Phantom Thermometer

Phantom Thermometer — a calibrated instrument of the Tower used to register thermal displacements produced by interaction between Ideational Silica and Phantom Pollen. The device is governed in specification by the Seventh Concordance, which formally defines the Phantom Thermometry Scale and classifies the pollen employed in its operation as a 'Category III Environmental Phantom'. No Phantom Thermometer is considered operative unless its readings have been reconciled against the master instrument housed on Floor 44.

Construction and Component Doctrine

A standard Phantom Thermometer comprises a column of Ideational Silica seated within a torus of Attenuated Nickel-Silver, the latter being the same drafting alloy prescribed for use with Phantom Vellum. When Phantom Pollen of no less than Sigma-3 grade is introduced to the measurement plates, the silica undergoes a thermal displacement proportional to the local phaneric field. The Seventh Concordance, Annex 2, states that "the column shall not be filled with any substance cognisable by the ordinary senses, and its zero mark shall correspond to the absence of phaneric dependency as logged on Floor 44." Early recensions of the Third Concordance permitted a mercury analogue, a provision repealed in the Recension of 1181 after the Phantom Librarian of the West Stairwell observed that three such instruments had quietly ceased to exist during a Silent Interim.

The Master Instrument of Floor 44

The master Phantom Thermometer on Floor 44 serves as the sole calibration standard for all subordinate devices. Every fifth decade, a procession of West Stack clerks conveys candidate thermometers upward or downward to Floor 44 for concordance. The master's readings are transcribed onto Phantom Vellum using Attenuated Nickel-Silver tools, a method also required for any catalogue amendment referencing a Bibliographic Phantom. In winter of the year 882, a discrepancy of eleven silvan units was recorded between the master and the field instruments of the North Aperture; the Disputation on the Phantom Page records that the divergence was resolved by declaring the master instrument to have been "provisionally asleep" and thus non-binding for that season.

Measurement Practice and the Phantom Thermometry Scale

Readings are expressed in the units of the Phantom Thermometry Scale, from which the silvan measurement is derived. The scale quantifies the phaneric field dependency of Phantom Alloys and is referenced in the logging of Phantom Clock outputs within the Phantom Catalogue of Floor Ξ-9. During a Silent Interim, accumulation of Phantom Pollen on designated plates is an authorised substitute metric for Phantom Clock calculations, though the Seventh Concordance cautions that such substitution "does not relieve the officer of record from preparing the usual vellum, only from interpreting it." Sifted pollen at Sigma-3 grade additionally luminesces in patterns that outline the logical structure of Phantom Appendices, a property exploited by the scriptoria when verifying a Documentary Phantom.

Disputes of Specification

The Concordances disagree on whether a Phantom Thermometer may be constructed without Ideational Silica. The Third Concordance implies that any silvan-reactive medium suffices, whereas the Seventh Concordance holds silica to be indispensable. The resulting uncertainty produced the office of the Anticipatory Phantom registrar, who is charged with recording thermometers that have not yet been assembled. Clerk Orrin of the Lower Spiral filed a grievance in 994 asserting that his own thermometer had been catalogued as anticipatory despite standing on his desk; the Phantom Librarian of the West Stacks denied the petition on the ground that "a device observable without instrumentation is not yet phantom enough to require exemption."

Incidents and Annotations

In the winter of 1003, a Phantom Thermometer on the Eastern Mezzanine registered a negative thermal displacement of four silvan units following contact with an uncatalogued wool specimen later identified as belonging to a Phantom Sheep. The incident was recorded without conclusion in the Phantom Catalogue of Floor Ξ-9 and is cited in subsequent disputes concerning the boundary between environmental and animal phantoms. Visitors to calibration chambers are prohibited from bringing uncovered flame, as the master instrument on Floor 44 is held to misinterpret it as a Category III event.

"No thermometer of the Tower shall be trusted beyond the last concordance signed upon Phantom Vellum, and even that trust is provisional upon the silence of the appendices."

— Disputation on the Phantom Page, Section 9

The study of Phantom Thermometers remains under the perpetual amendatory authority of the Seventh Concordance, subject to such contradictions as later Concordances may introduce without notice.