100 MOTION OF A SPINNING BODY
has steered the torpedo through the predetermined angle, that is till the line from the center of the cam-disk to the center of the square part of the cam is parallel to the axis of the torpedo. From that moment, the torpedo will be steered in a straight course.
The Dieter* method of angle fire is to keep the cam-disk fastened to the gyroscope so that the line from the center of the disk to the center of the square part of the cam remains parallel to the gyro spin-axle, and turn the entire gyroscope through the required angle about an axis perpendicular to the torpedo axes. The operation is similar to that of the preceding method.
Other methods for producing angle fire have been devised by Kaselowsky, Waldron, Patterson, Blountt and others.
A torpedo proceeding along a straight course has but one chance to hit a given target. If, however, after reaching the neighborhood of the target, the torpedo be caused to go around and around in circular paths, then there are more chances of a hit. Devices to cause a torpedo to proceed on a straight course for a predetermined distance and then execute circular paths have been developed by several inventors.$
61. Airplane Cartography. - During the Great War methods were developed by which military maps were made from a series of photographs taken by a camera mounted on an airplane. As the airplane moved back and forth in parallel paths, the camera took a series of overlapping views on a long film which afterward could be cut up and fastened together so as to form a mosaic of the district covered. The points which were common to overlapping parts of successive pictures served to bring the separate pictures into register and also to show any difference in scale of successive pictures.
Since the war, the method has been greatly improved and its use extended to civil operations. It is estimated that over rough terrain one camera on an airplane can take in one hour the pictures for a reconnaissance map that would be as accurate and detailed as the data that would be taken in one month by a party of one hundred surveyors.
In order that all the pictures in a strip may be on the same * U. S. Patent. Dieter, No. 1153678, 1915. f U. S. Patents. Kaselowsky, No. 661535, 1900; Waldron, No. 983467,
1911; Patterson, No. 1332302, 1920; Blount, No. 1527777, 1925.
t U. S. Patents. Dieter, Nos. 1303038 and 1303044, 1919; Meitner and May, No. 1401628, 1921; Trenor, No. 1517873, 1924; Bevans, No. 1527775, 1925.