The quest for a repeating handgun took some strange turns on the way to the revolving cylinder.
This particular oddity is known as a Harmonica Gun, because of the distinct appearance of a steel slide that contained a number of chambers.
It’s a firearm innovation that preceded the perfection of the centerfire cartridge. On the earliest models, each chamber was breech-loaded with a powder charge, projectile, and percussion cap. You could say this design’s heart was in the right place, but it just didn’t quite get there as a practical repeater.
The slide was inserted into the breech. After firing a round, the shooter released a camlock to advance the slide through the gun. The problem was, each chamber had to be lined up with the barrel and hammer by hand. There were no indexes or mechanism to progress the slide. On later models, this was rectified, with some double-action models produced that advanced the slide through the gun to a new chamber as the trigger was pulled. But it was still bulky and awkward.
A famous maker of harmonica guns was Jonathan Browning, the father of even-more-famous John Moses Browning. He began making the guns in 1834 in Quincy, Illinois, along with more conventional revolving rifles.
This video from Forgotten Firearms shows two examples of harmonica gun designs. These two are pinfire weapons manufactured by Jarre, which used metallic cartridges that basically had a primer inside the brass case with a tiny firing pin extending from the primer and protruding through the top of the case. A second type of harmonica gun, shown in the video, uses a slide with a small barrel attached for each chamber, instead of a stationary barrel.