HAYNES.
William Haynes in 1860 invented a process for separating mineral sulphides from the gangue or rocky constituent of an ore by the use of oily, gummy, or bituminous matter. This was not a flotation process, but must be considered the pioneer movement in that direction, as Haynes recognized the fact, all important in later developments, that oily substances have a greater affinity for sulphides and metals than they have for oxides and earthy substances. No commercial application of this invention is known to have been attempted.

BRADFORD.
Hezekiah Bradford, in 1886, invented a process of concentration based on ' surface tension ' factors, but no commercial application of the idea is known to have resulted. His patent is an important and interesting one, because , the flotation of sulphide particles on the surface of a liquid at rest is clearly set forth.

EVERSON.
Carrie J. Everson, in 1885, invented a process for separating the sulphides in an ore from the gangue. She made use of the selective action of the oil for sulphides, discovered by Haynes, but she also carried the idea two steps further. She discovered (i) that acid, added in small quantity to the pulp, greatly increased the selective action of the oil ; and (2) that the oiled mineral could be separated from the gangue by giving the mass thorough agitation, and allowing the sulphides and the oil to float to the surface, while the gangue escaped at the bottom of the vessel. The amount of oil used is variously stated in certain experiments as 6%, 12%, and 20% ; the amount of acid was less than i%. It is worthy of note that none of the quantities of oil specified are sufficient to effect the flotation of the sulphide contents of the ore by the buoyancy of the oil alone, and the flotation must, therefore, have been effected by some other means. The new principles disclosed in this patent were that acid increases the selective action of the oil, and that minerals can be separated from each other by allowing some to float and others to sink. Miss Everson stumbled across the idea quite accidentally. Some sacks in which concentrate had been shipped to her brother's assay-office at Denver had become greasy, and in the process of washing the sacks, the germ of the idea of oil-flotation came under her observation. Attention should be directed to the fact that this invention is strictly feminine in its origin. No masculine assayer probably ever did or ever will launder sample-sacks or ore-bags ; when they have reached the condition in which they need washing and where simple shaking does not make them available for further use, they are discarded. When she had the greasy concentratesacks in the wash-tub and gave them such agitation as was incident to the operation of washing, it only required the customary acutejness of observation of the Western lady school-teacher to grasp the essential facts of sulphide flotation. This process was tried on a fairly large scale at Baker City, Oregon, in 1889, and also near Denver in the same year. A capitalist by the name of Thomas F. Crilley financed the undertaking. In the process as tried at Baker City, under the name of the Crilley & Everson process, the ore was crushed to 5o-mesh, weighed, and roughly mixed with a thick black oil. Boiling water, containing enough acid to give it a tart taste, was then added to the ore. 2 A thick scum of mineral and oil rose to the surface, and was skimmed off, leaving the gangue at the bottom of the vessel. 4 This process was improved in 1892 by Hebron and Everson, whereby they combined pulverized ore with a buoy-stock in a dry state and then applied the prepared ore to a stratifying apparatus into which aircould be introduced for the purpose of producing effervescence.

The newspaper accounts of the attempts to apply this idea give one a strong impression that if the invention had been a less startling innovation it would probably have received more attention from engineers and metallurgists and the development of the idea would probably in that case have taken place many years before it did. The competition for ores and products was also less keen at this time than later and there was therefore not the incentive there is today to turn refractory ores to account. No further definite commercial advance was made, and nothing more was heard of concentration by flotation until 1894.

ROBSON & CROWDER.
In 1894 Robson & Crowder invented a process for separating sulphides from gangue ; they made use of the idea of oil-selection, but they did not recognize the benefit of acid in increasing this selective action, as Everson had done. Their invention differed from former similar ones in that they used but little water ; they say, 25 to 30%. They mixed the ore and water in a vessel having a suitable agitator, added the oil at the bottom of the vessel during agitation, and allowed it to overflow. Presumably, after a time, the oil had selected and carried over all the sulphides, leaving the gangue, mixed with oil and water, in the bottom of the vessel, from which it could be drawn off. The process was tried at the Glasdir mine in Wales, on a fairly large scale. This mine was the place where Elmore later developed his idea of oil-flotation. In April, 1896, James Brothers made a careful examination of the plant and process for a client, and reported that the process was worthy of development, as it seemed adapted to a large class of ores at that time untreatable by other processes. Nothing material came of this effort, however, and the idea lay dormant until 1898, when F. E. Elmore advanced it apace.

ELMORE (OLD PROCESS).
Francis E. Elmore, in 1898, invented a concentration process that involved the idea of oil selection and the idea of flotation in a freely flowing acid pulp. He mixed the ore with several times its weight of water, and an equal, or several times greater weight of oil in a revolving drum,* so constructed and operated as to give a mixing effect without breaking up or emulsifying the oil, which was added with the ore. He did not mention the amount of oil used, but from the fact that he described in his patent a pump for the oil and a centrifugal apparatus for separating the concentrate from the oil, it is inferred that the amount of oil used was considerable. After thus gently mixing, the mass was allowed to run into a spitzkasten, where the oil carried the sulphides to the surface, and the gangue and the water were removed from the bottom. This invention marks a decided advancement in flotationconcentration, and was put into operation in a workmanlike manner.

The process had commercial application on a large scale. It was in the hands of capable engineers, who were not oblivious to its imperfections, and who appreciated that no one process is ever a cure for all the troubles incidental to the treatment of ores. They tried consistently to adapt the process to suitable ores, and where they made mistakes these were only such as must be made when development along new lines is attempted. This process was the first of the kind to approach commercial success, and it was1 a commercial success in many places ; but further improvements in flotation concentration have rendered the method obsolete.

The process was tried by the Boston Consolidated Co., Cape Copper Co., and Namaqua Copper Co. 1 The United States rights were2 purchased by Charles Butters, who tried it on the ore of the Mammoth Mining Co., Utah.3 Companies were organized in Canada, Great Britain, Sweden, Australia, and plants were built in Norway, England, and in British Columbia on the Le Roi mine. The Le Roi plant had a long series of vicissitudes, and was finally closed down. Plants were built at Tywarnhaile in Cornwall, at the Sygun mine in Wales, 8 and at the St. David's mine in Wales. In 1903, the firms of S. Neumann & Co. and Wernher, Beit & Co. purchased a quarter interest in the rights for the whole world, and prepared to push the development and application of the process. The year 1905 may be said to close the activities of the old Elmore process, as most of the plants were either closed down entirely or modified for what is now known as the Elmore vacuum process.