Complex sentence: The oldest of these were horizontal Janders in which the force of the water, striking a simple paddle wheel set horizontally in line with the flow turned a runner stone balanced on the rind which is atop a shaft leading directly up from the wheel.
Split into simpler sentences: The oldest of these were horizontal janders in which the force of the water would strike a simple paddle wheel set horizontally in line with the flow. This then turned a runner stone balanced on the rind atop a shaft leading directly up from the wheel.