Oct., 1935.1 CURRENT TOPICS. 531

It is constructed so that 8 ft. to 9 ft. lengths of lumber, pipes and other supplies can be handled easily. The skis are especially constructed and adapted to local conditions of deep snow. They are also rigged to obtain maximum efficiency in turning around in small spaces, and for quick take-offs on short landing spaces. A long, narrow ski, with a long, sloping turnup both fore and aft of the ski pedestal has been found most efficient. The bottom of the ski is lined with No. 22 gage black iron which gives considerable strength to the ski, and does not cling to damp snow. Extra strong rubber shock cord is attached on the nose of the airplane to the nose of the ski to help raise the skis out of the snow on the take-offs. The ski is constructed so that the axle is 37 per cent. of the distance from the heel of the ski to the nose of the ski. During 1934, more than 60 tons of mining machinery and supplies were transported to the mining properties by airplanes without any damage or loss. These supplies included everything necessary for the development and putting into production of two mines.

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Insulated Cars for Shipment of Dry Ice.-(Railw,ay Age, Vol. 99, No. 6.) Five such cars of the A. A. R. Class Rc have recently been built by the American Car and Foundry Co. for the Liquid Carbonic Corporation, Chicago. They are 45 ft. long and of steel construction throughout. The entire bottom half consists of a solid bed of insulation surrounding the steel bins provided to hold the dry ice. Up to a height of 8 ft. above the rail the width is IO ft. 8 in. From this point the sides are tapered in to a width of 8 ft. II in. at the eaves which are 13 ft. 3 in. above the rail. These dimensions were adopted in order to provide maximum lading and insulation for the container bins, sufficient inside head room for the men engaged in loading, and at the same time to provide adequate clearance for tunnels, etc. The load limit of the cars is 79,500 lbs. The actual loads will be approx. 30 tons. The insulated sides are provided with ventilating louvers near the eaves. The central side doors are of the sliding type and extend only half way down the sides. Insulating materials are cork and balsam wool and fir wood sheathing is used for outside of the steel bins. The tops of the bins are open, but when in service are covered with an 8 in. flexible blanket of kapok. These cars will transport dry ice from manu- facturing to distributing points with relatively small losses.

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A Refrigerated Slot Machine.-C. A. RODMAN of Detroit, Mich., describes his development in part, for the Cincinnati Ball Crank Co..