On 16 October 1869, on William C. “Stub” Newell’s farm at Cardiff, in the Onondaga Valley of central New York, two hired men digging a well struck a vast stone figure that looked like a petrified human ten feet tall. Word spread within hours, and a tent went up over the pit. It was a fraud from the first stroke. The figure was a block of gypsum, quarried in Iowa and carved in Chicago at the direction of George Hull, a Binghamton tobacconist and avowed skeptic, who had buried it on his cousin Newell’s land roughly eleven months earlier and waited for it to be “found.”
The deception barely outlived its own celebrity. Within weeks geologists pronounced the object impossible, and on 10 December 1869 — under two months after the discovery — Hull confessed the whole scheme to the press, having already pocketed the money. Yale’s pioneering paleontologist Othniel Charles Marsh examined the giant and dismissed it as “of very recent origin, and a most decided humbug,” noting fresh tool marks and a polished surface that water-soluble gypsum could never have kept underground. The courts followed: in February 1870 the giant and a copied rival were both declared fakes.
Hull’s motive was not, at first, money. By his own account he conceived the hoax after a theological argument with a revivalist preacher who insisted, citing Genesis 6:4 — “there were giants in the earth in those days” — that scripture was literally true. Hull set out to manufacture exactly the relic such literalism predicted, then watch the credulous pay to believe it. He spent a reported 2,600 dollars building the giant and recouped a fortune; a syndicate led by the Syracuse banker David Hannum bought a three-quarter interest for a sum reported around 30,000 dollars, and the showman P.T. Barnum, refused the original, simply commissioned a plaster copy and exhibited it as the genuine article.
The Cardiff Giant endures less as a mystery than as a parable. It fooled no expert who was allowed to test it, yet it drew enormous crowds because it confirmed what many wished to be true and arrived wrapped in the authority of the soil. The phrase “there’s a sucker born every minute,” long misattributed to Barnum, is most plausibly traced to Hannum, exasperated that the public was paying to see Barnum’s fake of Hull’s fake. Today the original rests at the Farmers’ Museum in Cooperstown, New York.
In 1903, at the University of Nancy in eastern France, the respected physicist Prosper-René Blondlot announced that he had discovered a new species of radiation, which he named N-rays after his city. There was no such radiation. N-rays were not a forgery planted by a swindler but an illusion sustained by sincere observers, including Blondlot himself, who convinced themselves that a faint phosphorescent screen glowed a little brighter when invisible rays fell on it. The “discovery” stood for barely a year before the American physicist Robert W. Wood exposed it in 1904 by secretly removing the essential aluminium prism from Blondlot’s apparatus in a darkened laboratory; Blondlot and his assistant went on reporting the rays they could no longer possibly have been seeing.
What makes the case a landmark is how much real science it briefly recruited. After Blondlot’s first papers, roughly 120 other scientists, mostly French, published an estimated 300 articles describing N-rays emanating from metals, magnets, chemicals, the human nervous system, and almost any object one cared to test. Blondlot himself published more than two dozen. The French Academy of Sciences moved in 1904 to award him its prestigious Leconte Prize. For a season, an entire research community measured, refracted, and tabulated something that did not exist.
The exposure was swift and clinical. The British journal Nature sent Wood — already known as a debunker of dubious claims — to Nancy to see the experiments for himself. In a sequence of demonstrations conducted, as the method required, in near-total darkness, Wood quietly pocketed the aluminium prism that supposedly split the rays into a spectrum, and on another occasion swapped an inert piece of wood for a steel file said to emit them. The observers reported no change. Wood’s letter, sent on 22 September 1904 and published in Nature on 29 September 1904, concluded that the experimenters had “in some way deluded” themselves. Within months, belief in N-rays collapsed everywhere outside Nancy.
The damage was to credibility rather than to lives. No patient was harmed, no fortune stolen; what was lost was the reputation of a serious physicist and, briefly, the authority of French experimental science. Blondlot, who had done genuine work earlier in his career, retired in 1910 and is said to have remained convinced of the rays for years; he died in 1930. The episode became a permanent teaching case, later christened “pathological science” by the chemist Irving Langmuir — the study of how honest researchers fool themselves at the threshold of perception.
On 31 March 1848, in a small rented farmhouse in Hydesville, New York, two sisters — eleven-year-old Kate Fox and her fourteen-year-old sister Margaret, called Maggie — began producing mysterious raps that seemed to answer questions, claiming an unseen presence was knocking back. There was no presence. Forty years later, on 21 October 1888, before a paying audience of some two thousand at the New York Academy of Music, Margaret Fox stood up and confessed: the raps had always been a trick, made by snapping the joints of her toes and ankles, a habit the girls had begun as a prank on their mother and never stopped. She demonstrated the sound on stage, her bare foot on a small wooden stool, while doctors on the platform confirmed the noise came from her toes.
Between those two dates the Fox sisters had founded modern Spiritualism, one of the largest religious movements of the nineteenth century. What began as two children fooling a credulous adult grew, under the management of their much older sister Leah, into a national sensation: public demonstrations, paid séances, and a doctrine that the living could converse with the dead through rapping mediums. The movement spread through the United States and Europe and, by the 1880s, was credited by its own adherents with millions of believers, swelled enormously by the grief of the American Civil War, which left countless families desperate to reach the sons they had lost.
The confession was as public as the hoax had been, and it was bought. The New York World reportedly paid Margaret around 1,500 dollars for the exclusive, and she denounced Spiritualism from the stage as a fraud she had helped create. Yet the recantation did not stick. Within roughly a year, impoverished and pressured, Margaret took her confession back, and many Spiritualists simply refused to believe she had ever told the truth. Both sisters died soon after in poverty and ill health — Kate in 1892, Margaret in 1893 — and the movement they had launched carried on without them.
The Fox case is a defining specimen hoax not because the trick was clever but because it was so trivial and yet scaled so far. Two girls cracking their toes produced a phenomenon that drew in judges, editors, scientists, and a future Sherlock Holmes author, and that hardened into a faith resilient enough to survive its own founder’s confession. The mechanism of the deception was a parlour prank; the mechanism of the credulity was grief, showmanship, and the human refusal to let the dead stay silent.
In Berlin around the turn of the twentieth century, a horse named Clever Hans appeared to do arithmetic, tell time, read, and spell, answering questions by tapping out numbers with his hoof. He could do none of those things. In 1907 the psychologist Oskar Pfungst demonstrated that Hans was not calculating at all but reading tiny, involuntary movements in the body and face of whoever asked the question — cues that told the horse when to start tapping and, decisively, when to stop. The arithmetic lived in the questioner, not the horse. The case is unusual among hoaxes because there was no hoaxer: the owner, Wilhelm von Osten, sincerely believed in his horse’s intellect and was himself among those deceived.
That sincerity is central to the file. Von Osten, a retired Berlin schoolteacher with an interest in animal intelligence, had spent years patiently “teaching” Hans, an Orlov Trotter stallion, using number boards and drills. He charged no admission, sought no fraud, and submitted the horse freely to investigation. In 1904 an official commission of thirteen — assembled under the philosopher and psychologist Carl Stumpf and including a veterinarian, a circus trainer, schoolteachers, and the director of the Berlin zoo — examined Hans and concluded there was no trickery. They were right that von Osten was honest and wrong about what the horse was doing.
The decisive work came from one of Stumpf’s young associates, Oskar Pfungst, who treated the horse not as a wonder to be admired but as a problem to be controlled. Through a careful series of tests published in 1907, Pfungst varied two things the commission had not properly isolated: whether the questioner knew the answer, and whether Hans could see the questioner. The results were stark. When the questioner knew the answer and was visible, Hans was right the great majority of the time; when the questioner did not know the answer, or when Hans could not see them, his accuracy collapsed. Hans was reading people, and could only “know” what his human knew.
Pfungst then identified the mechanism precisely: as the hoof-taps approached the correct count, the questioner unconsciously increased in tension and made a minute postural or facial change, releasing it at the right number, which the horse had learned to use as a signal to stop. The effect was so reliable that Pfungst could make Hans stop on any number by performing the cue deliberately — and found he could not suppress the cue in himself even when he tried. From this came the enduring term “the Clever Hans effect,” now a foundational warning in every science that studies behaviour: the danger of an experimenter unconsciously cueing the result they expect.