EXPERIMENTAL RESEARCH ON SEVERAL TYPES, ETC. 7 
ceding one. The numerical entity of the deviations is an index of how two subsequent 
models have been linked together. However, we wish to point out the scale 
transfer equations already impose that the deviations be as small as possible in 
1, 3, 6 of the 9 points placed in the above mentioned overlapping zone. 
In table 1 an example is given of the way in which strip i B parallaxes and 
deviations have been collected, in order to study how they vary from one type 
of computation to another. Each one of the numbers written therein represents 
the mean square value either of the residual parallaxes in each model, or the 
mean square value of the X, Y, Z deviations in the overlapping zone between two 
consecutive models. 
The mean parallax per model comes from the arithmetic mean of 6 numbers 
for the computations 6-1, 6-3 and of 18 numbers for the computations 18-1, 18-6, 
while the mean deviation always depends on 9 values : in fact, in all four types of 
bridgings we have plotted all the 18 points belonging to each model, 9 of which 
are in common to the following one. In the last column are shown the means rela 
tive to each strip (M x ). The values are expressed in cm on the ground : each cm 
on the ground represents about 0,8 \im on the plate. From the five strips and from 
the two measures A and B, 10 tables similar to table 1 have been deduced ; from 
Table i 
MEAN SQUARE VALUES 1 B (in cm) 
Residual parallaxes 
Model 
i 
2 
3 
4 
5 
6 
7 
8 
9 
M x 
Computation 
6-1 
9 
4 
i 
6 
2 
3 
2 
7 
0 
4 
6-3 
9 
5 
2 
6 
3 
6 
10 
12 
5 
6 
18-1 
10 
9 
10 
9 
6 
9 
7 
9 
8 
9 
18-6 
10 
13 
11 
9 
8 
ii 
ii 
10 
9 
10 
X deviations 
6-1 
6 
2 
3 
2 
2 
25 
6 
4 
6 
6-3 
5 
3 
3 
3 
3 
14 
2 
2 
4 
18-1 
4 
2 
5 
4 
3 
23 
2 
3 
6 
18-6 
2 
2 
3 
2 
2 
12 
2 
2 
3 
Y deviations 
6-1 
36 
16 
16 
12 
18 
41 
20 
30 
24 
6-3 
34 
12 
16 
14 
22 
29 
6 
13 
18 
18-1 
31 
16 
20 
22 
21 
46 
5 
21 
23 
18-6 
20 
H 
16 
12 
U 
28 
5 
12 
15 
Z deviations 
6-1 
56 
38 
30 
25 
27 
78 
41 
45 
41 
6-3 
48 
24 
29 
27 
30 
53 
19 
22 
31 
18-1 
60 
29 
38 
38 
35 
87 
20 
30 
42 
18-6 
34 
23 
27 
24 
26 
53 
19 
16 
28