of recovering cosmonauts who landed in inaccessible areas. In the 1960s, Joseph Jean de Bakker was the busy owner of the De Bakker machine factory in Hulst in the southwest of the Netherlands. He was also a keen fisherman, but he did not want his fishing time to be constrained by the vagaries of the tide. His solution was the Amphirol, a screw-propelled vehicle superficially similar to the Marsh Screw Amphibian. The Amphirol was able to convey him over the sticky clay revealed by the outgoing tide and to swim in water at high tide. De Bakker's Amphirol had a top speed of on mud and in water. It was powered by two modified DAF 44/55 variomatic transmission units; this made possible the significant innovation that the flanged cylinders could be deliberately driven in the same direction so that the vehicle could crab sideways on dry land at the alarming speed of . Also, when moving sideways, steering is effected by shifting the front of the cylinders so that they are no longer parallel – giving a large minimum turning radius. Amphirols are used for ground surveying, for grooving the surface of newly drained polders to assist drying, and to carry soil-drilling teams. Today modern vehicles, widely known as amphirols, perform specialised tasks such as compacting tailings from industrial processes. The advantage of these machines to tailings densification is that they provide a means to allow water or process liquor to run off without repulping the profile. This approach subsequently largely negates the impact of rainfall on densification and dewatering. However, the lighter, faster machines are better suited to marginal terrain access, but not densification due to repulping and their limited penetration depth. The process of using these machines specifically for tailings and dredge spoil densification is commonly termed "mud farming" in the mining industry. Recent developments The British Ice Challenger exploration team used a screw drive in their Snowbird 6 vehicle (a modified Bombardier tracked craft) to traverse the ice floes in the Bering Strait. The rotating cylinders allowed Snowbird 6 to move over ice and to propel itself through water, but the screw system was not considered suitable for long distances, and the cylinders could be raised so that the vehicle could also run on conventional caterpillar tracks. The Ice Challenger website says that the design was inspired by a Russian vehicle used to pick up cosmonauts who