Was iron used to make the railroad?
Yes, the railroad is made of iron.
    src        edge_attr  dst
0     0               on    1
1     0  to the right of    7
2     0  to the right of    6
3     0   to the left of   10
4     0               on    4
5     0   to the left of    5
6     0  to the right of    3
7     1   to the left of    4
8     1   to the left of    5
9     3   to the left of    0
10    3               by    7
11    3  to the right of    7
12    4  to the right of    1
13    4   to the left of    5
14    5  to the right of    9
15    5  to the right of    8
16    5  to the right of    4
17    5  to the right of    0
18    5  to the right of    1
19    5               on    4
20    6   to the left of    8
21    6   to the left of    0
22    7   to the left of    0
23    7   to the left of    3
24    7   to the left of    8
25    8   to the left of   10
26    8  to the right of    7
27    8  to the right of    6
28    8   to the left of    5
29    9   to the left of   10
30    9   to the left of    5
31   10  to the right of    9
32   10  to the right of    8
33   10  to the right of    0