§ 2. Classification of transportation corporations. A transportation corporation shall be either,

1. A gas corporation, an electric corporation or a gas and electric corporation.

2. A telegraph corporation, a telephone corporation or a telegraph and telephone corporation.

3. A water-works corporation.

5. A ferry corporation.

6. A pipe line corporation.

7. A freight terminal corporation.

8. A district steam corporation.

9. Sewage-works corporation.