DANISH GROYNES
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   3.	Below the visible foreshore the most promising expedient would appear to be that of fascines, but fascines of special design, in view of the extreme conditions.
  The most recent systematic construction of groynes on a large scale is that carried out on the coast of Jutland between Ferring and Agger.1 The physical characteristics of the land in rear of the coast-line along this frontage of about twenty miles greatly resemble the conformation of the coast-line of Suffolk and Norfolk. In both cases the superficial deposits are those left on the melting of the ice after the Glacial epochs. Extensive areas of marshy country and lakes with connecting streams have in each instance thus been dammed back. The principal impounded waters on the Danish side are those of the Limfjord. This is a wide expanse of mere, and the Thybor6n Canal has been cut out as a navigable approach to it. The Limfjord is a valuable fishing area, and had the attenuated coast-line between it and the North Sea been breached, much rich agricultural land would have been converted into swamp and the fisheries destroyed. The sea bed consists of fine sand with a little shingle, and here and there, at a depth varying from 16 to 32 feet, of sandy alluvial clay. The total expenditure incurred by the Danish Government on the defence of this strip of coast up to July, 1913, was ,£666,000. Of this sum about £55,000 was spent on what are termed “preliminary works”. The Danish authorities, not having had previous experience in groyne construction, deposited blocks of concrete, in which the sand-mortar varied in proportion with the aggregate, and in many cases these blocks subsequently disintegrated. Up to 1894 the practice had been to mix the concrete 1:3:6 and even 1:4:8, but after this date the aggregates were mixed 1:2:4, and subsequently 1:2%:The final proportion for the mortar appears to have been a mixture of 37! lb. of cement to the cubic foot of sand. The sand was white quartz sand, nearly all passing a sieve of 774 meshes per square inch, and nearly all retained on 5800 meshes per square inch. A longitudinal dike or embankment in concrete was constructed, and the
    1 " Experiments upon Mortar, and Diatomaceous Earth as Puzzolana, in Sea-water; with special reference to Groynes in Denmark" (A. Poulsen), Proc. Inst. C. E., Vol. CC, pp. 409-20.