Charles Mackay's "The Scenery and Poetry of the English Lakes: A Summer Ramble" (2nd edition, Longman & Co., 1852) may or may not have been based on personal experience, but apart from calling Lord Muncaster an Earl, it's reasonably accurate about Eskdale, which is described in chapter 8 [following a description of Wasdale]:

While in this neighbourhood, few do, and none should omit, taking the opportunity to pay a visit to Eskdale, or Eshdale, if it were no other reason than to see Birker Force and Stanley Gill. These two waterfalls are often mistaken the one for the other; and the traveller who has seen the first is not always aware that, at the distance of three-quarters of a mile, there is another in every respect as fine, or finer. Birker Force dashes over a bare preciptious rock, and Stanley Gill, somewhat inferior in height, is equal to it in beauty and grandeur. The original name of the latter was Dalegarth Force, which has been changed, out of compliment to Mr. Stanley, of Ponsonby, the proprietor of the estate on which it falls. It is far up a narrow and richly-wooded ravine, and the road not being easily found, it may be as well for the traveller in search of the picturesque to inquire at the farm-house called Dalegarth Hall, where a guide may be obtained. Birker Force is by some considered the finest waterfall in Cumberland. The mopst convenient mode, however, of proceeding into this wild region, is to make an extension of the trip from Ambleside to Coniston, of which an account has already been give; and of which all the stages are duly recorded in the guide-books. At a point in this region called Esk House, pronounced Ash Course, may be seen the whole of Borrowdale and Derwentwater, with Skiddaw in the rear, visible from his base to his cope. The river Esk forms a succession of beautiful falls, for fully five miles of its course.

Burnmoor, with Scaw Fell in the distance and the wild and desolate-looking tarn in the middle, are also points of some attraction to the majority of tourists; but, like Birker Force and the beauties of Eskdale, they are more conveniently seen by the traveller who starts from Coniston.

From Wastdale and Eskdale there is a somewhat circuitous, but very interesting route, by Muncaster Castle, Gosforth, Ponsonby, Newton, Egremont, and Copeland Forest, to Ennerdale Water, Buttermere, and Crummock Water, and so by Newlands back to Keswick. Following the course of the Esk, seawards, we pass MUncaster Castle, on a wood-crowned steep, the ancient seat of the family of the Penningtons, Earls of Muncaster. The country in this neighbourhood, now green and luxuriant with wood, is said to have been bleak and bare before the late Earl undertook its improvement. He covered the hills with trees- now of a goodly growth; introduced various breeds of cattle; irrigated the fields; and increased his own wealth, and the wealth of his dependants, by his judicious expenditure. About a mile and a half to the east of the castle, on the opposite side of the Esk, upon an emienence called Birkby Fell, are ruins of considerable extent, which the country people call the remains of the ancient "city of Barnscar." They extend for about three hundred yards one way, and one hundred the other; and have long puzzled antiquaries to account for them- as there is no historical record in existence which throws the smallest light upon the subject. The small market and sea-port town of Ravenglass is about a mile and a half from Muncaster, at the confluence of two small streams, called the Mite and the Irt; but it is in no respect remarkable. From this place we follow the high road to Whitehaven as far as Gosforth, where the lover of the picturesque will admire the situation and architecture of the church; and where the antiquary will delay his steps for a short time to take a look at a tall cross in the churchyard, supposed to have been erected by the Danes.

[Yes, this is the same illustration as in Sylvan's Guide, 1847]