Supplement to Machine Gun Drill Regulations (provisional) 1917 and Provisional Machine Gun Firing Manual, 19171918 - 354 pages |
Contents
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Common terms and phrases
20 meters accurate adjustment aiming point aiming post aiming target alidade angle of fall Appendix artillery auxiliary aiming mark barrage fire barrel beaten zone bullet clamps clearance clinometer combined sights compass contours correction dial directing gun distance drill emplacements enemy enfilade error eyepiece field glass fire effect firer flank guns friendly troops front goniometer graduation grid bearing ground gun commander gun lays gun level gun position gunner horizontal Hotchkiss machine gun indirect fire infantry instrument laid lay the gun length line of aim line of fire line of sight machine gun fire magnetic measure ment meters method mil scale mils Right mounted needle observation obtained parallax parallel pivot placed plane table Porro prism prism protractor quadrant elevation rear sight reference object reverse slope sight setting tangent elevation telescope tion trajectory traversing trench trench warfare tripod True North vertical zero line
Popular passages
Page 217 - The most important and essential quality of a glass is definition, ie , the sharpness, clearness, and purity of the images seen through it. To obtain good definition it is necessary that spherical and chromatic aberration be overcome, that the polish of the lenses be as perfect as possible, that the cement possess no inequalities, that the lenses be well focused, that there be no dampness in the interior of the tubes, and, generally, that the instrument be without optical defect. Faults in this direction...
Page 271 - ... oriented. Resections upon the extreme points intersect on this line and determine the position of the point sought. In Fig. 60, let a, b, c be the platted position of the known points ; the plane-table being set up on the unknown station D and leveled, the alidade is set on the line ca, and the end at a is directed, by revolving the table, to its corresponding signal A, and the table clamped; then, with the alidade centered on c, the middle point...
Page 261 - Compass Errors. Irregular variations due to so-called magnetic storms are uncertain in character and cannot be predicted or estimated. Such variations are sometimes large. Local attraction due to the presence of iron and steel objects or iron ore deposits in the ground greatly disturb the needle and often come from unknown sources. The observer should have them constantly in mind and should not use the instrument in the immediate vicinity of such magnetic influences as electric wires, railroad tracks,...
Page 259 - Dip. A symmetrical needle tends to point downward toward the magnetic pole of the earth. This displacement from the horizontal is called dip. The needle must be kept horizontal and, to overcome the dip, a small counterweight is placed on one side of the needle so that it can be moved in or out until the needle is balanced. In the Northern Hemisphere this counterweight will be on the south end of the needle. For considerable changes of latitude...
Page 217 - ... discovered at once by examination of definition, whereas in determining the other constants they are less noticeable. In comparing the definition of any two instruments it is ordinarily necessary only to scan distant objects and observe to what extent details may be distinguished. The following test may also be used: Focus on printed matter at a distance just beyond that at which perfect clearness is given and gradually approach until the letters are distinctly defined. The instrument with which...
Page 89 - ... the three angles of a triangle are together equal to two right angles, although it is not known to all.
Page 261 - Abnormal deflections of the needle, due to local disturbances, are sudden and erratic and should not be distributed among all the courses, but only among those In which there is reason to believe the disturbance occurs. A simple way to detect — not measure — such disturbances Is to take frequent back azimuths. If the position of the needle is normal at both stations, the azimuths and back azimuth will differ by 180°.
Page 63 - ... from which a large volume of fire can be delivered by a few men. This characteristic enables the automatic rifle to meet an attack from any direction with little or no movement or exposure. A sudden attack from the flank can be dealt with at once. This indicates -the usefulness of the automatic rifle on a flank, in a detached post, in a salient, or for engaging in an enveloping attack; it can carry out these missions without increasing its vulnerability to enfilade fire as would be the case with...
Page 217 - ... that the lenses be well focused, that there be no dampness in the interior of the tubes, and, generally, that the instrument be without optical defect. Faults in this direction are discovered at once by examination of definition, whereas in determining the other constants they are less noticeable. In comparing the definition of any two instruments it is ordinarily necessary only to scan distant objects and observe to what extent details may be distinguished. The following test may also be used:...
Page 271 - Then, with the alidade centering on a, the telescope is directed to the middle signal, B, and the line ae is drawn along the edge of the rule. The point e (the intersection of these two lines) will be in the line passing through the middle point and the point sought. Set the alidade upon the line be, direct b to the signal B by revolving the table, and the table will be in position. Clamp the table...