THis ingenious and useful inftrument (which tends to reduce the fcience of Plane Trigonometry to an eafy mechani cal operation) derives its principles chiefly from the 2d, 4th, 5th, 6th, and 33d propofitions of the 6th book of Euclid. It is constructed to measure, by inspection only, the length and diameter of any ftanding tree, or bough thereof, with much greater accuracy than heretofore; and thence by the help of tables (annexed to a treatise of its ufes lately published) to give the certain quantity of timber, either in round or fquare measure, with out calculation, or the use of the fliding rule. By this means a criterion is, at length, fixed between the buyer and felJer of an article, which is becoming every day more and more valuable; as either party has it now in his power to prevent error, and to detect impofition.

But although the true measurement of ftanding trees, by a procefs fo extremely fhort and familiar, is no inconfiderable acquifition; yet we perceive, that this inftrument, when fitted to a theodolite, is applicable to more extenfive and important purposes: viz.

For the practical measurement of the heights and distances of objects, acceflible or inacceffible, whether fituated in planes parallel or oblique, to the plane in which the inftrument is placed; for the taking of all angles, whether verti cal, horizontal, or oblique, in any pofition of the planes in which they are formed, whereby the fides and angles of all plane triangles, right-angled or oblique, are determined upon the inftrument, from the ufual data, without any trigonometrical computations; and that, whether level to the line of ftation, ele vated above, or depreffed below the fame, acceffible or inacceffible, upon their own planes, and alfo upon the plane of the horizon. From hence, we apprehend, it will be found very useful in fieldoperations, particularly in the practice of engineering and land-furveying. For by

the method of applying the altimeter, elevation-index, and other moveable parts of the inftrument, the measure of the required fides and angles (right or oblique) is determined to fufficient exactnefs without any computation, or the use of tables, hitherto neceffary to affift the theodolite, and all other graduated inftruments. In it will be found of fingular ufe, as not the practice of engineering, we conceive, only the distance from any fortification,

but alfo, from any visible part or projection thereof, together with the fituation of the plane and place (with respect to the fortification) whereon a battery is proper to be railed, may all be readily obtained, without being under the neceffity, according to the prefent mode of practice, of advancing upon the spot, or of approaching too near the enemy's fire. Then its usefulness in land-furveying, efpecially on hilly ground, is clearly evident; as we obferve, that the perpendicular rife or fall of the land, the hypother ufe, and base-line (neceffary for protraction) are determined at once, upon the instrument, without calculation, and confequently without the risk of error. In fhort, as it appears, that, by this invention, new and very extraordinary acquifitions in fcience are obtained, the measurement of standing trees rendered certain and familiar, the practical operations of engineering, and land-furveying, &c. greatly facilitated, we fincerely with the DENDROMETER may meet with fuccefs equal to its merit and importance.

Reference to the Plate.

A. The femicircle. B. The diameter. C. The altimeter. D. The chord. E. The radius. F. The elevation-index. G. The small femicircle on the altimeter. H. Stays to the altimeter. I. The fcrew to draw the radius backward and forward. K. The flay by which it is confined to the spring-focket. L. The plummet. M. The ftock of the fliding piece. N. The axis. O. The key to move the fcrew of the radius. P. The fliding-piece. Q. The moveable limb of the fliding piece. R. The horizontal index, on which the telescope is fixed. S. Small circular arches to confine the moveable limb of the fliding-piece and the horizontal index in any pofition, &c. T. The fmall quadrant on the horizontal index. Gent. Mag.

SIR,

January 1769.

IT is a common obfervation, but a very just one, that children do not know the duty which is owing to their parents, till they come to have a progeny of their own. Then indeed the numberlels hours of folicitude which they experience for the happiness of their little ones, awake them into the full fenfibility of a filial affection, if they are not wholly callous to the finest feelings of humanity; and they learn a just knowledge of the obligations they lie under to the authors of their being, by the reverence and love which they expect from thofe on whom they have conferred the blefling of existence themselves.

I myself, Sir, am a melancholy proof of the foregoing obfervation. - Mv father, Sir, is a man of family and fortune, who, though he had feveral other children, equally intitled to his attention, yet treated me with fuch an extraordinary fhare of affection, that I was generally distinguished by the name of the favourite. This diftinction, however, instead of giving me a laudable ambition of deferving the parental partiality, filled me only with a fhameful inclination to abufe it; the continual indulgence which fhould excite my gratitude, ferved entirely to fwell my pride; and the favours which I ought to have received with the deepest respect, I looked upon as fo many actual debts to my fuperior accomplishments.-Nay, Sir, I frequently thought my father much obliged to me, when I condefcended to accept a token of his tenderness; and resented as an abfolute indignity to my merit any neceffary document which he gave on the glaring improprieties of my behaviour.

Volatile and vain, my regards were folely centered in myself, and I imagined him either unnatural or kind, as he confulted the gratification of my wishes. Yet though I expected he would upon all occafions comply with the particular turn of my temper, I never recollected that any thing was due to his peace; I never remembered that his happiness materially depended upon my prudence, nor confidered how cruelly an act of difobedience muft ftab him to the heart: on the contrary, Sir, to my everlasting disgrace be it mentioned, I always wanted his repofe facrificed to my own humour, and even found an exquisite pleasure, in revenging on the good, the venerable man, every oppofition which he had made to the arVOL. XXXI.

rogance of my will; that is, in other words, every affectionate anxiety which he manifefted for the advancement of my felicity.

The hand, the upright hand of Heaven, however, has juftly punished my ingratitude, and the very difobedience in which I triumphed, is now, by the wife difpen fation of Providence, a rod of fcorpions to ittelf. If I can, Sir, I fhall purfue my unfortunate ftory: yet the recollec tion of my guilt almoft ftings me into madness; and I even blush to ask compaffion from the world, where I am confcious fo little pity is due to my tears.

Indulged as I was by the goodness thus abuted, Sir, and poffeffed of a perfon, perhaps, palable enough, it may be ea fly fuppofed, that when I approached to maturity, I received fome flattering ad drefles from your fex, especially as I had pretenfions to a genteel fortune. My poor father, indeed, was extremely de Girous of feeing me fettled in the world, and recommended a gentleman to my at tention, who was every way qualified to make me happy, if I had entertained any rational ideas of happiness. But the very argument which fhould have reconciled me to this offer, I mean the recommen❤ dation of a parent, materially determined me against it. I could not bear the thought of being governed: my lover was, befides, a man wholly without fpirit, that is, without either the fashionable follies, or the fafhionable vices of the age; and there was no enduring the lifeless morality of fuch a character: he was, therefore, fpeedily difmiffed; and my father prefuming to be offended at my folly, I complied with the prefling folicitations of a young captain of dragoons, who had newly inrolled himfe!f among the number of my admirers, and fpiritedly accompanied him on a matrimonial tour to Scotland, without ever asking a fingle queftion relative to his circumstances or his family.

Oh! ye amiable, ye now fmiling daughters of Profperity, who enjoy the bleffings of a paternal protection, learn from my wretched fate to fet a just estimation on the tenderness of a father: do not think disobedience a proof of good fenfe, nor imagine it a mark of heroifm to be unaatural. Unacquainted with the ways of the world, you require inftruction from the wife, and none can be so faithful a monitor, as he who is moft deeply interefted in your happiness, Had I pru

dently

dently followed the leffon which fatal experience enables me to inculcate, how many days of anguish had I avoided! But recollection now only ferves to harrow up my bosom, and the mifery which must mark the remnant of my life, is for ever to be aggravated with the confcioufnels of its being justly merited.

. For fome time after my marriage, Sir, I expected every day to receive an overture of reconciliation from my father, and my pride began to be feverely mortified at the bare imagination that it was poffible for him to caft me wholly off from his affection.- But this pride was till more mortified when my husband informed me, that he had loft a large fum of money at play, and that, unless my family immediately did fome very hand fome things for me, he must not only be under an indifpenfable neceffity of felling bis commitlion, but muft eternally bid adien to his country. Thunder-ftruck at this information, I felt all the guilt of my late mifconduct with the keenest Tenability. Nay, my very vanity fup、 plied the place of virtue; and pointed out the meanness of applying only in the hour of diftrefs, and even then of apply. ing merely for relief, to the father whom I had fo infamously deferted, for an acquaintance of a month. However, the application was unavoidable: my hufband's difficulties, if removed, were to be removed inftantly. I therefore fat down blufhing with fhame, yet trembling with apprehenfion, and wrote a peniten. tial letter to my father, acknowledging my faults, fetting forth my diftreffes, and conjuring him, by all he held moft dear, to take pity on my wretched fitua

tion.

This letter I dispatched by a footman; who returned in a little time with the excruciating anfwer, that my father had folemnly determined never to hold the Jeaft intercourse with an unnatural wretch who had deftroyed his everlafting peace of mind, and brought an indelible tain upon his boufe, by marrying a depicable gambler. Dreadful as this reply appeared to me, the information it contained, with regard to my husband's character, was the moft infupportable part of it. I always locked upon him to be a gentleman at leaft; though impradently married, I did not fancy myfelf married dilhonourably. But my father's opinion of my choice was unbappily too jufily founded; and when the contemp.

tible fellow, in whofe hands I had placed the whole happiness of my life, difcovered that my expectations of a fortune were entirely at an end, he quitted the kingdom, and the first intelligence I received of his flight, came from a man to whom he had fold, not only the furni ture of his house, but all the little ornaments I carried with me from home, even to the gown in which I was then dreffed; leaving me but two guineas, to enter upon an inhospitable world, and to fupport a helpless poor infant, who was as cruelly deferted as its unfortunate mother.

To whom, or what, or how could I complain?" In the first moments of my diftraction, nothing but the agonizing fondnefs which I felt for my unhappy little boy, prevented me from fome a& of defperation on my own perfon. When I confidered the miserable state to which I had reduced myself, my mind was hurried into madness; but when I faw my fweet innocent, and recollected his life immediately depended upon mine, my defpair was melted into anguilh, and found relief in a plentiful flood of tears, With the two guineas already mentioned, and a few finall fums which I have borrowed from the friends who still condefcended to own me, I have made a fhift, Sir, to subsist for a twelvemonth, which has now just elapfed fince the flight of my barbarous husband. But, alas! Sir thefe refources now begin to fail me. People induftrioufly feek caufes to avoid an intercourfe with the wretched, and I who once thought it difgraceful even to make conceffions to a father, am now obliged to fupplicate the compaffion of ftrangers for a precarious bit of bread. What will become of me, Heaven only knows! unless I am speedily affifted. My beautiful prattler lies at this moment dangerously ill of a fever, and must inevitably perifh for neceffaries, if the miniftering angel of Providence does not quickly ftretch forth fome blessed hand to his relief.

To my father I dare not look up for pity. Yet, venerable author of my being! if you could conceive but the finalleft idea of what your abandoned Maria feels for her disobedience, if you could but know the pangs which tear her bofom, while fhe thus relates her ingratitude to you, and weeps upon the melancholy cradle of her expiring infant, your generous heart would be truck at

her