REPORT FOR 1897--PART II. APPENDIX NO. 10.

715

on the scale and vernier M, fig. 100. The pneumatic caméra shutter is arranged both for time and for instantaneous exposures, a spécial device guarding against the possibility of exposing a plate before it is brought into perfect contact with the graduated métal frame, previoasly mentioned.

The plate holder can not be withdrawn from the caméra before the slide h as been replaced, nor as long as the plate is in contact with the graduated frame.

(4) The phototheodolite of Dr. G. Koppe.—Dr. O.

Koppe, professor at the Technical High School in Braunschweig, Germany, is an ardent advocate of pho-togrammetry and he has done much toward populariz-ing photographie surveying in Germany. His work on photogrammetry, published in 1889, is an excellent mannal both in respect to theory and practice. In 1896 he published a treatise on photogrammetry applied to cloud photography for meteorological research.

This phototheodolite, fig. 102, has a centrally mounted caméra with the telescope on one side and the vertical circle on the other. The horizontal axis between the two wyes has been widened into a conical ring R, into which the caméra G may be inserted. Four stout springs f press the caméra G tightly against the ring surface forming the base of the conical ring R.

After insertion into the ring, the caméra G is revolved witliin the former until the end of the screw 6 abuts against the stop d, when the horizon line of the perspective (négative) should be horizontal.

The caméra axis is parallel with the optical axis of the telescope T, both axes being in the same horizontal plane when the vernier of the vertical circle reads zéro. When elevating or depressing the telescope T the caméra axis will follow the

same motion, both remaining parallel. The instrument will be in equilibrium with the caméra de- or attached. The horizontal axis of this instrument may be adjusted by means of the striding level A, which, when necessary, may be replaced by a striding compass in a manner similar to that illustrated in fig. 101.

Since the telescope may be reversed in the wyes, an error of collimation and any index error of the vertical circle may be found or eliminated.

There are neither slides nor plate holders provided with this instrument, the plates being inserted directly into the caméra. This may be done in the field by aid of the packing case specially constructed to serve as a dark chamber, fig. 103.

This case is made of wood with double doors, each door having a circular hole A, which is filled in with a flexible, light-tight, and dark-colored material, forming sleeves in such a way that the hands of the operator may be thrust through an elastic opening in the center (of the

1_______________________

Fig. I 03

---

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 96,65 %.

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

---