microfossil examination as part of a check on how the results of the old surveys compared with the new. Except for some variations relating to the extent of the cretaceous outcrop in the middle of the Channel, the findings tallied nicely. The new Study Group had a number of other elaborate surveys made, too, on the economic and engineering problems involved in the creation and operation of a Channel tunnel or an equivalent means of cross-Channel transport. Besides developing plans for a bored tunnel—the projected double-rail tunnel, interconnected at intervals by cross-passages, is essentially a modern version of William Low's plan of the 1860s, with an extra small service tunnel being added between the main tunnels—the Study Group's engineering consultants developed in detail schemes for a Channel bridge, an immersed railway tube, an immersed road tube, a combined immersed tube with two railway tracks, and a four-way road system on two levels. The bridge proposed would be an enormous affair with approximately 142 piers and with four main spans in the center of the Strait each 984 feet long. These spans would tower a maximum of 262-1/2 feet above sea level to allow the largest ships in the world to pass underneath with plenty of room to spare. The bridge would take no longer to build than a road tunnel, but it would cost about twice as much, and in addition it would be expensive and difficult to maintain and would present a hazard to navigation. The immersed tube proposed for either rail or road traffic (but not both) probably would cost about the same as a bored tunnel and might be constructed in four years. A combined road-rail tube would take about the same time to build, but would be more expensive even than a bridge. Among the best-known schemes for a combined tube is that of a Frenchman, André Basdevant, who has proposed one with a four-lane highway and a two-track rail line. This scheme would pretty much run along the old Cap Gris-Nez-Folkestone route of Thomé de Gamond, and it would even have, like most of Thomé de Gamond's schemes, an artificial island in mid-channel on the Varne. As for the latest scheme for a laid, rather than a bored, tube, it would be no different from Thomé de Gamond's plan in 1834 for a submerged tube, and as in that old plan a trench would be dug, by operations conducted at the surface, across the Channel bottom to receive the tube, which would be prefabricated in sections and towed out to sea to be laid down in the trench a section at a time. This time the digging of the trench would be carried out from a huge above-surface working platform, something like an aircraft-carrier deck on sets of two-hundred-foot-high stilts, that would jack itself up and move on across the Channel as the work progressed. From these and other surveys, the Study Group concluded by March 1960 that the best means of linking Britain and France would be by a rail tunnel, either bored or immersed, which, while avoiding