Manuel del Río was a Spanish Franciscan, said to have been a skilled watchmaker, who probably learned the trade in Oporto, Portugal, with Tomás Luis de Sáa. Del Río belonged to the Franciscan community in Santiago, where in 1759 he published Arte de los reloxes de ruedas (The art of making mechanical timepieces). The work was reissued in 1789 in Madrid by del Río’s disciple Ramón Durán. That edition is presented here. The prologue states that one of the reasons for writing the book was the lack of manuals on the subject. In fact, two other Spanish books on watchmaking were published in the second half of the 18th century. The singularity of del Río’s work resides in its being the first to describe church clocks and to provide instructions on their manufacture. Del Río flourished in the favorable cultural environment created by King Charles III, who promoted the teaching of industrial and artistic trades and the publication of scientific and technical works. The king’s policies also led to the founding of centers such as the Royal Clockmaking School in 1771 and the Royal Clock Factory in 1788. By this time, use of mechanical clocks had become so widespread that there was a demand for manuals to help owners to maintain them and to correct their timekeeping. The work shows many of the characteristics common to 18th-century books intended for the spread of utilitarian knowledge. Included are engravings of instruments, gears, and other objects, arranged to help explain how they functioned. The illustrations are by Cipriano Maré, an engraver who contributed to other important popular science works. The book is well organized and includes a question and answer section in the first volume and an alphabetic subject index and a glossary in the second that reflect its didactic purpose.