_April 3d._—The Professor sat up last night as he intended, and found his watch, which was shared by one or two of his young assistants, very interesting. We crossed the Gulf Stream opposite Cape Hatteras, at a latitude where it is comparatively narrow, some sixty miles only in breadth. Entering it at about six o’clock, we passed out of it a little after midnight. The western boundary of the warm waters stretching along the coast had a temperature of about 57°. Immediately after entering it, the temperature began to rise gradually, the maximum being about 74°, falling occasionally, however, when we passed through a cold streak, to 68°. These cold streaks in the Gulf Stream, which reach to a considerable depth, the warm and cold waters descending together in immediate contact for at least a hundred fathoms, are attributed by Dr. Bache to the fact that the Gulf Stream is not stationary. It sways as a whole sometimes a little toward the shore, sometimes a little away from it, and, in consequence of this, the colder water from the coast creeps in, forming these vertical layers in its midst. The eastern boundary is warmer than the western one, for the latter is chilled by the Arctic currents, which form a band of cold water all along the Atlantic shore. Their influence is felt nearly to the latitude of Florida. On coming out of the Gulf Stream the temperature of the water was 68°, and so it continued for an hour longer, after which Mr. Agassiz ceased his observations. To-day some of the gulf-weed was gathered by a sailor, and we found it crowded with life. Hydroids, in numbers, had their home upon it; the delicate branching plumularia and a pretty campanularia, very like some of our New England species; beside these, bryozoa, tiny compound mollusks, crusted its stem, and barnacles were abundant upon it. These are all the wonders that the deep has yielded us to-day, though the pretty Portuguese men-of-war go floating by the vessel, out of reach thus far. Such are the events of our life: we eat and drink and sleep, read, study Portuguese, and write up our journals.