ABSTRACT
In Table III appended, mines are classi ed according to the derivation of the major part of their output in cases in which more than one of these methods are employed. e Table shows no notable changes. Another tin dredge commenced operations in Mergui during the year, and in general underground mining increased together with the use of monitors. […]
In hydraulicing, the mineralised ground is broken up and excavated by jets of water under pressure. Water must be impounded by dams or diverted from streams and conducted by ditches or pipes to a tank above the working place. From this tank it is piped down to the working place and the issuing jets of water are controlled and directed by means of monitors. e ore-bearing ground is broken down, not only by the direct impact of the water, but also by under-cutting the banks and causing them to cave by gravity. Where high banks are being undercut in this way, skill and a knowledge of ground must be exercised in order to prevent the occurrence of large landslides that may overwhelm the monitors and the men working in the ditches or de-stoning some distance back from the face. As the water ows away from the face the broken ground is carried with it to the sluice ditches. Boulders and rocks, too heavy to be transported by the ordinary ow of water remain on the bedrock or in the ditches. If the rocks are large they may require sledging or blasting before removal is possible by the de-stoning gang.
