performed by electric power, the exhaust steam from the engines driving the generators, as in the case of the sulphate of ammonia exhaust, being sent to the retorts for use in the production of ammonia. The process of refining the crude oil obtained from the shale into the various products is somewhat complicated and perplexing to those unassociated with the industry on account of the many distillations and treatments which have to be carried out before a good marketable article is produced. The following outline, however, will give a fair idea of the process adopted throughout Scotland.