The ammonia-soda process was first patented on 30 June 1838 by Harrison Gray Dyar and John Hemming, who carried it out on an experimental scale in Whitechapel. Many attempts were soon after made in the same direction, both in England and on the continent of Europe, the most remarkable of which was the ingenious combination of apparatus devised by J. J. T. Schloesing and E. Rolland. But a really economical solution of the problem was first definitely found in 1872 by Ernest Solvay, as the result of investigations begun about ten years previously. The greater portion of all the soda-ash of commerce is now made by Solvay's apparatus, which alone shall be described in this place, although it should be borne in mind that the principles laid down by Dyar and Hemming have been and are still successfully carried out in a number of factories by an entirely different kind of apparatus.