In the summer of 1819, thirty-one years ago, then but a boy, I first saw these remarkable trees, lofty, venerable and flourishing. Being at Detroit last September, I paid many of them a visit in detail, for the purpose of a close examination. Those of your readers who are familiar with the Detroit river, need not be told that previous to the late war with England, and for several years after - perhaps until 1820 - its banks on both sides, from Lake Erie to St. Clair, were occupied almost exclusively by the descendants of the original French settlers, many of whom still remain. On their forms near the river, were, and still are, humble looking farm-houses, principally of logs, with but poor and inconvenient out-buildings; a small garden; a straggling orchard of apple, pear, and perhaps a few peach trees, currant bushes, etc, all under the most neglected culture, but even with these drawbacks, yielding bountiful crops of fruit. They were, too, of natural varieties; grafting, if even known, never being practiced among the French habitans of that insulated region.

Detroit, Sandwich and Maiden, were the only towns upon the river, and they small trading and military posts, which were the only markets for the meagre products of the indolent people who farmed, fished and hunted in their neighborhoods. These settlements were commenced about the year 1670 - one hundred and eighty years ago - and but fifty years after the Pilgrim landings at Plymouth. To those familiar with the agriculture of the Canadian French, of whom these people were a part, the exhausting and wasteful farming practiced by them needs no description. None can be worse, as the frequent old mounds of barn and chip manure now to be found around the former and present sites of their dwellings, and the worn and desolate appearance of their exhausted fields, too plainly testify.

Taking a horse and buggy at Detroit, I rode for several miles up the river, nearl to the foot of Lake St. Clair. On the out-skirts of the city, these old pear trees arc occasionally seen, towering high above the house-tops, among the ancient apple and other trees; but the greater part of them have been rooted out in the opening of streets, and building up of the town. Two or three miles out, where the old French farmers remain undisturbed - and they chiefly so remain, both in their use and occupants - for cultivation they cannot be said to have - these grand old trees begin to show in all their vigor and maturity. Ten, twenty, and in some instances more, may be counted in a field adjoining a dilapidated old farmery near the river; some in rows like avenues, others scattered about in groups, and occasionally struggling for supremacy among an ancient orchard of enormous apple trees. I stopped at several places, went into the grounds and carefully examined the trees. I girted several with a line, and found them to measure six to nine feet in circumference at three feet from the ground.

They towered up in many instances, fifty to sixty feet high, with grand, spreading tops, and though some of them had occasionally dead limbs among their branches, and others had lost parts of their tops by the most heedless and barbarous cutting out, leaving large, stumpy, decayed hollow luts, and others broken and torn out by winds or over-bearing, the main trunk and branches looked vigorous and healthy. shouing wonderful. The choky taste of the wilding, which I have no doubt they are, and are chiefly used for cooking, drying and preserves. Some of them are ripe in August, and but few of them last beyond September; and the great majority of the fruit, as I was told, is about the size of those I saw. The oldest person I could find to learn any thing of their age and history, was an old French woman who was born on the farm where I saw her. She did not know her own age exactly, but I gathered from her talk that she was full seventy years old. She informed me that the trees in her orchard were apparently as large as they now-are when she was a child; but by whom, or when they were planted, she could give no account.

The seeds unquestionably, were brought from France at the first settlement of the country, and in all probability, the trees must be much more than a century, probably a hundred and fifty years old, and from present appearances they may, with ordinary care, hold on full another hundred years.

I got a spade and dug on several different farms among the trees, and found the soil invariably a heavy, strong, clayey loam - some would call it cold and clammy - highly charged with lime, and resting on a clay subsoil - an almost dead level, and elevated but a few feet above the river; and although it had been worked ever since, and probably years before the trees were planted, did not appear to be exhausted in its fruit-sustaining properties. This is the predominating soil, both on the Detroit and Niagara rivers, and finer, larger, and more fruitful trees are not to be found, than are produced on the banks of these rivers, particularly in the old settlements; and up and down, as they were seen from the water, on both shores of the Detroit river, the old pear and apple trees had the like appearance. Nor had the land been drained at all, that I could discover, but was just in its natural condition.

Now, whether if these had been worked trees of the finer kinds of fruit, they would have lived to this advanced age and great bearing, I am unable to determine. But certain it is, that in hardihood and vigor no fruit trees can excel them. And it is an interesting fact for pomologists to learn, that we have a soil in which the pear will flourish equal to any other tree known - and to those who wish to cultivate this valuable fruit to high perfection, it is worth while to know that in such a soil - a lime stone, clayey loam - they will thrive successfully, while in a sandy, primitive soil, they certainly are short-lived, and fruit badly, unless effectually fed with lime and ashes.

An inference or two drawn from the history and position of these ancient trees, may be worth consideration. Is not the stock of the seedling pear hardier and more vigorous than the worked stocks of the more refined and delicate wooded fruits? And if so, is it not the better plan to grow our pears of such seedling stocks up to the branching point, and then work them with the desired varieties? It so appears to me.

I am informed by some intelligent cultivators of fruit, natives of Normandy, that in the heavy soils, particularly about Rouen, the pear grows with a luxuriance rarely seen in America, and the now almost universal practice among our nurserymen, of importing French seedlings in which to work their pears - thus avoiding the early leaf blight, so prevalent among their own seedlings - would seem almost conclusive proof that there is a soil which is almost exclusively adapted to the successful culture of this tree beyond any other.

Try, they do crack, and shrivel, and spot. The evidence seems to me to be conclusive, particularly with this variety.

There are instances, undoubtedly, where large, flourishing and aged pear trees are found in light soils; but on examination it will be ascertained that such trees are favorably located to receive the wash of the house, out-buildings, or yards, which are rich in lime and potash, thus feeding them highly on the material so necessary to their full development and bearing. And the fact that the plum is so successfully grown in the stiff clays of Schenectady, Albany and Hudson, and other portions of the Hudson river valley where the peculiar "Albany clay" predominates, over other apparently more congenial localities, is an evidence that soil, more than cultivation, has to do with the success of many of our better fruits.

May not the history of the Detroit Pear trees also throw some light on the doctrine of special manures as a panacea for barrenness and want of growth, in many of our fruit trees, standing on light, loamy and sandy soils? For here is the living fact, of trees, in all probability one hundred and fifty years old, of enormous growth, and in full vigor, annually loaded with large, fair, perfect fruit, standing out in open fields - and so long as the trees have stood there - under an exhausting, wasteful course of tillage, with little or no artificial manures of any kind. What an enormous draft of the constituents of the wood, leaf, and fruit of the pear, has been made on that soil; and still, to all appearance, not lacking in the requisite aliment to sustain them for many years to come! A most interesting subject of examination this, to the physiologist. That many of these old trees might now be benefitted by a thorough incorporation into the soil of wood ashes, decayed leaves, rotten wood, spent tan-bark, lime, and barn-yard manure, I have no doubt; for beyond all question, some individual spots where they grow, judging from the waning appearance of the trees, must be well nigh exhausted of their fruit-growing elements.

I once knew an old apple tree - perhaps it had stood a century or more - the last survivor of an orchard, its branches mostly gone, its trunk decayed and hollow, brought into a vigorous new growth and bearing, by the application of chip manure and leached ashes, upon the surface beneath it. I knew an old pear tree which stood in a deserted garden, beside a stone wall, and with but a small part of its trunk left, (the rest had rotted off and fallen away,) yet by renewed cultivation, replaced with a new top and branches, which became fruitful, and made a rapid growth of new lark and wood on the decayed trunk. They were on moist, sandy-loam soils.

If I lived in the neighborhood of Detroit, I certainly - if I could get the privilege - would try the virtues of decayed wood, lime and ashes, on one or more of those declining pear trees, and know the result; and it is greatly to be wished, that while they still survive, some one in their immediate neighborhood may feel sufficient interest in the subject to make the proper application, and let the public know the result. Lewis F. Allen.

Black Rock, December, 1850.