The Montgomery advertiser., 1905-05-21
camera may be found for any given height and distance of object.
 Making Observations.

camera may be found for any given
 height and distance of object.
 Making Observations.
 "Refore the apparatus is allowed to ascend, the other observations are to pc made. The first consists of determin- ing the prevailing direction of the wlno and the second has for its object the determination of the bearings or the distant object in angular measurement This latter is determined merely oy the observer directing his telescope In azl-
 muth until the vertical cross hair cuts the distant fort and reading off the angular movement from the scale. We will assume the wind to come direct from the north and that the distant oo- feet bears due west, as represented py
 an angle of ninety degrees. "It remains now only to set the wind vane in azimuth at an angle or ninety degrees with optical axis, and to allow the apparatus to ascend, heed being
 given to the tally-morks on the flexi-
 ble cable as it Is fed out. When one
 thousand feet of cable have been fed out, the apparatus is anchored. "In order to make a photographic negative, the observer first points his
 telescope directly toward the fort clamps the instrument in azimuth; then points it toward the suspended camera
 and clamps it in altitude. The obserV- CT, looking through the right-angle ocular, will see the suspended apparat- us in the field of view, the aluminium sighting balls crossing and re-crosslng the vertical cross hair of the ocular as they oscillate In the air. The suspend ed wind vane will take up general position parallel to the wind-uorth and south. and since the sighting balls have been placed at an angle of ninety de- l | xNyfll nninf west and east, and since the optical system
 has been given an inclination of forty five degrees to the horizontal, the lens will point directly toward the distant | fort.
 Moment for Exposure.
 The observer, watching the sighting ' balls passing the vertical cross hair or
 the ocular. finds a moment when both spheres cut the hair. He then presses
 a key, and a fresh surface is presented | for the next exposure.
 | ITO secure a panoramic picture we
 proceed in much the same way. Know : | ing the angle which the photographic 1 lens in use sustains upon the sensitive
 plate of given dimensions, the observer | determines how many times this angie
 is contained in the length of panorama he desires to secure. It is then only
 necessary to shift the telescope in azi-
 muth in successive extents equalling l the angle of the lens, and to make sue
 cessiVe exposures at each position, the
 resulting negatives slightly overlap ping. Prints from these negatives,
 when trimmed and pasted end to end,
 form the panoramic picture sought. Tt makes no difference how much | the camera is caused to swing by the
 wind when suspended in the air, be- cause the observer has only to select
 moment when the camera, in it's swing, presents both sighting balls simulta- neously on the cross hair of the teIe- scope, when he presses the key and registers an exposure.
 obviously photographs obtained when the lens makes a considerable angle with the horizontal will be dis torted, all vertical lines in the photo graph appearing to converge toward the bottom. But this distortion is Of no importance whatever, and since the distortion takes place in conformity 10 well known laws, it may be entirely corrected when enlarging the mega tives, by the ordinary photographic methods.
 Calculation of Distance.
 Suppose the negative secured in the first instance shows, in addition 10 the desired details. as to the extent and character of the military works, the presence in harbor lying beyond the fort. of a battleship or other vessel ol
 war. Now it is possible from the pho tograph, to calculate the distance and
 the bearings of the vessel, although entirely shut out from view by inter vening objects, and since every ord nance officer knows the curvature or traject tory and other constants or every | gun in his artillery train, he would at
 once be in a position to single out the | battleship for attack. with the chances greatly in facor of landing an effective fire. Similarly, any other object dis