103. Read the following passage, then answer the question below.

Before the eighteenth century, cloth in Britain was made largely by households. Spinners turned raw fiber into thread on simple wheels, and weavers wove thread into cloth on hand looms, often in cottages, with merchants delivering materials and collecting finished goods. The system was slow, and spinning in particular was a bottleneck: it took several spinners to supply enough thread for a single weaver. The inventions that began to break this bottleneck in the 1760s and 1770s, including James Hargreaves's spinning jenny and Richard Arkwright's water frame, allowed one worker to produce many threads at once.

Arkwright's machine required more power than a person could supply, so it was installed in mills beside rivers, where water wheels turned the machinery. The factory therefore arose partly from a technical need: machines had to be gathered where power was available, and workers had to come to them. Later, steam engines freed mills from riverbanks and allowed them to cluster in towns such as Manchester, whose population grew many times over in a few decades.

Historians disagree about how much the factory improved lives. Cotton became far cheaper, which benefited consumers, and wages in some mills exceeded those of farm labor. But working hours were long, discipline was strict, and children, who were paid less than adults and could reach small spaces beneath machinery, made up a substantial part of the workforce. Reformers pressed Parliament to regulate conditions, and a series of Factory Acts limited child labor and working hours in the nineteenth century. Because the technology originated in Britain, other countries saw the factory both as a model and a threat; Britain tried for decades to forbid the export of machines and the emigration of skilled workers, but its monopoly eventually collapsed.

Why were Arkwright's machines installed beside rivers?