viii CONTENTS. 



CHAPTER III. 



4>UMPS. ATMOSPHERIC RAILWAYS AND LETTER TUBES. 



PAGE 



I. Pumps. Atmospheric Pressure employed in tlie Elevation of 



Water 50 



II. Fire-engines 58 



III. Pneumatic Machines, or Gas or Air-Pumps 63 



IV. Atmospheric Railways 64 



CHAPTER IV. 



INDUSTRIAL APPLJCATIONS OF COMPRESSED AIR. 



I. The Air-Gim . . 69 



II. The Boring of Tunnels by Compressed Air 71 



III. Compressed Air Posts Compressed Air Railways 77 



IV. Use of Compressed Air in Bridge Building 82 



V. Measuring Heights by the Barometer "... 84 



CHAPTER V. 



BALLOONS AERIAL NAVIGATION. 



I. Application of the principle of Archimedes to the Vertical Ascension 



of Bodies in the Atmosphere 87 



II. Montgolfieres, or Hot-air Balloons, and Gas-BalloonsConstruction 



and Filling 91 



III. Application of Aerostation to Military Purposes, to the Study of 



Meteorology and Terrestrial Physics 99 



