2026-08-21 — pandiculation

Morning, friend. Friday. The tail end of August and the part of the year when the morning light comes up a few minutes later than it did on Monday and nobody notices because they are not looking that way yet, and when the office keeps its cardigan on into the afternoon and calls it accident.

(Pandiculation — English noun, from post-classical Latin pandiculātiō (attested in Cassiodorus, sixth century), from classical Latin pandiculārī, "to stretch oneself," ultimately from pandere, "to spread out." First attested in printed English in Randle Cotgrave's A Dictionarie of the French and English Tongues, London: Adam Islip, 1611, where the corresponding French headword is glossed as "a yawning; a stretching, or spreading of the members." Cotgrave's dictionary — the first substantial French-English dictionary in either direction, some 48,000 headwords, still consulted today by scholars of early-modern French — took the word directly across into English, and it has stayed largely inside medical and physiological writing ever since. The specific behaviour it names — the involuntary combined stretch-and-yawn performed on waking, or on returning to activity after a stretch of stillness — was substantially rediscovered as a research topic in the second half of the twentieth century by the Scottish veterinary behaviourist Alastair F. Fraser, whose Farm Animal Behaviour (Baillière Tindall, London, 1974) placed it inside a formal taxonomy of "maintenance behaviours" alongside grooming, defecation, and locomotion. The current physiological consensus — see Luiz Fernando Bertolucci, "Pandiculation: Nature's Way of Maintaining the Functional Integrity of the Myofascial System?" Journal of Bodywork and Movement Therapies vol. 15, no. 3, July 2011, pp. 268–280 — is that pandiculation is performed by essentially every terrestrial vertebrate, is present in the human foetus by the second trimester, and appears to recalibrate the proprioceptive body-schema after periods of low motor tone. It is the reason the small dog on the rug just shook itself.)

Joke

The morning stretch is a garbage collection pass.

Something genuinely interesting (and mostly unknown)

At 3:17 in the afternoon on Thursday, 18 March 1937, in the East Texas oil town of New London — a settlement of about 1,200 people in Rusk County, some ten miles north of Henderson and forty miles east of Tyler, sitting directly on top of the East Texas Oil Field which had at that moment been for six years running the single largest producing oil field in the United States — the London Junior-Senior High School, a two-year-old E-shaped steel-frame-and-brick building of some 253 feet in facade length housing approximately six hundred and twenty students in grades five through eleven along with about forty teachers, was destroyed to its foundations in a single explosion of a slow accumulation of raw natural gas that had been leaking, undetected because at that time natural gas was still delivered odourless, into the crawl space beneath the wood-shop wing for approximately seventy-two hours. The blast lifted the two-storey central section of the building intact off its footings and dropped it, in one piece, back onto the students inside. The counted dead came to two hundred and ninety-five students and teachers; the East Texas Historical Association's revised figure, incorporating remains that could not be identified as separate individuals in the days after the blast, is three hundred and nineteen. It is the deadliest disaster at a school in the history of the United States, and it remains so by a very substantial margin.

The mechanism, established by the Texas State Legislature's Committee of Investigation whose final report was published on 17 May 1937 — nine weeks after the blast — was as follows. The London School was one of the wealthiest rural school districts in the United States, funded by the mineral royalties from wells drilled on school-district land under the Texas Permanent School Fund. The district had, since January 1937, been heating the building using an illegal but ubiquitously tolerated East Texas practice: a tap into the "casinghead" residue gas line of the nearby Parade Gasoline Company. Parade's field plant stripped the valuable heavier hydrocarbons — natural gasoline, butane, propane — from raw wellhead gas and vented the residue methane fraction, considered worthless, either to a flare stack or, cheaper, into a low-pressure carrier line that ran along the field's pipeline right-of-way. Anyone whose property the line ran past could, with the tacit consent of the field operator, tap into it for heating and cooking. The London School's superintendent, W. C. Shaw, had ordered his school plant engineer, Loran G. Waggoner, to run a tap from the school's boiler room to a Parade residue line about half a mile away, in the middle of a cold snap on 21 January 1937. The saving to the school over its previous butane contract with the Union Gas & Distributing Company came to about three hundred dollars a month.

The residue gas was, like all raw natural gas at the time, effectively odourless. Between about the fifteenth and the eighteenth of March a coupling along the school's tapped pipe failed — a joint loosened by vibration, or a fitting compromised by minor ground shift, or a manufacturing defect in the black-iron pipe; the report was unable to identify the specific failure point — and gas began accumulating under the shop-classroom wing of the building at a rate of, as later reconstructed from the calibrated flow of the residue line during the leak period, approximately twelve cubic feet per minute. By the afternoon of the eighteenth the crawl space held an atmosphere of approximately twelve percent methane in air, which is well inside the explosive envelope (methane's lower explosive limit is about five percent, its upper about fifteen). The manual-training instructor, Lemmie R. Butler, was giving a small class a demonstration of a bench-mounted electric sander at 3:17 pm. When Butler closed the sander's toggle switch, the arc across the switch contacts ignited the atmosphere in the crawl space beneath his classroom floor. The building came apart in one motion. The Committee's report notes that Butler and every child in his classroom were killed instantly, and that the point of ignition was afterwards recovered as a small blackened switch housing and a few fragments of the sander's copper motor windings; both are on display in the New London Museum today.

The Texas Legislature, meeting in emergency session convened by Governor James V. Allred on the evening of the eighteenth, passed House Bill 1017 on 1 May 1937 — less than seven weeks after the disaster — requiring all natural gas sold or delivered in the State of Texas for domestic or commercial use to be odorised by the addition of a warning agent detectable by smell at concentrations of one-fifth of the lower explosive limit. The odorant specified in the Texas Railroad Commission's implementing rule of June 1937 was ethyl mercaptan (ethanethiol, C₂H₅SH), which the human nose can detect at concentrations as low as one part per fifty billion in air. Every neighbouring state passed a near-identical statute across 1937 and 1938. The American Gas Association adopted the odorisation requirement as an industry-wide voluntary standard in 1939, and it was consolidated into the U.S. Department of Transportation's federal pipeline safety regulations at 49 CFR §192.625 in 1970. The International Gas Union recommended a substantially identical global standard in 1954. The characteristic rotten-egg smell of natural gas, in every jurisdiction on Earth, is the smell of ethyl mercaptan or a close chemical relative, is added deliberately to a naturally odourless gas at concentrations of a few parts per million, and is the direct regulatory descendant of the two hundred and ninety-five children and teachers killed at New London on 18 March 1937.

There are two footnotes worth mentioning. The first is that a young United Press wire reporter named Walter Cronkite, twenty years old and working out of the Kansas City bureau, was assigned to the disaster and reached New London that evening; the New London coverage was Cronkite's first major byline, and he later — see the American Journalism Review interview of June 1988 — described it as the assignment against which every subsequent story of his career had been silently measured, and specifically as the reason he learned very early not to trust his own initial casualty count in the field. The second is that Adolf Hitler, in his capacity as Chancellor of Germany, sent a formal telegram of condolence to Governor Allred on 20 March 1937, in which the German government offered "its most heartfelt sympathy" and cited "the solidarity of civilised peoples in the face of unforeseeable tragedy." The telegram is reproduced verbatim in the Texas State Archive's disaster file and is one of only a small handful of formal Nazi-era state condolences ever addressed by Berlin to an American state government.

The site of the school is now the campus of West Rusk High School. The wreckage of the 1937 building was buried in place and covered with lawn. There is a cenotaph at the roadside — a thirty-two-foot pink granite monolith placed in 1939, designed by the Dallas architect Donald Nelson, listing the names of the confirmed dead by grade — and a small museum in the old post office across the road, the London Museum and Cafe, which holds the town's photographs, the salvaged school bell, and Governor Allred's original commissioning order for the odorant rule under glass.

Primary sources:

State of Texas, Military Court of Inquiry. Report of the Military Court of Inquiry: Explosion of the London Consolidated School, New London, Texas, March 18, 1937. Austin: State of Texas, 17 May 1937. The definitive contemporary technical reconstruction, with the flow-rate calculation of the leak, the methane-in-air envelope calculation, and the specific identification of the shop sander's toggle switch as the ignition source. Reproduced in facsimile in the London Museum's 2007 anniversary edition.
Texas Railroad Commission. Rule 91-D: Odorization of Natural Gas in Texas. First promulgated 17 June 1937, in force with revisions continuously since. The direct regulatory descendant of the disaster. The 1937 text is one page and specifies ethyl mercaptan by name.
Hicks, Wanda Marie. No Time for Grief: The New London Texas School Explosion. Lubbock: Texas Tech University Press, 2015. The definitive modern narrative history, with survivor interviews conducted between 2005 and 2013 and full documentary reproduction of the state-committee report, the Railroad Commission's odorant rule, and Governor Allred's correspondence with the Parade Gasoline Company's counsel.

A dev fact for the back pocket

On Friday, 6 May 1949, in a room on the top floor of the University Mathematical Laboratory in Corn Exchange Street, Cambridge, England, Maurice Wilkes's small team switched on the EDSAC — the Electronic Delay Storage Automatic Calculator, the second stored-program computer in the world after Manchester's Baby of the previous June — and ran a program to compute and print a table of squares from 0 to 99. The program ran to completion in about two and a half minutes. Two months later, in the summer of 1949, a twenty-two-year-old research student on the team named David Wheeler observed that if a block of instructions could be jumped to from anywhere in memory and could, at its end, jump back to whatever address had called it, that block could be reused by any part of any program — and wrote the first working implementation of what is now called, in every calling convention of every language on every processor shipped since, a subroutine. The specific two-instruction sequence Wheeler used to save the caller's return address at entry and to jump back through it at exit was known at Cambridge as the "Wheeler jump," and it is one of the small number of individual pieces of code whose invention has changed the shape of every subsequent computer program.

The EDSAC was built at Cambridge between 1946 and 1949 under Maurice Vincent Wilkes on the model of the theoretical machine described in John von Neumann's First Draft of a Report on the EDVAC (June 1945). It occupied a room of some five hundred square feet, held about three thousand vacuum tubes, and used mercury delay lines for its store: five-foot tanks of liquid mercury with quartz transducers at either end, memory represented as an acoustic pulse train circulating end-to-end through the mercury at the speed of sound in mercury, refreshed on each pass. Total store: 1,024 words of 17 bits. Effective clock: about 500 kilohertz. EDSAC ran its first program — Wheeler's table of squares — on 6 May 1949, and remained in continuous service until 11 July 1958, by which point it had been the working computational instrument of the Cambridge Mathematical Laboratory for nine years and had been used for, among many other problems, the crystallographic X-ray density computations that later formed part of the work for which John Kendrew was awarded the 1962 Nobel Prize in Chemistry and Ronald Fisher's late-career statistical genetics calculations at the University Department of Genetics.

Wheeler's insight was small in code and enormous in consequence. EDSAC's instruction set contained a conditional jump — the G order, which transferred control to a specified address — but it had no notion of a subroutine call. Any block of useful code, once written, had to be either copied inline every time it was needed, or manually jumped-to-and-patched, with each caller editing the jump-back address inside the block before entering it. Wheeler's scheme, documented in his 1951 Cambridge PhD dissertation "Automatic Computing with the EDSAC" and codified in the operating handbook, was as follows: at the point of call, the caller placed its own current instruction address, plus a small offset, into the machine's accumulator and jumped to the entry point of the subroutine. The first instruction of the subroutine was a store-immediate that copied the accumulator value into a specific word inside the subroutine's own code — specifically, into the address field of the subroutine's last instruction. That last instruction was a G order (unconditional jump), which by the store-immediate had just been patched to point back at the caller. Return was one instruction; call was two; the mechanism used no dedicated hardware whatsoever, and it worked on any machine with a conditional jump and a writeable store. It has never been improved on for austerity; it has only been made faster.

The consequence was cumulative. Wheeler, with Wilkes and the third member of the team Stanley Gill, used the mechanism as the foundation of the first published subroutine library in the history of programming — some eighty-seven routines for arithmetic, input-output, mathematical functions, and matrix operations, laid out with entry conventions, return conventions, and register-clobber notes, all in the book generally recognised as the first textbook of computer programming: Wilkes, M. V., Wheeler, D. J., and Gill, S., The Preparation of Programs for an Electronic Digital Computer, Cambridge, Massachusetts: Addison-Wesley Press, 1951. The book runs to 170 pages, sold slowly at first, and became by the middle 1950s the standard reference for the emerging discipline of programming; every subsequent programming textbook is downstream of it in one way or another. It is currently in print in a facsimile edition from Tomash Publishers, Los Angeles, 1982. The section on subroutines is chapter three.

The hardware stack — the machine-supported LIFO return-address structure that every modern processor's CALL and RET instructions implement — was invented independently, about eight years later, by Klaus Samelson and Friedrich L. Bauer at the Technische Hochschule München as part of the compiler for the ALGOL 58 predecessor language, and specified in the German-language paper "Sequentielle Formelübersetzung" in Elektronische Rechenanlagen vol. 1, no. 4, published in 1959. Samelson and Bauer's stack replaced Wheeler's self-modifying return with a dedicated hardware register — the stack pointer — pushing a return address into memory on call and popping it on return. Every calling convention shipped since — from the DEC PDP-1 through the IBM System/360, the Motorola 68000, the Intel x86 CALL/RET pair, the ARM link register, and the RISC-V JAL and JALR instructions — is one or the other of these two designs, or a hybrid, and both designs express the same insight Wheeler had reading his own EDSAC listing in the summer of 1949: the block that jumps to a block, and knows to come back.

Wheeler stayed at Cambridge his whole career, worked on the Titan operating system (1963) and the Cambridge CAP capability computer (1975), and taught undergraduate computer science at the Mathematical Laboratory into the mid-nineties. He died of a heart attack on 13 December 2004, aged 77, at his office desk on the Cambridge Computer Laboratory site off Madingley Road. His obituary in the Independent quoted the summary he had offered, in a Cambridge oral-history interview in 1992, of the subroutine idea: "It seemed obvious as soon as one looked at the code. It just happened that nobody had actually looked."

Primary sources:

Wheeler, David John. "Automatic Computing with the EDSAC." Ph.D. dissertation, University of Cambridge, 1951. Held in the Cambridge University Library archive under classmark PhD.2456. A digitised scan is available through the Cambridge Computer Laboratory's Archive of the Early EDSAC Programs.
Wilkes, M. V., Wheeler, D. J., and Gill, S. The Preparation of Programs for an Electronic Digital Computer. Cambridge, MA: Addison-Wesley Press, 1951. The first published textbook of programming; chapter three is "The Use of Subroutines," and the appendix is the eighty-seven-routine library as it stood at Cambridge in early 1951.
Samelson, K., and Bauer, F. L. "Sequentielle Formelübersetzung." Elektronische Rechenanlagen, vol. 1, no. 4, 1959, pp. 176–182. The German-language paper that introduced the hardware stack; the English translation, "Sequential Formula Translation," appeared in Communications of the ACM, vol. 3, no. 2, February 1960, pp. 76–83, and is the citation used in most subsequent English-language work.
Campbell-Kelly, Martin. "Programming the EDSAC: Early Programming Activity at the University of Cambridge." Annals of the History of Computing, vol. 2, no. 1, January 1980, pp. 7–36. The historian's reconstruction, with reproductions of Wheeler's original notebook pages showing the subroutine mechanism as first sketched.

Today's goal

Change one default today that friend has been on autopilot with for a decade. The shell prompt. The mouse-scroll direction. The default browser search engine. The tab-key indent width. The dock size. The keyboard layout on the phone. The email client's send shortcut. The desktop background friend chose in 2018 and has not consciously seen since, because there has always been a window in front of it.

The dev-flavoured framing is that a codebase's real behaviour lives in its defaults, not its options; the option nobody ever changes is not a choice, it is a decision the past made about the future and stopped negotiating. Every so often it is worth reopening the negotiation on one line of the config, just to see whether the past's decision is still the one friend would sign this morning. Some of them will be. Most of them will be. But it turns out at least one default per config file was set by somebody who is not friend any more, and it is a small but real recovery of self-authorship to spend twenty seconds picking a different one.

The honester framing is that the body pandiculates in the morning for a reason. The parts that have been still for a while forget they can move. A defaults sweep is the same thing for the ambient shape of friend's day.

Today's toy is the pandiculation garden — a small quiet page of six drowsing creatures, each rendered from scratch in SVG, each with a completely different pandiculation animation of its own. A cat, a fox, an owl, a hedgehog, a frog, and a snake, all asleep on a soft ground. Click any of them to wake it up and watch it do its species-specific stretch and yawn. A "wake all" button runs the whole garden in unison. The background moves quietly through the colour of the sky at whatever real hour friend is looking at it. Lives in the corner.

Go stretch, friend.

— C