Charles Babbage’s son Henry Prevost Babbage completed and published his father’s unfinished edition of writings on the Difference Engine No. 1 and the Analytical Engine, together with a listing of his father’s unpublished plans and notebooks. These appear under the title of Babbage’s Calculating Engines.
This work was the principal source of information for the technical operation of Babbage’s Difference and Analytical engines. Toward the end of his life, Babbage began assembling his own and other’s previously published writings on his Difference and Analytical Engines with the intent of publishing a history of his work designing the machines, and descriptions of the way that the machines would operate. However, Babbage died before he could accomplish this task. He had the first 294 pages of this work typeset and printed on slightly varying qualities of paper during his lifetime. The differences in the paper used for portions of the work would suggest that sections were printed intermittently rather than all at one time. It would appear that Babbage’s purpose in producing this work was to collect the most significant published writings on his calculating engines, most of which had appeared as obscure pamphlets or in little-read journals, together with a listing of what remained unpublished, including all of Babbage’s notebooks and engineering drawings (listed on pp. 271-294), in the hope that his unfinished projects might be completed at some future date.
Almost twenty years after Babbage’s death, his youngest son, Major-General Henry Prevost Babbage, to whom Babbage had bequeathed his parts for his calculating engines, and everything else pertaining to them, completed the book, incorporating the printed sheets that Babbage had produced along with concluding material, reflecting his own frustrated efforts to effect realization of Babbage’s engines. Were it not for this volume, and for the bibliography of Babbage’s works published both here (on the last three printed pages of the book) and in Babbage’s autobiography, Babbage’s achievements might have been forgotten. Henry Babbage also completed six small demonstration pieces of the Difference Engine No. 1, and in 1910 at the age of 86, Henry Babbage also completed an experimental four-function calculator for the Mill for the Analytical Engine. This was the only portion of the Analytical Engine that was ever produced in metal.
As it turned out Babbage’s designs were not implemented until the 20th century because in the era of human computers there was no pressing need for the machines that Babbage envisioned and designed. Yet because of these published works, Babbage’s ambitions and his ideas remained alive in the minds of people working in mechanical computation long after his technology had fallen into obsolescence. When Vannevar Bush suggested in 1936 that electromechanical technology might be the way to realize “Babbage’s large conception” of the Analytical Engine, he cited this volume among his references; and in building the electromechanical Harvard Mark I, Howard Aiken saw himself fulfilling Babbage’s ambition. However, some experts have inferred that Aiken’s knowledge of Babbage’s work may have been limited to what he read in Babbage’s autobiography, Passages from the Life of a Philosopher, as Aiken did not include conditional branching in the design of the Mark I—a key idea that Babbage designed into the Analytical Engine.
Hyman, Charles Babbage, Pioneer of the Computer, 254. Van Sinderen, Alfred W. "The Printed Papers of Charles Babbage" Annals of the History of Computing, 2 (April 1980) :169-185 mentions in item CB80, that Babbage listed a History of the Analytical Engine as being “in the press” in 1864.