442 A SHORT HISTORY OF SCIENCE 



India, the fibres being separated from the seeds by a rude hand ma- 

 chine known as a churka, used by the Chinese and Hindus. By 

 this it was impossible to clean cotton rapidly. The invention there- 

 fore in 1793 by Eli Whitney of Connecticut of the saw cotton- 

 gin which enormously facilitated this separation was one of the 

 most important inventions ever made. This consisted in a series 

 of saws revolving between the interstices of an iron bed upon which 

 the cotton was so placed as to be drawn through while the seeds were 

 left behind. The value of the saw gin was instantly recognized and 

 the output of cotton in America was rapidly and immensely increased 

 by its use. 



STEAM TRANSPORTATION. Boats and ships propelled by man 

 power or by the wind have been used from time immemorial, and 

 parallel rails for wheeled conveyors moved by animal power or by 

 gravity preceded the steam locomotive. The steamboat and the 

 steam vehicle appeared at (or in the case of the latter even before) 

 the opening of the nineteenth century. 



The first practically successful steamboat was a tug, the Charlotte 

 Dundas, built and operated in Soctland for the towing of canal boats 

 by Symmington in 1802. The first commercially successful steam- 

 boat was Fulton's Clermont, on the Hudson, in 1807. The first 

 steam-engine to run on roads appears to have been Cugnot's in France 

 in 1769. The first to run on rails was Trevithick's, in 1804, built to 

 fit the rails of a horse railway. This engine also discharged its exhaust 

 steam into the funnel to aid the draught of the furnace, a device 

 of fundamental importance to the further development of the loco- 

 motive. The first practically successful locomotive was Stephenson's 

 Rocket (1829). 



The compound (double or triple expansion) engine, which dates 

 from 1781 (Hornblower), 1804 (Woolf), and 1845 (McNaughton), 

 embodies what is perhaps the greatest single improvement in the 

 steam-engine in the nineteenth century. The turbine has begun to 

 replace the reciprocating engine only very recently (1900). 



THE ACHROMATIC COMPOUND MICROSCOPE. The compound 

 microscope, after its introduction about the middle of the seventeenth 

 century, and its use by Malphigi, Kircher, Leeuwenhoek, Grew, and 

 others, was of only limited value because of the spherical, and espe- 

 cially the chromatic, aberration of its lenses. This remained true 

 until long after Huygens had perfected the eye-piece of the telescope, 



