On the 17th of May, nearly a month after our arrival in Rio, this cloud was interpreted to us. It was, indeed, charged with the issues of life and death, for it was on this day and the following that the final assaults on Petersburg were made, and the cloud which marred an otherwise stainless sky, as we were passing along the shores of Virginia, was, no doubt, the mass of smoke gathered above the opposing lines of the two armies. Footnote 3: The species of Hydroids most numerous upon the gulf-weed have not yet been described, and would form a valuable addition to the Natural History of the Acalephs. For an account of the animals of this class inhabiting the Atlantic coast of North America, and especially the New England shores, I may refer to the third volume of my Contributions to the Natural History of the United States, and to the second number of the Illustrated Catalogue of the Museum of Comparative Zoloögy at Cambridge.—L. A. Footnote 4: “This stream,” he writes, “is probably generated by the great accumulation of water on the eastern coast of America, between the tropics, by the trade-winds which constantly blow there.” These views, though vaguely hinted at by old Spanish navigators, were first distinctly set forth by Franklin, and, as is stated in a recent printed report of the Coast Survey Explorations, “they receive confirmation from every discovery which the advance of scientific research brings to aid in the solution of the great problem of oceanic circulation.” Footnote 5: No one can read the account of the explorations undertaken by the Coast Survey in the Gulf Stream, and continued during a number of successive years, and the instructions received by the officers thus employed from the Superintendent, Dr. A. D. Bache, without feeling how comprehensive, keen, and persevering was the intellect which has long presided over this department of our public works. The result is a very thorough survey of the stream, especially along the coast of our own continent, with sections giving the temperature to a great depth, the relations of the cold and warm streaks, the form of the ocean bottom, as well as various other details respecting the direction and force of the current, the density and color of the water, and the animal and vegetable productions contained in it. (See Appendix No. I.)—L. A. Footnote 6: