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équivalent arrangé dans la chambre, et par un miroir, manœuvré par le gyros 
cope à 1 aide de systèmes de leviers suffisants à assurer la reproduction 
fidèle de 1 orientation spatiale de l’axe de rotation rapide du gyroscope, 
grâce à leur masse extrêmement petite et à leur docilité de mouvement. 
L'indication du repère sur le photogramme, outre qu’automatique, est 
aussi dégagée des erreurs inhérentes aux opérations auxiliaires de calcul ou de 
transport graphique, la dite indication étant seulement affectée par les erreurs 
strictement inhérentes au fonctionnement du système gyroscopique. 
Finalement, l’auteur expose les résultats de certaines expériences pra 
tiques d’application du dispositif. 
DEVICE FOR RECORDING DIRECTLY ON THE PHOTOGRAPH, 
AT THE MOMENT OF EXPOSURE, THE NADIR POSITION 
by Dr. G. Parenti 
The Author describes concisely the various solutions devised to date in 
order to record on the photograh those geometrical elements which are 
necessary in order to determine the orientation of the principal axis of the 
taking camera with respect to the vertical line, as represented by the lines 
of force of the terrestrial gravitational field. 
After remembering that all proceedings known so far furnish but 
indirect elements which still require to be elaborated in order to achieve that 
determination which is really interesting, i. e. the spotting of that point of 
the terrain corresponding to the nadiral point, the Author describes a simple 
optical device realized by the Firm O.M.I. — Rome actuated by a gyros- 
copical system, which produces directly and without the need of any compu 
tation or graphical transportation, a small cross on the photogram in corres 
pondence to the nadiral point. 
The system is made of a collimating group, the last element of which 
is represented by the recording camera lens or by an equivalent one, displa 
ced within the camera, and by a mirror actuated by the gyroscope through 
opportune arms sufficient to insure the faithful reproduction of the spatial 
orientation of the gyroscope axis of rapid rotation in virtue of their small 
mass and their docility of movement. 
The reference indication on the photogram, beside being automatical, 
is thus freed from the errors incidental to the auxiliary operations of compu 
tation or graphical transportation, and there remain only the ones closely 
inherent to the operation of the gyroscopic system. 
Lastly the author exposes the results achieved in some practical expe 
rimental applications of this device.