L37 



CONTENTS. 



COMMOH THINGS. AIE. 



PAGE 



1. Air most necessary to existence. 2. Respiration. 3. Fresh air 

 necessary. 4. Air is material. 5. Its weight and momentum. 

 6. How weighed. 7. The atmosphere. 8. Its pressure. 9. 

 Why bodies not crushed by it. 10. Illustrated by a cupping-glass. 

 11. Compressibility. 12. Elasticity. 13. Elastic pressure. 

 14. Varies with the density. 15. Strata of atmosphere near 

 the surface of the earth and at greater elevations. Diminished 

 pressure at great elevations. 16. Anciently supposed to be an 

 element. 17. Air a compound. 18. Gases. 19. Proportion of 

 the constituents of air. 20. Azote or nitrogen. 21. Oxygen gas. 

 22. Combustion. 23. Its products. 24. Carbonic acid. 25. 

 Unfit for respiration. 26. Impure air produced in wanning and 

 lighting. 27. Ventilation of public buildings. 28. Carbonic acid 

 in effervescing liquors. 29. Is generated in all spontaneous 

 changes of dead matter. 30. Choke-damp. 31. Is diffused 

 through the atmosphere. 32. Evolved in respiration. 33. Vital 

 air. 34. Air poisoned in crowded rooms. 35. Necessity of 

 ventilation. 36. Air not absolutely transparent or colourless . 1 



LOCOMOTION BY RIVER AND RAILWAY IN THE UNITED STATES. 



CHAP. I. 1. Natural apparatus of internal communication in United 

 States. 2. Canal navigation. 3. Erie Canal. 4. Extent of 

 canals. 5. Total cost, and cost per mile. 6. Extent of canals as 

 compared with population. 7. River and coast navigation in 

 United States. 8. Steam navigation on Hudson. 9. Tables of 

 Hudson steamers. 10. Beautifully finished machinery and 

 structure. 11. Their great speed. 12. Application of expan- 

 sive principle. 13. Explosions on eastern rivers rare. 14. 

 Description of paddle-boards and mode of working steam in 

 steamers of eastern rivers. 15. Power of engines. 16. Fares 

 reduced with increased size of vessels Form and structure ot 

 Hudson steamers. 17. Description of the navigation of that 

 river. 18. Steam navigation of other American rivers. 19. 

 Mississippi steam -boats. 20. Cause of explosions. 21. Mag- 

 nitude and splendour of boats. 22. Extent of the navigation of 

 the Mississippi valley .17 



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