their day. The Clyde was capable of retrieving logs from four different points at the same time. Each cable, or lead, was approximately in length. Once the logs were attached and a clearance signal was sent for retrieval, they could be skidded at a speed of . Working conditions around these machines were very dangerous. The largest of these was the Lidgerwood skidder, which not only brought logs to the landing from the cutting site, but loaded them onto railroad cars as well, making it both a skidder & loader. In New Zealand cables were run five miles. Modern equivalents Contemporary skidders are tracked or four wheel drive tractors with a diesel engine, winch and steel, funnel-shaped guards on the rear to protect their wheels. They have articulated steering and usually a small, adjustable, push-blade on the front. The operator/logger is protected from falling or flying debris (or parted cables, or rolling over) by a steel enclosure. They are one of the few logging machines that is capable of thinning or selective logging in larger timber. Forwarders can haul small short pieces out, but if mature timber is to be thinned, a skidder is one of the few options for taking out some trees while leaving others. While selective logging can be done badly in a host of ways, taking some trees while leaving some may be a preferred alternative to taking all the trees. The skidder can also be used for pulling tree stumps, pushing over small trees, and preliminary grading of a logging path known as a "skid road". A positive thing about the skidder is that while wood is being yarded (pulled), tree particles and seeds are cultivated into the soil. One disadvantage of skidder logging in thinning operations is the damage to remaining trees as branches and trunks are dragged against them, tearing away the protective bark of living trees. Another concern is the deep furrows in the topsoil sometimes made by skidders, especially when using tires with chains, which alter surface runoff patterns and increases the costs of forest rehabilitation and reforestation. Versions Logging arch A device similar to a skip tongue log skidder except that it is made of steel, including the spoked wheels Cable skidders On a cable skidder, the cable is reeled out and attached to a pull of cut timber, then the winch pulls the load toward the skidder. The winch