being allowed to project out about eighteen inches, so that they can receive a wicker-work formed by interlacing them with twigs, the spaces between this wicker-work being filled with broken stone; this forms a very durable and strong facing, which resists not only the action of the current, but, by its elasticity, the shocks of the heaviest waves.

The foot of the exterior slope requires peculiar care for its protection; the shore, for this purpose, is in some places covered with a thick apron of brush and gravel in alternate layers, to a distance of one hundred yards into the water from the foot of the slope.

On some parts of the coast of France, where it has been found necessary to protect it from encroachments of the sea, a cross section has been given to the dikes towards the sea, of the same form as the one which the shore naturally takes from the action of the waves. The dikes in other respects are constructed and faced after the manner which has been so long in practice in Holland.

868. Groins. Constructions, termed groins, are used whenever it becomes necessary to check the effect of the current along the shore, and cause deposites to be formed. These are artificial ridges which rise a few feet only above the surface of the beach, and are built out in a direction either perpendicular to that of the shore, or oblique to it. They are constructed either of clay, which is well rammed and protected on the surface by a facing of fascines or stones; or of layers of fascines; or of one or two rows of short piles driven in juxtaposition; or any other means that the locality may furnish may be resorted to; the object being to interpose an obstacle, which, breaking the force of the current, will occasion a deposite near it, and thus gradually cause the shore to gain upon the sea.

869. Sea-walls. When the sea encroaches upon the land, forming a steep bluff, the face of which is gradually worn away, a wall of masonry is the only means that will afford a permanent protection against this action of the waves. Walls made for this object are termed sea-walls. The face of a seawall should be constructed of the most durable stone in large blocks. The backing may be of rubble or of beton. The whole work should be laid with hydraulic mortar.

22*

END.

JOHN WILEY & SON'S

LIST OF PUBLICATIONS,

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Under the Mercantile Library and Trade Salerooms.

DOWNING.

AGRICULTURE.

FRUITS AND FRUIT-TREES OF AMERICA; or the
Culture, Propagation, and Management in the Garden and
Orchard, of Fruit-trees generally, with descriptions of al. the
finest varieties of Fruit, Native and Foreign, cultivated in this
country. By A. J. Downing. Second revision and correction,
with large additions. By Chas. Downing. 1 vol. 8vo, over
1100 pages, with several hundred outline engravings.
with Supplement for 1872......

Price, .$5.00

With $2.50

"As a work of reference it has no equal in this country, and deserves a place in
the Library of every Pomologist in America."-Marshall P. Wilder.
ENCYCLOPEDIA CF FRUITS; or, Fruits and Fruit-
Trees of America. Part 1.-APPLES. With an Appendix
containing many new varieties, and brought down to 1872.
By Chas. Downing. With numerous outline engravings. 8vo,
full cloth....
.$2.50
ENCYCLOPEDIA OF FRUITS; or, Fruits and Fruit-
Trees of America. Part 2.-CHERRIES, GRAPES, PEACHES,
PEARS, &C. With an Appendix containing many new varie-
ties, and brought down to 1872. By Chas. Downing.
numerous outline engravings. 8vo, full cloth....
FRUITS AND FRUIT-TREES OF AMERICA. By A. J.
Downing. First revised edition. By Chas. Downing. 12mo,
cloth.......
.$2.00
SELECTED FRUITS. From Downing's Fruits and Fruit-
Trees of America. With some new varieties, including their
Culture, Propagation, and Management in the Garden and
Orchard, with a Guide to the selection of Fruits, with refer-
ence to the Time of Ripening. By Chas. Downing. Illus-
trated with upwards of four hundred outlines of Apples,
Cherries, Grapes, Plums, Pears, &c. 1 vol., 12mo....$2 50
LOUDON'S GARDENING FOR LADIES, AND COM-
PANION TO THE FLOWER-GARDEN. Second
American from third London edition. Edited by A. J.
Downing. 1 vol., 12mo...
.$2.00

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DOWNING & THE THEORY OF HORTICULTURE, By J. Lindley. LINDLEY. With additions by A. J. Downing. 12mo, cloth..... COTTAGE RESIDENCES. A Series of Designs for Rural Cottages and Cottage Villas, with Garden Grounds. By A. J. Downing. Containing a revised List of Trees, Shrubs, and Plants, and the most recent and best selected Fruit, with some account of the newei soyle of Gardens. By Henry Winthrop Sargent and Charles Downing. With many new designs in Rural Architecture. By George E Harney, Architect. 1 vol. 4to....

.86 00