II
All waters are classed as either standing or running; they are either gathered in one or occupy different channels underground. Some of them are sweet, others have pungent flavours of different kinds, among them salt, bitter, medicinal. Belonging to the last class one may name sulphur, iron, alum waters. The taste shows the quality. Waters of different kinds have many other differences. First there is touch, hot and cold; then weight, light and heavy; then colour, pure, muddy, dark blue, yellowish; then wholesomeness, wholesome and useful, or deadly or capable of petrifaction. Some waters are thin, some thick; some give nourishment, others pass through the system without benefiting it at all; the use of some removes barrenness.