GRETA, a river of England, in Cumberland. It rises in the mountain cove of Wythburn, and at the western base of Helvellyn enters the lake of Thirlmere or Leathes Water, through which it flows, and whence it emerges under the name of St John's Beck, flowing thence along the narrow but extremely picturesque valley of St John's, which is bounded on the W. by Naddle Fell, and on the E. by Great Dodd, a hill at the extremity of the Helvellyn chain. The lower end of the dale is closed by Saddleback, which rises on the N., with its deep ravines and rocky projections. This beautiful vale is the scene of Scott's poem of the Bridal of Triermain, and at its entrance from Thirlmere rise "the castled rocks," so graphically described by the poet. At the foot of Saddleback, which rears its summit above "the ruined towers of Threlkeld Hall," the stream is joined by the Glenderamaken, and takes thence the name of Greta. In its further course it receives the Glenderaterra, which comes bounding down between the mountains of Saddleback and Skiddaw. Thence the Greta passes under the woody side of Latrigg ("Skiddaw's Cub"), where its scenery is of the finest and most remarkable kind. Little more than a mile from the foot of Skiddaw stands the town of Keswick, on the left bank of this river, in the most beautiful vale. Quitting the town, the Greta falls into the Derwent at the foot of the noble lake of Derwentwater. The bed of the Greta is stony and rocky, but the channel immediately above Keswick has been to a great extent cleared of the immense stones which, by their concussion in high floods, produced the loud noises described in Wordsworth's sonnet on the Greta. Black's Guide to the Lakes; Works of Scott, Wordsworth, and Southey.