What exactly are these old glass jar battery things found in a 1911 basement?

Those are almost certainly **Leclanché cells**, wich were the standard wet-cell batteries used for residential telephone systems and doorbells back in the early 1900s. Before we had reliable low-voltage transformers to step down mains power, these jars provided the small amount of voltage needed to run signaling equipment. You’d ussually find them in a group of two or three tucked away in a cellar or a closet near where the original phone line entered the house.

The setup usually consisted of a glass jar filled with a solution of ammonium chloride—basially sal ammoniac—with a carbon rod and a zinc rod acting as the electrodes. Over a century, the water has probably evaporated, leaving behind a white, crusty salt residue on the glass and the metal terminals. That stuff is corrosive, so you defintely want to wear some heavy nitrile gloves if you decide to move them. The heavy fabric-insulated wiring you're seeing is typical for that era. It’s often a single copper conductor wrapped in cotton or silk, sometimes treated with wax or bitumen. It’s brittle now, and the insulation will likely crumble if you bend it too sharply. If the jars are still liquid-filled, be extra careful. The electrolyte isn't as nasty as modern car battery acid, but it’ll still eat through fabric and irritate your skin.

I’ve pulled dozens of these out of old Victorians and foursquares. Most of the time, I just leave them be if they aren't in the way of new work, but if you need the space, double-bag them in heavy contractor bags. The glass can get surprisingly fragile after sitting in a damp crawl space for a hundred years. It’s a neat piece of electrical history, but definitely treat the contents with a bit of respect.

That is wild. I didn't realize houses used to have thier own little power plants just for a doorbell. If I find somthing like that, is there any danger of a shock even if they've been sitting there for 100 years? I'd be worried about touching the metal parts. Also, do people actually collect these things or are they just straight-up trash? I’d hate to toss out something that belongs in a museum, but I also don't want a chemistry project leaking in my garage.

Zero chance of a shock—those things are chemically dead. Even brand new, they only put out about 1.5 volts, so it wouldn't have tickled much back then anyway. As for value, don't toss them! Collectors go nuts for the embossed glass jars, especally if you find names like 'Columbia' or 'Edison' stamped on the side. If the porcelain insulators on the lids aren't cracked, you’ve got a solid piece of history. I’ve seen the rarer variants go for fifty bucks or more at swap meets. Just be careful cleaning the glass; that old residue can permanently etch the surface if you're too aggressive with the scrubbing.

Watch out for the smell if there’s any moisture left in those jars. Even if they look dry, as soon as you disturb that residue, it can put off a wierd, metallic funk that stays in a cramped crawl space. I ussually bring a small shop vac with a HEPA filter to suck up the loose flakes before I even touch the glass. Also, check the floor under them; sometimes that ammonium chloride leaks out and eats right into the wood or concrete over the decades. It leaves a nasty white stain that's a total pain to seal over if you're trying to finish that space.