the idea for the spinning jenny is said to have come when a one-thread spinning-wheel was overturned on the floor, and hargreaves saw both the wheel and the spindle continuing to revolve. he realized that if a number of spindles were placed upright and side by side, several threads might be spun at once. the spinning jenny was confined to producing cotton weft threads, and was unable to produce yarn of sufficient quality for the warp. high-quality warp was later supplied by arkwright's spinning frame.