Dams forming storage reservoirs, which are intended to impound large volumes of water, must necessarily be built of considerable height, except in a very few instances where favorable sites may exist. Recent discussions would indicate that a new interest has been awakened in the construction of high earth dams. As related to the general subject of storage, it is with the high structure rather than the low that this study has to do. To the extent that “the greater includes the less,” the principles here presented are applicable to works of minor importance. Many persons who should know better place little importance upon the skill required for the construction of earthwork embankments, considering the work to involve no scientific problems. It is far too common belief that any ordinary laborer, who may be able to use skillfully a scraper on a country road, is fitted to superintend the construction of an earth dam. It has been said that the art of constructing earth dams is purely empirical, that exact science furnishes no approved method of determining their internal stresses, and that in regard to their design experience is much more valuable than theory. When the question of stability is fully taken into consideration, it certainly requires a large amount of skill successfully to carry out works of this character. Extreme care in the selection of the site, sound judgment in the choice of materials and assiduity in superintending the work while in progress, are all vitally essential. Classification of Dams. Dams may be classified according to their purpose as diverting dams or weirs and as storage dams. The former may be located upon any portion of a stream where the conditions are favorable, and the water used for manifold purposes, being conveyed by means of canals, flumes, tunnels and pipe-lines to places of intended use. These dams are generally low and may be either of a temporary or permanent character, depending upon the uses to which the water is put. Temporary dams are made of brush, logs, sand bags, gravel and loose rock. The more permanent structures are built of stone and concrete masonry. Storage dams may be classified according to the kind of material entering into their structure, as follows: (1) Earth; (2) Earth and Timber; (3) Earth and Rock-fill; (4) Rock-fill; (5) Masonry; (6) Composite Structures.