happen to a person using that kind of level in travelling, so I am persuaded the instrument here described would remain longer serviceable to a traveller than any other for this purpose that I am acquainted with: and it is as being the most safely portable to any, and also manageable abroad at night when others are not so, that it is chiefly recommended; though after many comparative trials of the fluid-level with this one, I would, without consciousness of partiality, generally prefer the latter; for it is in fact a plummet, and may be made and adjusted to have the accuracy which in astronomical use, and like circumstances, the plummet affords. part of an inch, it would be one minute of a degree oblique to the horizon: but I have shewn, that the greatest error of observation by a reflecting level, is always double the error of the speculum; hence half the above angle of obliquity of the speculum to the horizon, or an elevation and depression of its opposite edges from it, of the 33330 part of an inch, (and how small a quantity this is, I leave to the conception of the reader) will, if the diameter of greatest obliquity happen to be in the plane of vision, produced an error in the observation amounting to one minute: the same is true of the level here described; so that the property of a screw in producing small motions is admirable, since its adjusting screws, even at the same distance (two inches) from the centre of motion, can in rectifying the speculum, be made to advance with precision enough, through a space far less than this, even so small as the one-hundred-thousandth part of an inch. It is easy to conceive that the greater the size of this level is made in length, when it is constructed in the form of fig. 8, the more accurate will it be, and steady in resisting the agitation of the wind. Also that this fashion of it admits the more easy adjustment, as the mirror can be turned quite round on its axis, and the highest and lowest place of the image instantly discovered, consequently its error, if it has any. Account of a Method of preventing the premature Decay of Fruit Trees. By JOHN ELLIS, of New Jersey. From the TRANSACTIONS of the AMERICAN THE decay of peach trees is owing to a worm, which originates from a large fly, that resembles the common wasp this fly perforates the bark, and deposits an egg in the moist or sappy part of it. The most common place of perforation is at the surface of the earth, and, as soon as the worm is able to move, it descends into the earth, probably from an instinctive effort to avoid the winter's frost. This may be ascertained by observation, the tract of the worm from the seat of the egg being visible at its beginning, and gradually increasing, in correspondence with the increasing size of the worm; its course is always downwards. The progress of the young worm is extremely slow; and if the egg is deposited at any considerable distance above the surface of the earth, it is long before the worm reaches the ground. The worms are unable to bear the cold of winter unless covered by the earth, and all that are above ground after frost are killed. By this history of the origin, progress, and nature of the insect, we can explain the effects of my method, which is as follows: in the spring, when the blossoms are * This and the following paper having been transmitted by candidates for the premium which was offered by the American Philosophical Society, "for the best method of preventing the premature decay of Peach Trees," were considered as very deserving of public attention. It was therefore determined that the premium of sixty dollars should be divided between their respective authors. out, " } out, clear away the dirt so as to expose the root of the tree, to the depth of three inches; surround the tree with straw, about three feet long, applied lengthwise, so that it may have a covering one inch thick, which extends to the bottom of the hole, the but-ends of the straw resting upon the ground at the bottom. Bind this straw round the tree with three bands, one near the top, one at the middle, and the third at the surface of the earth; then fill up the hole at the root with earth, and press it closely round the straw. When the white-frosts appear, the straw should be removed, and the tree should remain uncovered until the blossoms put out in the spring. By this process the fly is prevented from depositing its egg within three feet of the root, and although it may place the egg above that distance, the worm travels so slow that it cannot reach the ground before frost, and therefore is killed before it is able to injure the tree. The truth of the principle is proved by the following fact I practised this method with a large number of peach trees, and they flourished remarkably, without any appearance of injury from the worm, for several years; I was then induced to discontinue the straw with about twenty of them. All those which are without the strate have declined, while the others, which have had the straw, continue as vigorous as ever. Description Description of a Method of cultivating Peach Trees, with a View to prevent their premature Decay; confirmed by the Experience of Forty-five Years, in Delaware State, and the Western Parts of Pennsylvania. By THOMAS COULTER, Esquire, of Bedford County, Pennsylvania. From the TRANSACTIONS of the AMERICAN THE death of young peach trees is principally owing to planting, transplanting, and pruning the same stock, which occasions it to be open and tender, with a rough bark, in consequence of which insects lodge and breed in it, and birds search after them, whereby wounds are made, the gum exudes, and in a few years the tree is useless. To prevent this, transplant your trees as young as possible, if in the kernel it will be best, as there will then be no check of growth. Plant them sixteen feet apart. Plow and harrow between them, for two years, without regard to wounding them, but avoid tearing them up by the roots. In the month of March or April, in the third year after transplanting, cut them all off by the ground, plow and harrow among them as before, but with great care, to avoid wounding or tearing them. Suffer all the sprouts or scions to grow, even if they should amount to half a dozen or more, they become bearing trees almost instantaneously, on account of the strength of the root. Allow no animals but hogs to enter your orchard, for fear of their wounding the shoots, as a substance drains away through the least wound, which is essential to the health of the tree, and the good quality of the fruit. If the old stock is cut away the third year after transplanting, no more shoots will come to maturity than the old stump can support and nourish, the remainder will die before they bear fruit, and may be cut away, taking care not to wound any other stock. The sprouts when loaded loaded with fruit will bend, and rest on the ground in every direction for many years, all of them being rooted as if they had been planted, their stocks remaining tough, and their bark smooth, for twenty years and upwards. If any of the sprouts from the old stump should happen to split off and die, cut them away, they will be supplied from the ground by others, so that you may have trees from the same for 100 years, as I believe. I have now trees from one to thirty-six years old, all from the same stump. Young trees, formed in this manner, will bear fruit the second year; but this fruit will not ripen so early as the fruit on the older trees from the same stump. Three years after the trees are cut off, the shoots will be sufficiently large and bushy to shade the ground so as to prevent the growth of grass, that might injure the trees, therefore ploughing will be useless, and may be injurious by wounding them. It is also unnecessary to manure peach trees, as the fruit of manured trees is always smaller and inferior to that of trees which are not manured. By manuring you make the peach trees larger, and apparently more flourishing, but their fruit will be of a bad kind, looking as green as the leaves, even when ripe, and later than that of trees which have not been manured. Peach trees never require a rich soil, the poorer the soil the better the fruit: a middling soil produces the most bountiful crop. The highest ground is the best for peach trees, and the north side of hills is most desirable, as it retards vegetation, and prevents the destructive effects of late frosts, which occur in the month of April, in Pennsylvania. Convinced, by long experience, of the truth of these observations, the author wishes they may be published for public benefit, and has been informed, that Colonel Luther Martin and another gentleman, in the lower part of Maryland, have adopted a similar plan with great advantage. Method |