The Philosophical Breakfast Club (39 page)

In a sense, the charge was accurate. For Babbage, the enemy of the good was always the better. Once he had begun devising the Analytical Engine, he lost interest in continuing work on the Difference Engine. And by this point the government was ready to call it quits as well. The final word cutting off all funding for Babbage’s engine would not come until 1842. Meanwhile, Babbage kept working on the plans of his more powerful computer. In December 1838, Babbage resigned from the Lucasian professorship, so that he could spend all his time on his new invention, and avoid making any trips to Cambridge, where he was bound to run into Whewell.

T
HE ARGUMENT
between Whewell and Babbage over what may seem to us an esoteric point in natural theology turned out to have revolutionary consequences. Babbage devised his demonstration with the feedback mechanism on the Difference Engine to show how wrong Whewell was
about the need for God’s intervention in the natural world, which led Babbage to present God as a computer programmer—in turn spurring him to invent the world’s first programmable computer. But this was not the only consequence of this dispute.

When he attended his first Dorset Street soirée, Darwin had returned to England after his voyage on the
Beagle
only months before. He was making up for lost time socially and intellectually. At Babbage’s parties, and at more-intimate gatherings at his brother Erasmus’s house, Darwin was meeting the cream of what would now be called England’s “chattering classes”: journalists, political thinkers, scientists. Darwin began to read and discuss the latest theories of science and society, just as he was mulling over his observations of flora and fauna during the long voyage around the world, some of which led him to begin to wonder whether the accepted view of the fixity of species was correct.

According to this view, species were created one at a time by God, and they entered existence with all the same characteristics that they had for the rest of time. No one could now deny that some species became extinct, but that was the only type of species change accepted by most men of science. While traveling around the world, however, Darwin had made three observations that called this view into question. He had realized that the same place was sometimes home to fossil species and living species that were very similar but not the same—for example, the extinct megatherium and the living armadillo. This suggested that possibly there was, indeed, change in species over time, that perhaps the megatherium was an ancestor of the armadillo. He had also seen, in the vast expanse of the pampas, where there were no topographical boundaries (for example, mountains or large bodies of water), that one species would have its own area, and that area would grade into the area of a different but related species, such as two different kinds of rheas, or ostriches. This seemed evidence that species changed over space as well as time—the same land with the same characteristics could be home to different but related species. Further, in the Galápagos Islands, Darwin realized that the typical reasoning, which said that places with similar climates and habitats should be home to the same species, was not true. The Galápagos Islands and the Cape Verde Islands were quite similar, yet they were home to different kinds of species. Even more provocative was the fact that the species of the Galápagos resembled those in South America, and the species on the Cape Verde Islands resembled those of continental Africa—so the species
in each place seemed to have been determined by geographical proximity rather than by climate and other local conditions.

Although Darwin thus had begun to wonder about the species question while aboard the
Beagle
, he did not seriously begin to consider the possibility of evolution until after he returned to England. Sometime in the second half of March 1837, Darwin made the first clearly evolutionary comment in an undated entry in his notebook, voicing the possibility that “one species does change into another.”
⁸⁹
This was shortly after John Gould, who had been studying Darwin’s bird specimens from the Galápagos, told Darwin that each island seemed to have its own species of mockingbird—a very telling detail, as it suggested that a species might branch off and develop differently when geographically separated from its related species. But the mid-to-late-March dating of this comment is significant for another reason: it was soon after Darwin attended his first soirée at Babbage’s house, in early March, after his visit to Cambridge.

So at the very same moment he was introduced to Babbage and his machine, Darwin was questioning the fixity of species and the prevalent notion of special creation. Sitting in the drawing room of Babbage’s house, witnessing his display with the demonstration model of the Difference Engine, and hearing Babbage propose the view that God did not need to intervene each time in order to bring about new species—because God could have preset the lawful change into His Creation at the beginning of time—Darwin must have been struck by how Babbage’s notion of a divine programmer could explain the observations he had made on the
Beagle
. There is no historians’ “smoking gun” here; Darwin did not record in his notebook, “Babbage gave me this idea.” Neither, for that matter, did he record that “I have this idea because of Gould’s mockingbird results.” The exact impetus behind the idea has remained a mystery. Darwin certainly could have come up with the notion of transmutation of species by a natural process even without witnessing Babbage’s demonstration. But it is clear that Darwin would have seen how Babbage’s view of a divine programmer gave him a way to reconcile his belief in God with his growing sense that new species arose from old ones in a purely natural, evolutionary process.

Around July of that year, Darwin first sketched his iconic branching of a single evolutionary tree, from which all existing species arose. In September of 1838—a few weeks after seeing Richard Jones, who probably recommended the book to him
⁹⁰
—Darwin read Malthus’s
Essay on the
Principle of Population
, and realized with a spark of insight that the inevitable “struggle for existence” described by Malthus could drive a theory of evolution by natural selection: in a situation where individuals have to struggle for their share of paltry resources, those with variations, however slight, which give them an advantage in getting those resources would tend to live longer, and have more offspring, than individuals without this variation. Over time this process would lead to the formation of a new species, all of whose members had the favorable characteristic.

In December 1838, Darwin read Babbage’s
Ninth Bridgewater Treatise
, and saw there the reprinted letter from Herschel to Lyell. “Herschel calls the appearance of new species, the mystery of mysteries and has a grand passage on the problem. Hurrah!” he excitedly recorded in his notebook.
⁹¹
Even the “great man” himself, he saw, allowed the possibility of “natural causes” acting on species to create new ones. (Darwin would use the phrase “mystery of mysteries,” along with a reference to “the greatest living natural philosopher,” in the opening line of the
Origin of Species.
) By this point, Darwin realized he now had a theory “by which to work,” and went on compiling evidence and refining it for the next twenty years.

The origin of Darwin’s theory of evolution can be traced back not only to the voyage of the
Beagle
, but also to Babbage’s Dorset Street drawing room. As he sat in Babbage’s drawing room, Darwin began to think about God as being very much like a computer programmer, presetting his originally created organisms with variations that would arise thousands or even millions of years later, causing new species to arise from the old. This thinking would lead Darwin in the coming years to his breathtakingly radical theory of evolution, which some—including Darwin himself—would come to think did away with the need for any divine programmer at all.

T
HIRTY-THREE YEARS AFTER THE FACT
, M
ARGARET
H
ERSCHEL
still recalled with photographic clarity the visit a friend of her husband’s had paid to Slough. On February 1, 1839, William Henry Fox Talbot took the new railway from London to visit John, bringing with him specimens of an ingenious method he had devised to capture images on paper. Margaret recalled that Talbot had shown the two of them “his beautiful little pictures of ferns and Laces taken by his new process.” He had produced them by placing leaves and pieces of lace on top of specially treated paper inside a wooden box covered with a glass lens, and setting the whole apparatus outside on the lawn of his estate, Lacock Abbey. The action of the sun on the light-sensitive silver chloride coating on the paper turned the areas around the objects a warm, dark brown, while the parts covered up by the leaves and lace were left a bright white—not unlike the effect of the potter Josiah Wedgwood’s jasperware, with its creamy white designs against darker backgrounds.

The problem, Talbot complained to the Herschels, was that over time the continued exposure to light would cause the images of the leaves and laces to turn a dark brown, just like the background, and the picture would be lost. He had no way to “fix” the images. Margaret remembered that her husband had said, “Let me have this one for a few minutes.” After a short time he returned, and handed the picture to Talbot, saying, “I believe that you will find that fixed”—and thus, Margaret proudly boasted, the problem of rendering photographs permanent was solved by her husband.
¹

Herschel had, in this telling of the story, realized with a flash that experiments he had conducted in 1819 could provide the solution. He had then discovered a seemingly trivial property of hyposulphite of soda—that
it put silver salts into a water-soluble form, so that they could be washed out with water. Talbot’s treated paper was made with a light-sensitive silver chloride. The images were formed by the action of light on the silver compounds that had been spread on the paper’s surface. Where the light acted, the compounds were reduced to a deposit of pure silver, while the areas hidden by the object placed on top of the paper remained in their compound state, which meant they were still light-sensitive. What was needed was a way to either neutralize or remove the silver compounds, while leaving alone the metallic silver. Herschel knew that once the silver salts on the treated paper were washed out, no further action of light could darken the images. Herschel had invented the “hypo” still used in photographic development today (though the chemical name of hyposulphite of soda has been changed to sodium thiosulfate, it is still referred to by photographers working with film as “hypo”).

Margaret’s memories are slightly off; in fact her husband had ripped the picture in half, treating one piece in the hyposulphite of soda solution and leaving one piece untreated. Both halves still exist today, affixed to a page in Herschel’s experimental notebooks. The treated half still shows, very faintly, the image of a plant stem, while the untreated part is completely darkened, and the notebook has retained the tart, vinegary odor of the chemical.
²

What Margaret did not know, or remember, was that Talbot had written to her husband several days before arriving, describing his images but not giving any details of his process for creating them. The day before Talbot arrived in Slough, Herschel had prepared silver-nitrate paper, placed it in a boxlike wooden camera, aimed it at his father’s forty-foot telescope, and then fixed the image with the hypo. Although this tale is less dramatic, perhaps, than Margaret’s version, it is no less striking: within a day or two of hearing about Talbot’s marvelous results, Herschel had grasped all the essentials of the process required to make light-sensitive paper, direct upon it an image, and fix the image with his hypo; in only a few hours Herschel had re-created—and gone beyond—what had taken Talbot months to accomplish.
³

Herschel and Talbot had met in the summer of 1824. After a holiday in France and Italy, Herschel made an expedition to the Tyrol Mountains to search for minerals for his chemical experiments. He then went on to Munich, to meet with the optical-glass maker (and discoverer of the black lines in the solar spectrum named after him) Joseph von Fraunhofer.
Fraunhofer presented Herschel with a large prism of flint glass, which Herschel used twenty years later in key experiments in photochemistry. While in Munich, Herschel met Talbot and his family.

Talbot was born in 1800 in Dorset, on the southwest coast of England. As a young boy, he spent many happy hours at Bowood, the country home of his aunt Louisa and her husband, the second Marquis of Lansdowne, in Wiltshire. A generation earlier, the first Marquis of Lansdowne had employed Joseph Priestley as a librarian and “literary companion”; it was in his laboratory at Bowood that Priestley discovered his “dephlogisticated air” (that is, oxygen) in 1774.
⁴
After graduating in 1821 from Trinity College, Cambridge, where Whewell was his tutor, Talbot set up a chemical laboratory of his own. Once he met Herschel, the two men began to correspond about their chemical results.

Although he always gave Talbot credit for the discovery of photography, Herschel was the one who first published the chemical results leading to the new technology. Not only did he publish the paper on the hyposulphites in 1819, but, in his 1827
Encyclopaedia Metropolitana
article on “Light,” Herschel had hit on the main principle of Talbot’s photographic process, not developed by Talbot until years later: “It has long been a matter of everyday observation,” Herschel noted, “that solar light exercises a peculiar influence in altering the colors of bodies exposed to it … especially those of silver [which are] speedily blackened and reduced when freely exposed to direct sunshine.”
⁵
In 1831 Herschel had even demonstrated the ability of platinum salts to form a simple image under the influence of light.