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

717

and the principal lines upon the perspectives, but they also give the means to discover any distor-tion that may arise in the pictures due to the wet process of development.

This métal graduated frame is brought into contact with the sensitive surface of the film by a simple mechanical contrivance in such a way that the focal leugth for ail négatives is constant, even if the plate holders or glass plates should not be equally thick.

(6) Col. A. Laussedafs latest phototheodolite.—This instrument (figs. 105 and 106) has been manufactured by E. Ducretet and L. Lejeune, in Paris, France.

Both transit telescope L and caméra G are centrally mounted, the latter above the former. The caméra may also be used alone, independently of the transit, and it may then be mounted upon the tripod (fig. 106) by means of a spécial pivot or spindle 8'. The transit may likewise be used alone, without the caméra, for trigonométrie observations.

8 = leveling screws. cx == central clamp screw. G = caméra, and B = magazine for fifteen plates. O = objective of the caméra; it is a rectilinear wide-angle lens of 75 millimétrés focal length. R = sliding front plate of caméra, provided with pinion and rack movement, P, to elevate or depress the lens. V = finder to show the extent of the field covered by the photographie plate, although a focusing glass, G, fig. 106, is also provided. L = transit telescope provided with stadia wires. Ce = vertical circle, graduated to 30'. M = Wye supports of the telescope axis of révolution, their prolongation forming the caméra support. A = horizontal circle graduated to 30' ; its clamp and slow-motion screw are indicated at P'. N = adjustable level.

D = déclination or box compass.

Several loaded magazines, each containing 15 plates, may be carried with this instrument and the plates may be exchanged in full daylight without having to remove the caméra. The photographie plates are 6^ by 9 centimètres, but enlarged prints are

used for the iconometric platting.

Six plates cover the entire horizon and will form a complété panorama.

The lens is provided with an iris shutter. It may be focused for

short distances or infinity by turning a lever over a scale showing the distances in métrés attached to the front board, R, of the caméra.

In fig. 106 the caméra is represented with the magazine, B, removed and replaced by the ground glass plate, G.

The entire outfit, excepting the tripod, may be transported in one carrying case (with shoulder or pack straps) of 39 by 28 by 17 centimètres size and 8 kilogrammes weight if but one magazine filled with 15 plates is included.

(7) The phototheodolite of Starlce and Kammerer.—This instrument, fig. 107, is somewhat similar in construction to Professor Finsterwal-der’s phototheodolite; both hâve neither telescope nor vertical circle, being provided with caméra télescopes instead.

An ordinary skeleton tripod supports the three leveling screws, 8, and a central clamp screw with spiral spring, P, securely connects the tripod head with the instrument proper. R represents the horizontal circle, graduated to 20', but by means of two verniers and microscopes, L, horizontal angles may be read to 1'.

The vertical axis of révolution, ending in three horizontal afms, B2, P3, may be adjusted with the aid of the leveling screws S and the cross levels lu l2. The plate P, forming the support of the cross levels, is firrnly united with the arm B2.



F«g. t OS

Fig. I 06

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