While the largest size triple-effect vacuum plants are capable of turning out 1,000 tons of salt per diem, with brine at or near saturation, and produce about 6 tons of salt for the combustion of 1 ton of coal, it is a very expensive process to operate as well as to install. The cost of the plant ranges from £26,000 to £100,000, and a large percentage of skilled labour is required in its manipulation. But, despite the high initial cost, and the fact that it only makes one grade of salt, it is extremely complicated, and has to be stopped for 4 hours in each 24 for the purpose of boiling out and cleaning up the pans, the vacuum plant is a highly efficient piece of mechanism, and for a while it remained the best and most economic system on the market. But the Vacuum process was not destined to remain long without a rival. In point of fact, the merits of the American invention had scarcely obtained recognition when a new furnace was designed which, when applied to the open-pan system and subjected to practical tests, proved an entire success. The late James Hodgkinson, the patentee, was not a salt-man, but the head of a Manchester firm of engineers and machinery manufacturers, and it was a professional visit to a salt-works which revealed to him the crudity of the brine-boiling operation and gave him the idea of adapting to the salt furnaces a mechanical stoker of his own invention, which was already being operated for other manufacturing purposes. In the development of his idea, and with his mechanical stoker as its foundation, he perfected the Hodgkinson Patent Salt-Making Process, the advantages of which over all other processes for the manufacture of salt from brine have been summarized by Sir Thomas H. Holland, D.Sc., F.R.S., under the following six heads-- 1. Complete utilization of the heat derived from the fuel employed. 2. The absolute maintenance uniformly of this heat. 3. The fact that finely-divided first-quality table salt can be produced in the dry form fit for dispatch to the market without grinding or other preparation. 4. The fact that coarsely crystallized salt can be produced at the same time as the finest table salt. 5. That the proportion of the different grades of salt can be varied at will, as well as maintained constantly, to suit the varying requirements of the market. 6. The automatic and continuous removal of the salt as fast as it is precipitated from the brine. The essential features of the Hodgkinson plant consist of (_a_) a mechanically-stoked furnace for the production of heat; (_b_) a primary closed evaporating pan, 30 ft. in diameter; (_c_) two secondary circular pans, 25 ft. in diameter; (_d_) four open rectangular pans, 60 ft. by 25 ft.; (_e_) a series of folded steam-jacketed pipes for heating the inflowing brine by the waste steam; and (_f_) a condensing arrangement to produce a partial vacuum in the closed pans.