LEAVING Havana near the close of March, our American party found good accommodations on the steamer Empire City; on board were about one hundred of Walker's men then returning as the forlorn hope from the disastrous campaign in Nicaragua. They were very badly off for everything, and no doubt suffered much for clothing during part of our passage to New Orleans.

Voyages by steam have now become so common that descriptions of them must be omitted by travellers who expect to be read. Suffice it, that the Delta of the Mississippi was safely reached in a heavy fog - that our pilot mistook his position and entered a pass quite too shallow for our lumbering ship - that we spent a whole day in the mud, with the paddles going, and passengers irritated, till relieved by a tug and the swell created by two ships in charge of a steamer passing under our lea, and within jumping distance.

This bar at the mouth of the mighty river occasioned much talk; and some green men declared that if it existed in places they knew of the merchants .would clear it out every day rather than submit to such an annoyance I forgetting the difficulties occasioned by the immense mass of rolling waters which descend filled with the light debris of the country above.

The water at the bar at the mouth is fourteen feet in depth, which is double that of the Nile, Euphrates, Indus, Ac, and fortunately does not grow shallower; five miles above the sea the river is found to be still one hundred and forty feet deep; here, as well as above, its current at the surface and on the bottom has nearly an equal velocity. At New Orleans Professor Drake, in 1844, found the depth to be two hundred and forty feet. This extraordinary depth affects the imagination with a strange feeling of awe as one looks at the surface, resembling externally that of other rivers we are accustomed to, which present to the eye a much greater volume; the impression is enforced by the remark that no one who has the misfortune to fall into its current ever comes up alive. The ages and ages that it has been running one road have elevated its banks without raising its bottom. The Thames, Loire, Po, Elbe, Vistula, Danube, Dnieper, Don, and Volga united, fall short of the Mississippi nearly one third in the volume of their waters; the vastness of the idea is increased when we remark that during a greater portion of the year this river affords a navigation equal to the circumference of the globe.

Of the successive layers of cypress swamp known to exist on the banks, it is sufficient to refer those in search of knowledge to Lyell and other recent writers who have unfolded the wonderful operations of this mighty stream for successive ages, developing from the water, grass preceding the cypress, and the cypress the live oak. The elevation of the grass zone is assumed to have occupied 1,500 years, corresponding nearly with the known elevation of the Nilotic valley, and some go so far as to assert that the whole geological formation has consumed a period exceed-, ing 158,000! Sir C. Lyell estimates it at 60,000 years. How dwarf and pigmy is man; measuring the life of the present inhabitants by these opinions, their existence seems comparable only to the life of a fly that settles on a grain of sugar, and is brushed away forever by a breath of air.

As we ascend the river the mind must continually recur to the vastness with which the silent operations of nature are here conducted - so slowly that daring the existence of three generations there is made scarcely as much impression as would be created by placing a grain of fine sand in a teacup or a pitcher of water, and yet so surely that its effect after thousands of years, are astonishing and tangible. Awe must take possession of the most frivolous minds as the successive phenomena of the great Delta are rapidly exposed to view.

Ascending as we did much of the distance in the night, less opportunity for observation than would have been agreeable was afforded; the smell of orange groves frequently filled the cabins; as day dawned we saw the plantations of this fruit in considerable numbers; one or two are very celebrated for the quantities they produce, and we could but remark that these were sheltered by plantations of forest trees around them to keep off the northern blast, and to protect them from high winds which would scatter the fruit; thus, we see the importance of this kind of protection even on the borders of the tropics, and in the region of the orange and the cane; how much more important in our colder clime, and especially on those prairies still open to the coldest blasts from the lakes.

New Orleans reached, we took an early stroll through its level streets, and were again interested to see the trees in full leaf and bloom before the advent of April. The sour-orange trees were loaded with golden fruit as in Cuba; the roses were magnificent, climbing to the tops of the houses; the Locust and the Pride of India, favorite street trees, the latter especially, were in full beauty. At the shops a few strawberries without much flavor had made their appearance, and we were delighted to see at this early date at the fruit stores a ripe yellow fruit of the medlar family, here called the Mespilus Plum, which blossoms in December, and is now sought for here with greater avidity than any fruit planted at the north. It is oblong, with small seeds said to contain much prussic acid, and possesess an agreeable acidity.

It is highly pleasant to find one's self on American soil again; coming from Havana, New Orleans has a homish look, which it would scarcely possess if approached from up the river. So lately from the tropics, the dress, hats, Ac, were all different from what we had so recently left; and it was very striking to see people perambulating without cigars in every mouth.

A few remarks on New Orleans and the garden of Henry Lawrance, an enthusiastic horticulturist, will not detain us long, when we shall ask the reader to accompany us on a trip to Natchez, where there is much to interest the lover of gardens.