In January 1885, Henry Slade brought his claimed spirit-writing abilities to Philadelphia for a series of sittings with the University of Pennsylvania’s Seybert Commission. Messages appeared on slates, pencils jumped and an accordion sounded beneath a table. The investigators also reported seeing prepared writing, substitutions and physical movements that accounted for the effects. Their detailed record makes this a case of observed methods, alongside a surviving statement of Slade’s own position.
A commission invited to investigate
Henry Seybert’s gift to the university had included a request to investigate philosophical and religious systems, particularly modern Spiritualism. The resulting commission included physicians, scholars and the engineer Coleman Sellers. William Pepper was its chairman by virtue of being university provost; Horace Howard Furness acted as chairman and George S. Fullerton as secretary. The commission’s 1887 Preliminary Report combines an overview with dated records, retrospective discussion and correspondence. Those layers sometimes describe an episode differently.
The investigators said they would base their conclusions on observations they could personally answer for. Their published account is consequently a primary record of their investigation, rather than a neutral transcript of every event in Slade’s career. Its strongly sceptical language should be distinguished from its concrete descriptions. The Philadelphia experiments were separate from the London sittings and prosecution of 1876, and from the German experiments associated with Johann Karl Friedrich Zöllner.
The first sittings at the Girard House
The dated record begins on 21 January 1885 in Room 24 of Philadelphia’s Girard House. Slade sat at an ordinary table and held a slate below its edge. Scratching was heard; the slate came back with a message attributed to James Clark. Sellers noted that this longer message looked like ordinary flowing handwriting, whereas shorter answers at other stages appeared cramped and written with a flattened pencil point.
Sellers also examined the furniture. Slots beneath the table leaf could hold a slate without a hand supporting it, and he demonstrated that possibility himself. This was a proposed practical opportunity, rather than proof that every message had used the slot. At a later sitting a different, larger table appeared. Slade drew attention to its lack of such slots; paper had been inserted into gaps between its leaves. He supplied a spirit-related explanation for the arrangement, while the investigators thought it obstructed their view.
On 22 January, Fullerton held a slate beneath the table as requested, but no writing appeared on it. Slade’s own slate produced short answers. An accordion played while largely concealed from view, and a pencil was thrown upward from a slate. Fullerton carefully recorded what he could and could not observe: he could occasionally see a corner of the instrument, but could not follow the whole performance. Those qualifications matter more than a later summary suggesting that everything happened in full view.
Watching the slates change
The record for 23 January describes a lengthy message attributed to William Clark. The investigators thought its appearance differed from the short answers. More significantly, Sellers said he had tracked the slates using private marks and established that the displayed slate was not the one represented as having been taken from the table. The minutes describe another slate kept within reach behind Slade’s chair.
The discussion preserves a useful correction. Sellers initially spoke as though Furness had directly witnessed the same substitution. Furness clarified that his knowledge of that particular exchange was inferential, although he distinctly saw Slade grasp an unused slate at another point. The report therefore supports a finding that substitutions were observed, while also warning against turning every observer into an eyewitness to every movement.
Other tests addressed apparently intelligent replies. A deliberately awkward question produced answers the investigators regarded as failing to understand its meaning. They reported Slade glancing at the slate. A complex question receiving a poor answer would not independently demonstrate deception, but in their account it accompanied observations of how questions could be read and replies written. The report’s opening assessment explicitly says the commissioners watched the handling sequence used for short responses.
A message with a newspaper counterpart
At the 24 January sitting, a long communication purportedly from John Tiers announced reunion with his wife, Ann Louisa. Sellers reported that Furness had noticed a newspaper death announcement containing the relevant family information. The commission treated the announcement as a readily available source for the message, rather than evidence that private knowledge had arrived from a deceased person.
The long message also appeared on a slate the investigators said had been substituted. Joseph Leidy distinguished its extensive, regular writing from the brief scrawls produced in answer to questions. This combination was more specific than a general claim that a medium might research his clients: the report identifies a message, an accessible information source and disputed handling of the object carrying it. UKPX has read the commission’s description; the newspaper announcement itself has not been independently recovered for this file.
That sitting included another broken slate. Leidy said he saw Slade knock it against his knee while bringing it out, crushing it into pieces. The accordion provides a further example of the difference between a suggested mechanism and direct observation. Leidy proposed a possible support arrangement; Sellers said the small instrument’s handling could be followed closely. When Sellers looked under the table at Slade’s invitation, the music stopped and did not resume while he watched.
A failed sitting and prepared writing
On 26 January, according to Sellers’s minutes, the performance produced no writing or raps. Slade moved between two slates, declined an immediate request to let Sellers inspect one, and eventually washed its surfaces. Furness said he had seen writing on its face. Fullerton added a separate recollection of Slade accidentally exposing an already written slate and identifying it as the wrong one.
The commission also asked about using closed double slates. Slade said that the spirits had forbidden sealed slates because tricks had been played upon them. Even an offer to open and show the slates first did not resolve that objection. These refusals do not by themselves prove a physical method, but they explain why the investigators did not regard the sittings as independently controlled tests of sealed writing.
The detailed narrative calls 27 January the last sitting, although an introductory description of the series extends its range to 28 January. Pepper’s separate memorandum places his 27 January encounter at Furness’s Philadelphia home. It would therefore be misleading to place every recorded experiment in the hotel room or claim an additional fully documented sitting on the 28th. During the final observations, covered slates were displaced and revealed substantial writing the investigators believed had been prepared for use.
Pepper reported directly seeing Slade kick his chair while drawing attention to slate-scratching sounds. Other movements beneath the table were described more cautiously as consistent with making raps. Two compasses showed no change beyond motion attributed to the table being shaken. The record does not establish an anomalous magnetic effect.
Slade’s reply and the finding
A letter from Furness dated 26 January asked Slade to confirm that the committee had to accept the conditions he attributed to spirits. In his reply of 4 February, Slade expressed approval of the committee’s treatment, maintained that he was a channel for unseen intelligences and confirmed that their conditions had to be accepted. He regarded the results as preliminary to possible further experiments. His response did not concede the investigators’ account of deception.
On 6 February, the commission unanimously adopted a resolution accepting the Philadelphia reports as consistent with the observations of those members present. The published overview concluded that the manifestations it had observed with Slade were fraudulent. Its strongest support lies in reported direct sightings of substitutions, prepared writing and ordinary bodily actions. Some individual mechanisms remained suggestions, and those should not be presented as if filmed or experimentally reconstructed in every instance.
Outcome: Closed (Explained). The commission documented observed physical methods and prepared or substituted slates in this Philadelphia series. This classification concerns those investigated performances; it does not claim to settle every experience ever reported with Slade, the separate London controversy or all Spiritualist beliefs. Slade continued to interpret the sittings through spirit agency, but the original report supplies affirmative observations of ordinary causes rather than relying solely on disbelief or an absence of results.
Location and access
Location note: The map uses a rounded Philadelphia city reference from the U.S. Census Gazetteer. It is an approximate city pin, not the former hotel room, a private residence or an invitation to enter a property. No present-day visitor venue is verified for this historical investigation.
Sources and related reading
Seybert Commission, Preliminary Report (1887), particularly the overview of Slade’s methods, printed pages 8–13, and the dated sittings, discussion, Pepper memorandum and correspondence at pages 51–77. The relevant original text was read directly; the title and publication date were checked against the scanned title page. The report’s investigation began before 1885, but this case’s incident year is the year of Slade’s Philadelphia sittings.
Henry Slade in London, 1876 follows the different daylight accounts, interrupted performance and legal dispute. It should be read as a separate investigation, rather than treating either locality as proof of what happened at the other. Source review, image rights and metadata checked 13 November 2026.