How was the keyboard arrangement structured in Sholes's earliest typewriter prototypes?

A two-row arrangement that was largely alphabetical.

The very first designs that Sholes and his initial collaborators experimented with featured a keyboard layout that was organized primarily in alphabetical order across two rows. While this arrangement seemed logical from a linguistic standpoint, it proved mechanically disastrous for the early typewriter hardware. Because letters commonly used together in sequence (bigrams) were placed adjacent to each other, rapid typing caused the corresponding type bars to clash and jam the mechanism. This specific mechanical bottleneck was the direct impetus for the complex trial-and-error engineering process that eventually yielded the QWERTY structure.