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86 are liable to be struck and must be protected. The best possible protection is to place the whole of the machinery and the apparatus connected to the cable into an iron house. It is not necessary that the walls of the house be entirely made of iron. In Milan there is such a house for the protection of the junction of the overhead power lines coming from the Alps, and joining by means of certain apparatus with the underground cable network that supplies the town with electricity. In appearance this house is not different from any of the other factory buildings of the neighbourhood; nevertheless it is a Faraday Cage. The roof has an iron lining, the stanchions are well bonded with it and with each other, and go down to the moist subsoil. Below the plastering of the walls is a heavy expanded metal lining all connected to the roof and stanchions, and the windows have iron frames also in good electrical connection with the metal walls. The building thus forms a metal shell, and affords complete protection to its contents against any electrical disturbance from outside.