Black Waters. —The enigmatical phenomena of the so-called “black waters” of certain tributaries of the Orinoco are, in reality, of a coffee-brown colour, which, in the shade of palm groves, seems almost to pass into inkblack. When placed in transparent vessels, the water appears of a golden yellow. The image of the Southern Constellation is reflected with wonderful clearness in these black streams, and when they flow gently, they afford to the observer engaged in taking astronomical observations a most excellent artificial horizon.—Idem.