Like a good general, the ice harvester takes note of the physical advantages of his position. If he can so lay out the field that the current and prevailing winds are in his favor and assist to float the ice toward the house, his strategy is not without reward. Room for refuse ice is needed where it will not impede the ice floating toward the house. The lay of the shore line must not be overlooked, on streams where the current is strong, in calculating for support for the shore ice. The best ice in the field will always be secured as a prime consideration. Quality should always be of the first importance, and, in these days of close competition, pure ice is necessary for success in the ice business. Ice, for any purpose, should never be cut from impure or contaminated water. Too much care can not be given to securing clean, pure, healthful ice for all uses, directly or remotely allied to preserving or curing food products. Natural ice from pure crystal water is one of nature’s purest productions. Having gone over the field and determined the plan of operation, the first task is to lay out the base lines from which the marking and plowing are gauged. Stakes are planted at either end of the line, and a heavy cord drawn taut between them. The hand plow is now passed alongside the line, making a score in the ice from end to end. Sometimes a long board with sights is used for laying out the first line, and a line marker is a cheap substitute for the hand plow. The teeth of the horse marker are now set in the hand plow groove; the guide is unlatched and runs along on top of the ice. Care is taken to keep the marker upright, by firmly supporting the handles. This cuts a groove three inches deep. The blade of the guide is now placed in this groove, and the marker cuts a new groove parallel with the first one. [Illustration: FIG. 12. HAND PLOW.] [Illustration: FIG. 13. PLOW ROPE.] [Illustration: FIG. 14. LINE MARKER.] This operation is continued until the field is grooved in parallel lines over its surface in one direction. Plows are now started in the marker grooves, and are run back and forth until the grooves have been cut about two-thirds through the ice, care being taken to leave not less than four inches of solid ice below the bottom of the groove. Meanwhile the marker is at work scoring the field in lines at right angles to those first laid out. A large wooden square with legs about fifteen feet long is used to square from, and the field is marked and plowed in both directions. When the snow ice plane is to be used, the field is marked out in one direction only. The depth cut is regulated by a planer gauge, attached to the marker, to the thickness of the snow ice to be removed. The runners of the plane set in the grooves and are guided by them.