Ing. Nistri gets thus rid of the restraints represented by the ties cf
th» mechanical transmission, which are sometimes a source to remarkabie
difficulty, and consequently he makes the adjustments of the coordinato-
meter carriages easier.
As it will be suitably illustrated in the following chapters this new
principle, representing a generalization of Porro's principle and further-
more the introduction of the whole transmission by means of electro-ma-
gnetical systems, give the instrument a particular character, make its ad-
justment and manufacture easier, and — what is undoubtedly a remark-
able fact — allow to carry out at the same time several cartographies,
i
Scamottaggio
triang. spaziale
Pr. Amici D, J GN "ny
$mezzamento ,
verticale
$mez2amento
orizzontale
Distanza
oculari
a
$
Piccoli
spostamenti à | To d #0.
Piccoli 5 ; :
spostamenti £Q
X Disegno
X Modello m i En
> : 3 3 ; Relais
Z Modello
Y Modelo
Yo isegno Inter, ‘
Fig. 4 — Smezzamento = correction for coincidence; verticale — vertical; orizzonta-
le = horizontal; Distanza oculari = distance eye-pices; Piccoli spostamenti — small dis-
placements; Disegno — drawing; Modello — Model; Scamotaggio triang. spaziale — com-
mutation unit special triang; Pr. Amici = Amici prism; Interr. = switch.
even at different scales, on cartographic tables placed even at a remark-
able distance to each other, in the same room, or even in different rooms.
In the following chapters is given a short description of the Photo-
stereograph. In another paper it will be related about the pratical re-
7