Broad Run, the next stream of consequence east of Goose Creek, rises in Prince William County and pursues a northern course, with some meanderings through Loudoun. It flows into the Potomac about four miles below the mouth of Goose Creek. Sugarland Run, a still smaller stream, rises partly in Loudoun, though its course is chiefly through Fairfax County, and empties into the Potomac at the northeastern angle of the County. In its southeastern angle several streams rise and pursue a southern and southeastern course, and constitute some of the upper branches of Occoquan River. Perhaps no county in the State is better watered for all purposes, except manufacturing in times of drought. Many of the farms might be divided into fields of ten acres each and, in ordinary seasons, would have water in each of them. There are several mineral springs in the county of the class called chalybeate, some of which contain valuable medicinal properties, and other springs and wells that are affected with lime. Indeed, in almost every part of the County, there is an exhaustless supply of the purest spring water. This is due, in great part, to the porosity of the soil which allows the water to pass freely into the earth, and the slaty character of the rocks which favors its descent into the bowels of the hills, from whence it finds its way to the surface, at their base, in numberless small springs. The purity of these waters is borrowed from the silicious quality of the soil. The largest spring of any class in the county is Big Spring, a comparatively broad expanse of water of unsurpassed quality, bordering the Leesburg and Point of Rocks turnpike, about two miles north of Leesburg. The springs, as has been stated, are generally small and very numerous, and many of them are unfailing, though liable to be affected by drought. In such cases, by absorption and evaporation, the small streams are frequently exhausted before uniting and often render the larger ones too light for manufacturing purposes. Nevertheless, water power is abundant; the county's diversified elevation giving considerable fall to its water courses, and many sites are occupied. CLIMATE. Because responsible statistical data is usually accorded unqualified credence, it is without undue hesitation that the following bit of astonishing information, gleaned from a reliable source, is here set down as positive proof of the excellence of Loudoun's climate: "It (Leesburg) is located in a section the healthiest in the world, as proven by statistics which place the death rate at 8-1/2 per 1,000, the very lowest in the table of mortality gathered from all parts of the habitable globe." The climate of Loudoun, like that of most other localities, is governed mainly by the direction of the prevailing winds, and, to a limited extent, is influenced by the county's diversified physical features.