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In early July 1608, red drops on walls and stones around Aix-en-Provence were taken as evidence that blood had fallen from the sky. Nicolas-Claude Fabri de Peiresc investigated the stains. The account preserved by his biographer Pierre Gassendi describes direct inspection, an unsuccessful attempt to verify a frightening story, and an accidental observation of a butterfly leaving a red drop inside a box. Peiresc then compared that deposit with the distribution of the outdoor marks.
The distinction between blood-coloured stains and a witnessed fall of blood is central to this case. Gassendi did not simply describe a strange shower and attach a scientific name to it. He set out a sequence in which some details were observed, others were reported, and one dramatic story failed when Peiresc tried to check it. The insect explanation depended on those distinctions.
The source and its distance from 1608
The main source used here is Gassendi’s Life of Peiresc in William Rand’s 1657 English translation, The Mirrour of True Nobility and Gentility. The complete relevant passage appears in BookII, under 1608, on printed pages 123–125. The original scan makes the year clear even where automated text recognition misreads individual figures. The English publication date is not the date of the reported phenomenon.
Gassendi was Peiresc’s biographer, not a laboratory analyst writing a modern case report. His account is retrospective and admiring. It remains an important early source for what Peiresc was said to have inspected and concluded, but its narrative should not be converted into a surviving 1608 field notebook or a set of independently preserved specimens. The review here concerns the passage itself, not a claim to have examined every letter or manuscript associated with Peiresc.
Gassendi described stains within Aix and around nearby settlements, including city walls and the walls of a churchyard near the city boundary. This establishes an area of reports, without identifying every marked building today. The visible material consisted of drops or spots on surfaces. Calling them rain already introduced an interpretation of how they had arrived there.
A story checked rather than repeated
Peiresc went to inspect the coloured stones. He also tried to speak with agricultural workers beyond Lambesc who were reportedly so alarmed by falling blood that they abandoned their work and fled into buildings. According to Gassendi, this story about the workers proved unfounded. The stains were not dismissed along with the failed story; they remained something to examine.
This separation is one of the account’s strongest features. A dramatic report can contain a real observation and an unsupported explanation at the same time. The failure of the fleeing-workers story does not show that no red material existed. Equally, the existence of red marks cannot be used to validate a supposed eyewitness scene that the investigator could not substantiate.
Several competing interpretations circulated. Some naturalists attributed the appearance to vapour drawn from red earth and subsequently falling as coloured liquid. Peiresc objected that evaporation did not carry colour in that fashion, using the example of transparent distilled water from red roses. Other people invoked witches or devils. Gassendi presents Peiresc as rejecting that claim as conjecture, rather than treating fear as evidence of a supernatural agent.
The butterfly in the box
Some months earlier, Peiresc had enclosed an unusual insect in a box and then forgotten it. Hearing movement, he opened the container and found that a butterfly had emerged. It flew away, leaving a conspicuous red drop on the bottom. Rand’s translation compares its breadth to a coin. That is a visual description, not a measured volume or an analysis showing human blood.
The timing supplied another link. The emergence occurred around the beginning of the same month in which unusually numerous butterflies were being noticed outdoors. Peiresc proposed that butterflies resting on walls could have left similar deposits. His box observation provided a material process capable of producing a blood-like spot without blood falling from clouds.
The Children’s Butterfly Site explains that red liquid expelled after emergence is metabolic waste left over from metamorphosis. That biological fact helps explain why the historical observation is plausible. It does not identify a particular 1608 butterfly specimen or provide a modern test of a stain that no longer survives. The contemporary biological explanation and the historical attribution are related questions, rather than interchangeable evidence.
Testing where the stains occurred
Peiresc returned to the outdoor marks and examined their position. Gassendi says they were not on exposed rooftops or on the projecting upper surfaces where falling liquid would be expected. Instead, they occurred in cavities and recesses where small insects could shelter. The affected walls bordered fields, and the spots were at moderate heights rather than on the highest parts of the buildings.
These details supplied a comparison between two proposed causes. A deposit arriving from above and one produced by insects resting on sheltered surfaces predict different distributions. The significance was therefore not simply that both the box and the walls looked red. The position of the marks reportedly agreed with the insect interpretation and conflicted with the simple falling-shower account.
The passage ends with another inspection after Peiresc discussed his reasoning before a group. Participants went through the countryside and found drops on rocks and stones, again on sheltered or lower surfaces rather than those most exposed to the sky. Gassendi thus records an attempt to check the pattern with others present. It is a narrative of corroboration, although it does not preserve separate signed observations from each participant.
Later certainty and the limits of the case
The story subsequently entered works on insects and popular explanations of marvels. Frank Cowan’s 1865 Curious Facts in the History of Insects reproduces an extended Gassendi passage and treats the insect cause with confidence. It also offers possible butterfly species. That later identification should not be confused with a specimen determination made by Peiresc. The reviewed 1657 passage describes a beautiful butterfly without a modern species name.
Nor should Peiresc’s reasoning about Aix automatically settle every earlier report of blood rain. Gassendi says he extended the same explanation to accounts associated with Gregory of Tours and other historical periods. Those comparisons are part of his reasoning, but they are not direct observations of those separate events. This page concerns Aix’s 1608 surface-stain reports, rather than combining centuries of differently sourced phenomena into one supposedly demonstrated cause.
The appropriate assessment is possibly explained. The account documents a real source of red insect fluid and a substantial observational comparison supporting its application to the outdoor stains. The association of every reported spot with that cause remains a historical inference conveyed through a later biography. No retained sample, chemical identification or complete independent record of the reported distribution has been examined here. Those limits do not provide positive evidence for literal blood rain or a supernatural origin.
Illustration and location
The lead image is a much later illustration published in Louis Figuier’s Les Insectes in 1875. Its theatrical scene belongs to the story’s later presentation. It is not a 1608 eyewitness drawing, a portrait identification of the people supposedly present or a record of the exact places Peiresc examined. Its publication and public-domain source are credited separately from the incident account.
The map uses a broad Aix-en-Provence reference at 43.528,5.446, rounded from sourced city coordinates. It is not a surviving stained wall, a churchyard corner or the position of Peiresc’s box. The account ranges through the town’s margins and surrounding countryside, and the precise distribution cannot be recovered from a single point. The pin locates the historical reporting area while preserving that uncertainty.
Sources and further reading
Original 1657 public-domain edition PDF, Wellcome Library copy
Children’s Butterfly Site: red material after emergence is metabolic waste
Figuier, Les Insectes (1875): later illustration, exact file and public-domain rights
Aix-en-Provence town coordinates: approximate case area reference