## "A New Type of Differential Analyzer" in Journal of the Franklin Institute 240 pp. 255-326, 1945 WITH "A Continuous Integraph" in Journal of the Franklin Institute 203 pp. 63–84, 1927

Philadelphia: The Franklin Institute. 1st Edition. BOUND, 2 FULL-VOLUME FIRST EDITIONS OF TWO IMPORTANT PAPERS BY VANNEVAR BUSH ON HIS DIFFERENTIAL ANALYZER – A CRITICAL STEP IN THE DEVELOPMENT OF THE MODERN COMPUTER. Bush’s accomplishment evolved in several iterations, each a stunning technological achievement – each a machine that employed mechanical integrators that could be interconnected and reconfigured as desired, each an analog computing machine that, at the time, was the most powerful computing machine prior to the digital computer.

Vannevar Bush (1890–1974) was an electrical engineer at the Massachusetts Institute of Technology. In his own words, ““I was trying to solve some of the problems of electric circuitry….I was thoroughly stuck because I could not solve the tough equations….” (Computer History Portal). Rather than abandon his work for lack of a tool capable of the task, Bush set about inventing one.

The 1927 paper offered here, "A Continuous Integraph" describes Bush’s first generation differential analyzer – then called the Integraph -- a machine that could be used to solve first order differential equations directly and second order by successive approximation. Of the invention, Bush wrote “A mechanical integraph has been developed which plots continuously the integral of the product of two functions. It uses the principle of the electrical integrating watthour-meter combined with a moving table. Errors of the machine have been reduced to an average of 1 per cent. for common uses. By cross-connecting the device in a simple mechanical way, it is possible to solve certain types of integral equations. A link motion has been added which plots the product of two given functions. Various uses have been made of the instrument for solving problems in connection with electrical circuits, continuous beams, etc., and certain problems involving integral equations” (Bush, 1927, p. 63).

BETWEEN 1928 AND 1931, Bush worked to a develop differential analyzer capable of modeling power networks and able to solve specific classes of differential equations. By this time “Bush’s Differential Analyzer filled a room with a complicated array of gears and [cams connected to steel shafts] driven by electric motors. Wheel-and-disc “integrators” at its heart could be connected to 18 long, rotating shafts” (CHP).

In the 1945 Bush paper offered, "A New Type of Differential Analyzer”. The paper describes Bush's third generation differential analyzer, one able to predict the performance of electrical circuits. With 2,000 thermionic valves, the machine was largely electronic and was input by paper tape. Known as the Rockefeller Differential Analyzer (RDA), the analyzer was “financed by the Rockefeller Foundation, this machine used vacuum tubes and relays. The 100 ton RDA was a revolutionary calculating machine; it was immediately classified” (Vannevar Bush and the Limits of Prescience, February 11, 2004). Bush’s invention was a device that saved hundreds and thousands of hours in calculations and would be used to solve problems in atomic physics and many other fields, to say nothing of presaging the electronic digital computer. Item #1116

CONDITION & DETAILS: Philadelphia: The Franklin Institute. Two volumes. Ex-libris with a very small stamp at the foot of each title page and on the verso. 4to (9.5 x 6.5 inches). Vol. 203: [6], 881, [4]. Vol. 240: [6], 512, [4]. Both volumes have been handsomely rebound in marbled paper boards over brown cloth. Gilt-lettered and ruled at the spine, as well as the boards. Pristine inside and out. Both volumes are near fine.

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Price:
$2,000.00
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