del ta

[The name of the fourth Greek letter, corresponding with the English d. As a capital it is formed in the shape of an equilateral triangle. Originally applied to the triangle-shaped island formed by deposits between the two mouths of the Nile; afterward applied to other similarly shaped tracts formed at the mouths of large rivers by two or more diverging branches. The deltas of many rivers, as the Ganges, Niger, Mi i ippi, ., are geologically most instructive, exhibiting, as they do, perfect analogues of many of the older formations in magnitude, variety of composition, alternation of beds, and entombment of plants and animals.