This article analyses the improvement of cotton-spinning technology in the decades after the great inventions of Hargreaves, Arkwright, and Crompton. While the initial transition from hand to mechanised spinning has been well researched, our understanding of the types and sizes of spinning machines used in the U.K. between the 1780s and the onset of factory statistics in the 1830s is largely based on the experience of high-profile firms, or on specific technologies or regions. A new dataset of c1500 newspaper advertisements allows us to examine the temporal and spatial dimensions of the transitions from jennies to mules and from water frames to throstles as well the increases in the number of spindles carried by these different machines. They also show the rise of mills incorporating both continuous and intermittent spinning. A three-fold increase in machine size contributed a third or more to the large increases in output of yarn per worker and are testimony to the importance of continuous improvement in spinning machines. The newspaper advertisements also reveal that England, Scotland and Ireland remained largely distinct markets for used machinery in the nineteenth century, with Glasgow, Belfast and especially Manchester becoming increasingly the places to advertise.