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Designed nearly 150 years ago but never actually built until recently, the Difference Engine No. 2 designed by Charles Babbage (1791 to 1871) is a piece of Victorian technology meant to tussle with logarithms and trigonometry long before the first modern computer. Technophiles have a rare opportunity beginning May 10 to see one of these devices (only two exist) on display at the Computer History Museum in Mountain View, Calif.



Babbage's automatic computing engine consists of 8,000 bronze, cast iron and steel parts, weighs five tons, and measures eleven feet (3.4 meters) long and seven feet (2.1 meters) high. Museum guest curator Doron Swade used Babbage's own plans to bring the engine to life.



Babbage is also credited with inventing the cowcatcher, dynamometer, standard railroad gauge and heliograph ophthalmoscope as well as uniform postal rates, occulting lights for lighthouses and Greenwich time signals.



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