If the glass is turned into the position shown in figure 33, the small plus lenses, just in front of the eye pieces, drop automatically into position and reduce the power to 3.8 diameters, and increase the field to 8.3 degrees. This position requires a different adjustment, the tubes being drawn out about one-third of an inch to get the proper focus. It will be observed in the illustrations that the rear bar of the frame is not only lettered to indicate which power is being used, but the bar itself is shaped with a hump on one side, and hollowed on the other. When the hump is up, the low power is in use. This is to facilitate adjustment in the dark. The action of the small automatic lenses is free and positive. _Neither the eyepieces nor the sections containing the small lenses should be unscrewed, except in case of necessity, and then not by unskilled hands._ [Illustration: FIG. 33.--Signal Corps field glass, Type A.] The frame, of aluminum and brass, is composite, to give lightness and strength; and while it is constructed to withstand the rough handling of field service, no field glass is proof against careless or wanton treatment. The tubes are covered with tan leather, and a round sling cord, braided from four strands of pliable tan leather, is fastened by snaps to eyes in the frame. The case is of tan calfskin, provided with shoulder strap, and has an efficient small compass set into the cover. Two loops are sewed to the back of the case so that it may be worn on a belt. The glass, complete with case, cord, and straps, weighs 21.5 ounces. Two of these glasses are issued to each company of infantry and coast artillery, Philippine Scouts, and Signal Corps, and to each troop of cavalry for use in instruction in visual signaling. Below is a brief description of the type A glass. Magnification, 3½ and 5½ diameters; Galilean type; object lens, 1½ inches; tan leather finish; tan leather carrying case with compass; weight of glass, complete, with case, cord, and strap, 25 ounces. At a distance of 1,000 yards the field of view includes a diameter of 123 yards for the 3½ power, and 73 yards for the 5½ power. Length of glass closed, 4 inches. This glass is issued as a part of the visual signaling kit to each company of infantry, coast artillery, and Philippine Scouts, troop of cavalry, machine-gun platoon, and Signal Corps field company. Price, $12.15. The latest issue of this glass known as the Type A, model 1910, includes provision for interpupillary adjustment, the two barrels being hinged to accommodate the glass to the distance between the pupils of the eye. The price of the model 1910 glass is $14.75. Type B: This field glass is similar in appearance and construction to the Type A glass, and is issued to the field artillery organizations upon requisition. The following is a brief description: