142 
THE TELEGRAPH. 
the sides of the tunnel by troughs, at the springing of the arch, 
supported by wrought-iron fixings. These fixings are placed 
about every yard, and such of them as connect two adjoining 
troughs are nearly twice as wide as the others (fig. 86). 
The cables that pass through tunnels are joined to the aerial 
wires through boxes or posts, at which examinations can easily 
be made for the detection of faults. 
The following is the arrangement adopted in Belgium in 
these testing boxes, and it answers all requirements, either on 
the score of insulation or on that of durability. 
Fig. 85. Fig. 86. 
A cast-iron bracket (fig. 86) fixed into hewn stone by 
bolts, secured with lead, supports an oak board, on which is 
fastened a vertical plate bearing the screws. A sheet-zinc 
case protects the plate, and rests on the top of the bracket, 
where it fits tightly on the wooden base of the oak board, to 
which also it is fixed by screws. 
The wires enter the box by two openings at the foot. 
As the box is removed from the surface of the wall by the 
bracket, it is quite impossible for moisture to get inside the 
box. 
When submarine cables have to be connected to the 
operating station, the marine line is always made to terminate 
in a special building, called in England the “ cable house,” 
and in this electrical tests are applied every week, to indicate 
the condition of the submarine line. 
At Marseilles, there are two small buildings devoted to this 
purpose by the Eastern Telegraph Company, and situated near 
the entrance of the Borely park, and on the banks of the 
Huveaune. These two buildings, one on the right and the 
