In his book The Sex Life of the Foot and Shoe, William A. Rossi writes, “Foot fetishism or intense foot partialism is common enough to have earned itself a medical term, equus eroticus.” Erotic horse?! Is Rossi kidding? How is “erotic horse” relevant to feet? I simply do not get it. Cecil, please explain.

–J.K., West Covina, California

There does seem to be some confusion in the world of BDSM (bondage-discipline-sadomasochism) about the meaning of equus eroticus. I found only a few references to it in the sense of foot fetishism, none of which shed any light on the term’s origin. But who cares? The more common and interesting meaning is “ponyplay”–that is, an erotic scenario in which you treat your partner like a horse. If you’re into props, which seem to be a big part of the BDSM scene, you can rig up your pal (or have him/her rig you) in a full leather harness, complete with blinders, bridle, and bit.

I know what you’re thinking: Whoa! You can have show ponies, ponies pulling their masters in carts, and of course your basic horsey rides. There’s even a magazine called Equus Eroticus for those wanting to give free rein to their passion. Suffice it to say you’re not going to get the Boy Scouts selling subscriptions door-to-door.

Too weird? I’m not claiming it’s the ideal thing for a first date. But ponyplay buffs say it’s all in fun. (For more info, see the ponyplay FAQ–there’s a FAQ for everything on the Internet–at Me, I’m to the point where nothing surprises me. Once I joked about somebody coming up with a Web site for appendectomy-scar fetishists. Soon after, I got an E-mail. “If you ever do find an appendectomy-scar site,” it read, “let me know.”

WOW! I may have the distinct pleasure of catching the Straight Dope in an error. It regards a question that once enabled me to win a bet with a retarded ex-girlfriend and her Mensa mom: Is glass a liquid or a solid? I was taught that it was a supercooled liquid, and the dictionary concurred. What’s more, in answering the question “How come you can see through glass?” you yourself said, “Despite its appearance, glass is really a highly viscous liquid rather than a solid” (The Straight Dope, page 120). Needless to say, I was able to stick it in their proverbial eye. Recently, however, I have heard that glass isn’t a liquid, it’s an amorphous solid. Now who’s going to open their eye big and wide for me? Please don’t start tap-dancing and say it’s all relative. We all know the world is black-and-white. Glass, solid or liquid?

–Shayne Kislack

PS: Please let me know if I’m eligible for some sort of prize.

Now, Shayne. The mark of a truly great mind isn’t whether you’re right or wrong. It’s how well you can weasel out of a jam.

Lesser folk might prefer it otherwise, but there’s no sharp line dividing liquids and solids. A supercooled liquid, the term applied to glass for many years, has been rapidly chilled past its normal freezing point and apparently become solid without assuming the regular crystalline structure typical of solids. The term du jour, amorphous solid, means an apparently solid substance that lacks crystalline structure and instead has the random organization of liquids. In other words, we used to think of glass as a solidlike liquid, and now we think of it as a liquidlike solid. Big frickin’ deal.

I concede that changes in the properties of glass once it cools past the “glass transition temperature” are an argument for calling it a solid. But to my mind the real question is whether glass flows, as liquids do. I am happy to say it does, just not very fast. In the original column I wrote, “At room temperature [glass’s] rate of flow is so slow that it would take billions of years to ooze out of shape.” In the October 1999 issue of Discover, Yvonne Stokes, a mathematician at the University of Adelaide in Australia, says that it would take at least ten million years for a windowpane to get 5 percent thicker at the bottom. So not only was I essentially right, I was being conservative by a margin of 100 to 1.

Art accompanying story in printed newspaper (not available in this archive): illustration/Slug Signorino.