262 PROGRESS OF SCIENCE. 



lines from their true spectroscopic position, and thereby 

 corroborates the beautiful exactness of the spectroscopic 

 revelations (due to the working of Doppler's principle) 

 as regards the speed and direction of stars' motions. But 

 more wonderful than all this, it detects and shows us 

 stellar and nebular systems existing far beyond the reach 

 of telescopic and spectroscopic power, thereby opening new 

 regions of astronomical knowledge in a way wholly undreamt- 

 of by Newton or Laplace. 



1771 1834. Senefelder invented LITHOGRAPHY, which 

 has proved so useful to industry and the propagation of 

 artistic works. 



1791 1872. Morse invented the TELEGRAPHIC APPA- 

 RATUS which bears his name and has been all but universally 

 adopted. 



18031859. Stephenson (Robert) by his gigantic con- 

 struction of the BRITANNIA TUBULAR BRIDGE across the 

 Menai Straits (1850), and the Victoria tubular bridge across 

 the St. Lawrence, near Montreal, proved engineering to be 

 capable of overcoming every mechanical problem ; a fact 

 of which living engineers have afforded us numerous evi- 

 dences by their colossal structures witness the Eiffel Tower 

 and the Tay Bridge. 



18031887. Whitworth (Sir Joseph) invented a whole 

 set of MACHINE-TOOLS that have revolutionised the labour 

 of our workshops, and thereby was one of those who 

 ushered in the Age of Steel. Before him the rule of 

 thumb was pretty universal. Whitworth introduced ACCU- 

 RACY of machine-tools. Such a thing as a true lathe did 

 not exist before him. We owe to him a measuring machine 

 to the 2OO,oooth part of an inch, so true, that if a rod of 

 iron is laid upon it and the hand holding it is not removed, 

 the expansion of the rod by the heat of the hand will be 

 at once indicated. Whitworth also introduced a UNIVERSAL 

 THREAD in screws an improvement which every one can 

 appreciate. 



18081890. Nasmyth (James) invented the steam 

 hammer, without which the modern steel industry could 

 never have been carried out (1842). 



