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.
Channels and Canals.—The marking and plowing being well under way, the channels and canals require attention. Where the current is gentle, and on ponds and lakes, the opening of the channel and canals is not attended with much difficulty. Where the current is swift, as on the large rivers, practical skill is required in opening up the field. The pressure of the current makes it difficult to open the channel and canals, and the shore ice is in danger of giving way. Stays and braces are sometimes employed to anchor the shore ice, and to prevent the channels from closing.
In some instances it has been found advisable to have the channel permanently fixed by piles driven into the bottom of the river on either side. In others, braces are set in the ice, at short intervals, before the channel is opened, as shown in the illustration. The posts should be heavy, and the cross struts may be ten or twelve inches square. The post holes, if cut oblong, will allow short boards to be spiked to the sides of the posts at their lower ends. When inserted through the ice, a quarter turn of the post will bring the projecting ears under the ice, and no trouble will be given by the post raising out of its place. The cross strut should just allow the ice to float beneath, and be well secured to the posts, which require inclined braces, joining the posts opposite the ends of the struts, with their feet planted in recesses cut into the ice. Water should be poured around the braces, and when the braces and posts are frozen in place a very strong support is secured against the current, as the following cut shows.
FIG. 15. BRACES FOR CHANNEL WITH SWIFT CURRENT.
Where the current is not so strong, square frames may be employed. They are placed in the channel where the ice cake will float through freely; their sides should fill mortices in the sides of the channel, and not project into the path of the cakes, as shown in [Fig. 16].
Various methods of dealing with cracks in the ice have been tried. A good one is to take long planks and extend them across the cracks laying flat on the surface. By boring through the planks into the ice, and inserting wooden pins, the loosened portion is firmly held, and the cracks will freeze up. If the pins are inclined in opposite directions a firm hold is secured on the ice.
When the channel has been located, if convenient, a deep groove is plowed at either side, and the remaining ice is cut away with the pond ice saws. Splitting chisels are now brought into play, and the ice in the channel is split up into cakes, which are sunk and floated under the ice. Canals through the plowed field are similarly opened. The field is now in readiness to furnish a supply of ice cakes for stowing in the house.
FIG. 16. BRACE FOR SLOW CURRENT.