With regard to the possibility, there can be no doubt, for more than a century ago the Dutch Government constructed a jetty 8000 _met._ in length in the Bay of the Lion, near the Cape, in water more than sixteen _met._ deep, in spite of the continued tempestuous weather which succeeds the settled calms in those latitudes. Such a work, considering the depth of water, must have required a quantity of materials at least four times as great as that required for the two jetties and the mole at Pelusium. It was undertaken by a nation not over rich, at a time when steam was unknown, and before the invention of machinery, which saves so much time, expense and labour. There can be no doubt then, that if the cutting of the Isthmus is admitted to be advantageous, it will be easy to overcome all difficulties. With regard to the method of constructing these works, opinions are no less divided. Some engineers, grounding their opinions on ancient constructions, recommend that the moles should be formed of immense blocks of stone of thirty to forty _cubic metres_. Others are of opinion that the only means of preserving the roads from the accumulation of sand, is to construct the moles and dykes of open masonry. There are also some in favour of walls in hydraulic masonry with vertical facings. But, our own opinion is, that in so important an enterprise, every theoretical hypothesis should be discarded, and that we ought to be guided solely by the experience we have acquired in works of an analogous character already executed. And this is what we have done in adopting the system of loose stones, as it has been carried out with success: 1. For the dyke at Cherbourg which is 3768 _met._ long in a depth of water of 14 _m._, 80; 2. For the jetty at Plymouth which is 1364 _met._ long in a depth of 11 _met._ and more; 3. For the dyke in the Bay of Delaware 1200 _met._ long, with a depth of 14 _met._; 4. For that of the Bay of the Lion 8000 _met._ long, in depths of more than 16 _met._