716

UNITED STATES COAST AND GEODETIC SURVEY.

circular openings). The fabric will close tightly around tlie wrists—when the interior of the case will be perfectly dark—and the sleeves A will permit free play to the hands for manipulating the caméra and plates within the space L of the case.

This case is inclosed with a tight-fitting sole-leather covering, having two flaps S to protect the openings A against the admission of dnst when the packing case is transported on the baek of the instrument bearer.

The entire instrument, except the tripod, may be packed into this case for transportation. It also contains two boxes, Ki and the former receives the exposed plates (négatives) while the lutter contains the supply of unexposed plates.

When a plate is to be exchanged the caméra G is placed into the packing case and both doors as well as theleather main flap or cover are securely closed ; both hands are now inserted through A, and after the sleeves are tightly closed about the wrists the caméra is opened, the exposed plate removed and placed into the box Kx (as shown at P, fig. 103). The door T is closed and a new plate, taken from the box K2, is placed into the caméra (as shown by g, fig. 103) and the caméra back is closed, when the caméra will be ready for another exposure.

The constant focal length of this caméra is represented by the distance between the second nodal point of the lens and the rear surface of a métal frame (similar to that of Ney’s photo-theodolite) permanently attached to the rear of the caméra box.

The inner edges of this métal diaphragm or frame are graduated into centimètres; the middle

graduation marks of the horizontal sides of the frame locate the principal line, while the middle graduation marks of the vertical sides represent the termini of the horizontal line on the perspectives. The focal length, once determined, will remain unchanged for a 11 plates.

This instrument has been manufactured for Professor Koppe by F. Randhagen, in Hanover, Grermany.

The “Topographie Bureau” of the Swiss Republic has used a phototheodolite constructed after the model of Dr. Koppe’s instrument. The expérience in Switzerland, however, seems to hâve decided the topographie bureau not to replace the plane table by the phototheodolite for general topographie surveys executed by that bureau.

(5) Phototheodolite devised by V. PollacJc, manufactured by B. Lechner in Vienna, Austria.—With this instrument (fig. 104) the caméra O is centrally located, and it rests ux>on a horizontal circle. The telescope F and the vertical circle are mounted at one side of the caméra, a weight G counterbalancing both on the other side of the caméra.

Aluminum has been used very freely in the construction of this phototheodolite in order to reduce the weight as low as possible. This instrument has been manufactured in two sizes; the horizontal circle of the small sized one is graduated to 30', the verniers reading F, while the larger one has a circle graduated to 20', and its verniers read 20//. The telescope F is mounted similarly to that of the so-called Danish plane table alidade.

The adjustment of the horizontal axis of révolution of the telescope F is accomplished by means of a spécial level. Clamps and slow motion screws are provided for both the horizontal and vertical circles. The telescope has a focal length of 27 centimètres and an opening of 31 millimétrés, with a magnifying power of 9 to 18 diameters. The telescope is arranged for stadia reading, and it has 100 as the constant multiplier. The telescope level L is graduated to 10" or 20". The vertical circle is graduated to 20' and its two verniers read to 20".

The caméra box is made of aluminum and it is provided with a Zeiss anastigmat. By means of the rack and pinion z the lens may be elevated or depressed by either 30 or 50 millimétrés, according to the size of the instrument. The scale t, with vernicr serves to measure the vertical déviation of the lens from its normal position. Also this caméra is provided with a graduated métal frame, the inner edges of which hâve either a centimètre or five-millimétré graduation, winch is reproduced upon the margins of the négatives. They serve not only to locate the horizon

---

Le texte affiché peut comporter un certain nombre d'erreurs. En effet, le mode texte de ce document a été généré de façon automatique par un programme de reconnaissance optique de caractères (OCR). Le taux de reconnaissance estimé pour cette page est de 96,25 %.

La langue de reconnaissance de l'OCR est le Français.

---