Canals Railroads 51 Law and legislation 13 Navigation 12 History 11 Costs 8 Design and construction 7 more ... Early works to 1850 7 Canaux 6 Public works 6 Rates and tolls 6 Coal trade 5 Finance 5 Inland navigation 4 Lotteries 4 Water-supply 4 Appropriations and expenditures 3 Banking law 3 Governmental investigations 3 Internal improvements 3 Locks (Hydraulic engineering) 3 Railroad law 3 Surveying 3 Taxation 3 Transportation 3 Coal 2 Coal mines and mining 2 Commerce 2 Maintenance and repair 2 Pennsylvania imprints 2 Power utilization 2 Rates 2 Rules and regulations 2 Telegraph 2 Tolls 2 Water-power 2 Women in the book trades 2 %CHR 1 1834 1 Aeronautics 1 less ...