Rennie has therefore formed the face of the west wall seawards, into two concave curves, These undulate a passing torrent, break its force, throw it off, and mitigate its injury exceedingly. Moreover this pair of concave curves, is but a continuation of angular ground from Tom Herd's Rock, on which the commencement of the wall nearly rests. By adopting a form so simple and yet efficacious, south-west torrents are broken and the wall strengthened in the meantime. Hence at a future day, when ignorance has been hushed, and bile gone to rest, Sir John Rennie is sure to retain an engineering reputation of the highest order. Nor ought a lesson so valuable in the construction of harbours to remain unobserved by the engineering world.

Perhaps, however, the powerful backwater stream of the river Derwent, affords more certain means of constructing a harbour of refuge at Workington, than on any other point within the limits of the Solway Frith. Were a bold projecting breakwater rightly placed to the southwards of the embouchure of the Derwent, operating similarly to Saint Bees Head on Whitehaven Bay, the flowing tide-wave dropping on a line of incidence upon the entrance of Workington harbour, would be sure to render that admirably sheltered port either accessible to vessels of considerable burthen, or nearly so, at all times of the tide. The more especially, when the results produced sug

gested additional works at the immediate entrance of the harbour. As regards a well known travelling beach on the north of the harbour, it would fly before the battery here proposed like chaff before the winds of heaven. The rebounding tide-wave would be sure to fall thereon, and sweep it off; finally producing a bight and scour from both the flowing and ebbing tide.

Maryport harbour might have been similarly constructed, had not art spoiled what tidal laws had presented on the embouchure of the river Ellen; or to apply the emphatic words of a near observer, "God Almighty (in a high tide) had done more good in an hour, by pulling down what had been put up in twenty years, than all their harbour projectors put together." But experience has been disregarded; and those very works have been carried out still more effectively a few years back. Consequently, a breakwater, for which high merit is claimed, is built much too near the harbour and embouchure of the river Ellen, which, similar to the incidents in the brook behind Grun Point, has a strong tendency to silt it up and bar the river channel; while in south-west gales vessels are apt to be driven past the harbour, and stranded on an angle of incidence about 650 yards to the northwards thereof. The scour of the flowing tide passes the harbour altogether, and falls upon a tanyard with all its fury. There the embouchure of the river Ellen and the harbour ought to have

been. But death and destruction lie upon the spot. Previous to any works being erected in defence of the harbour, a plot of green ground intervened between this tan-yard and the beach, showing that the breakwater ought to have been placed on the line of incidence southwards, so as to have brought a scour on the embouchure of the river, and thereby carried vessels into the harbour.

As a subject of science we certainly dismiss the construction of harbours hastily. The tidal laws described in these pages, we trust, however, may lead to a more extensive range of enquiry, verified by experience and illustrated by examples. We certainly feel that we have probed the fountain where true knowledge on this head lies. Providence may be pronounced a universal Engineer, that has left no principle in the construction of harbours un-illustrated, nor any modifications in detail without complete examples to go by. It is true that these require a nice discrimination in practice, accurate observation, great ability, and much experience or communion with physical laws. An ardent hope is at the same time held forth, that a species of knowledge which has become so essential to the marine safety of British life and property, and the unslackened success of our industrial energies, may speedily gain that national attention which the subject so imperatively demands. In truth, to handle these matters as

they deserve, we must seek for a body of facts yet ungathered; means of obtaining them must be resorted to, mature consideration and reconsideration must be honestly bestowed upon them, and in this laborious way we must continue to unroll the hidden papyrus of tidal laws.

In the construction of harbours, an amendment in the channels of navigation on our coasts, and in the reclaiming of land from the sea, an eastwards motion of the earth, a westwards tendency of oceanic currents, and a usual accumulation of drift on the terminus of any tide-wave, would seem to claim intense examination for our guidance in future. Next in consideration to these first premises may be viewed the local configuration of any shore in reference to oceanic currents and inland backwater. By such means gaining an acquaintance with incidents which concern some of our best interests as an industrious and happy people.

CHAPTER VI.

ON THE APPLICATION OF GEOLOGY TO THE LAYING OUT OF RAILWAYS IN ENGLAND, SCOTLAND, AND IRELAND.

IN the application of Geology to the laying out of Railways in the United Kingdoms of Great Britain and Ireland, as population may in some measure be considered a basis of traffic, and a criterion of the extent of inter-communication, we shall assume that an adequate return of profits, and the propriety of adopting the highest facilities of commercial intercourse, mainly depend upon the several masses of population which are found within the range of given termini. We shall accordingly proceed in the classification of England, Wales, and Scotland, into commercial sections, communicating with each other and Ireland also, with a view of framing just outlines of an extended scheme of railway ramifications, suited to the configuration and surface of the United Kingdoms. According to the census of 1831, Scotland had a population of 2,365,000 persons. On this basis, we shall assume that the existing traffic which obtains in our island between any two masses of population to this extent, admitting the ground to be tolerably favourable, may return an adequate