Vlll CONTENTS. 



Page 



The air-pump 129 



Of condensed air 145 



The barometer 147 



Practical directions for using the air-pump 152 



The air gun 157 



The diving-bell 159 



Air balloons 162 



Of the winds 172 



HYDRAULICS 176 



The syphon 179 



Pumps 182 



Steam engine 106 



Steam boats 225 



OF SOUND , 227 



OPTICS 232 



Of refraction 234 



Focal distances of lenses 243 



Refrangibility of the rays of light 247 



Description of the eye and nature of vision 249 



Of spectacles 257 



Of reflection 261 



Microscopes 271 



Telescopes 297 



The multiplying glass 311 



Camera obscura 312 



Magic lantern and phantasmagoria 316 



ELECTRICITY 319 



Electrical attraction and repulsion 324 



Of the electric spark 328 



Influence of points in electricity 331 



Ley den phial and electric shock » 335 



Electrical battery 340 



Electrophorus 344 



Universal discharger , 315 



