years, as fome of the former years of fearcity would come into that period; but the 8 years immediately following, that is, from 1685 to 1691, both included, give an average price of no more than 11. 175. 12d. The difference, which is as full 5 to 4, is well deferving our notice. "A third but very short period is from the year 1686 to 1688, in which time Cathini could find no spot in the Sun. If both years he included, we have the average price of wheat, for those three years, 11. 158. 03. the quarter. We ought not to compare this price with that of the three preceding years, as two of them belong to the preceding period of scarcity; but the three following years give the average price for the quarter of wheat, il. 128. 103d. or as nearly 11 to 10. The fourth period on record is from the year 1695 to 1700, in which time no fpet could be found in the Sun. This makes a period of 5 years; for, in 1700, the fpots were seen again. The average price of wheat, in thefe years, was 31. 35. d. the quarter. The 5 preceding years, from 1690 to 1694, give 21. gs. 44d. and the 5 following years, from 1700 to 1704, give 11. 175. 11d. These differences are both very confiderable; the last is not lefs than 5 to 3. "The fifth peried extends from 1710 to 1713; but here there was one fpot feen in 1710, none in 1711 and 1712, and again one fpot only in 1713. The acconnt of the average price of wheat, for thefe 4 years, is 21. 178. 48. the quarter. The pre ceding 4 years, from 1706 to 1709, give the price 21. 35. 74d.; and the following years, from 1714 to 1717, it was 21. 6s gd. when the aftronomical account of the Sun for this period, which has been stated above, is confidered, these two differences will be found very confiderable, the fist of them being nearly as 4 to 3. "The refult of this review of the foregoing five periods is, chat, from the price of wheat, it seems probable that fome temporary scarcity or defect of vegetation has generally taken place, when the Sun has been without thofe appearances which we furmife to be fymptoms of a copious emiffron of light and heat. In order, however, to make this an argument in favour of our hypothefis, even if the reality of a defective vegetation of grain were fufficiently established by its enhanced price, it would ftill be neceffary to fhew that a deficiency of the folar beams had been the occafion of it. Now, those who are acquainted with agriculture may remark, that wheat is well known to grow in climates much colder than ours; and that a proper diftribution of rain and dry weather, with many other circumftances which it will not be necefGBNT. MAG. November, 1802. fary to mention, are probably of much greater confequence than the abfolute quantity of light and heat derived from the fun. To this I fhall only fuggeft. by way of anfwer, that thofe very circumftances of proper alternations of rain, dry weather, winds, or whatever elfe may contribute to favour vegetation in this climate, may poffibly depend on a certain quantity of fun-beams, tranfmitted to us at proper times; but this being a point which can only he afcertained by future obfervations, I forbear entering farther into a difcuffion of it." XIV. "Obfervations on the Structure and Mode of Growth of the grinding Teeth of the Wild Boar, and Animal Incognitum" [from the banks of the Ohio]. Defcribes certain particularities lately difcovered with refpect take place during the firft feven years, to the grinders of the wild boar, which and the fucceffion of fuch teeth begrinders confift of 16, 4 on each fide yond that period. The temporary of the upper and lower jaw; fhed in the ufual manner, and their places fupplied by larger teeth, rifing up from the fubfiance of the jaw, immediately under the old ones. Mr. Home proceeds to defcribe the feveral points of fimilarity between the teeth of the elephant, the fus Ethiopicus, and the wild boar; and fubjoins fome obfervations refpecting the form of the teeth, and order of dentition, in other animals, particularly in an unknown animal, whofe teeth have been found on the banks of the river Ohio, in North America. This paper contains feveral curious remarks refpecting the ufual ages, fizes, and other particulars relative to fome other animals. The four wild boar in different fiates of growth, plates reprefent the lower jaw of the and the jaw, teeth, &c. of the abovementioned animal incognitum. XV. "Account of fome Experiments on the Afcent of the Sap in Trees. By Thomas-Andrew Knight, Efq." The refult of Mr. K's nume rous experiments, illuftrated by plates, is, that heat is the remote caufe of the afcent of the fap, and that perhaps frequent variations of it are in fome degree requifite; but that the immediate caufe of that afcent will be found in an intrinfic power of producing motion inherent in vegetable life. The fap is conveyed into the leaf by the bark. The medulla is not neceffary to the progreffion of the fap. The fruit falks falks of the apple, pear, vine, and fome other fruit-trees, are organized nearly like the branch from which they fpring, confifting of the medulla, the central tubes, a very finall portion of wood, the fpiral tubes, and thofe of the bark, and the 12 external fkins; and, in the full grown fruits, the medulla appeared to end in the piftilla. Colouring matter, made ufe of, did not pafs through the fruit-ftalks, but is fuppofed to have returned, by the retrograde motion of the fap, into the tree; and in this channel the fuperfluous humours in the fruit are carried off. The feeds of apples and pears are nourished by a number of minute veffels leading from the pulp to the tubes, which originally conftituted the lower parts of the piftilla, and to which the feeds are attached. It appears not very improbable that the internal organization of this fruit will be found to hear fome refemblance to the placenta and úmbilious cord of the animal economy.A vine, which has grown all Summer under the heat of a flove, will not be made to vegetate during Winter by the heat of that ftove; but, if another plant of the fame variety, which has grown in the open air, be at any time introduced after it has dropped its leaves in the Autumn, it will inftantly vegetate. This effect appears to arife from the latter plant poffeffing a degree of irritability, which has been exhaufted in the former by the heat of the ftove, but which it will acquire again during the Winter, or by being drawn out and expofed, for a fhort time, to the Autumnal froft. On the fame principle we may point out the caufe why feedling plants always thrive better in the Spring than in the Autumn, though the weather be lefs favourable. In the former feafon the ftimulus of heat and light is gradually becoming greater than that to which the plant has been accustomed; in the latter feafon it becomes gradually lefs. If a peach tree be brought into blof fom in one feafon, in the beginning of February, by artificial heat, it will fpontaneously fhew ftrong marks of vegetation at the approach of that feafon in the fucceeding year; and, if it be not well protected, it will expofe its bloffoms to almost inevitable deftruction. This Mr. K. attributes to the accumulated irritability of the plant. "The grain in every kind of wood is of two kinds, the false or baftard, con fifting of concentric circles, which mark the annual increase of the tree, and the true or filver, compofed of thin lamina, diverging, in every direction, from the medulla to the bark, having little adhesion to each other at any time, and lefs during the Spring and Summer than in the Autumn and Winter; whence the greater brittleness of wood in the former feafon. The lamine lie between and prefs on the fap-veffels of the albunun; and every tube is touched by them at fhort dittances, and flightly diverted from its courfe. If there are expansible under changes of temperature, or from any caufe arifing from the powers of vegetative life, I conceive they are as well placed as pollible to propel the fap to the extremities of the branches, and their reftlefs temper, after the tree has ceafed to live, inclines me to believe they are not made to be idle whilst it continues alive. In a perfect quarterboard, into which oak-timber is fawed, the faw exactly follows the directions in which the tree most readily divides when cloven. In this cafe the lamina of the filver grain lie parallel with the furface of the board; and a board thus cut, when properly laid in the floor, is rarely or never feen to deviate from its true horizontal pofition. If, on the contrary, one be fawed across the filver grain, it will, during many years, be incapable of bearing changes of temperature, and of moift, without being warped; nor will the ftrength of numerous nails be fufficient to prevent the inconvenience thence arifing: the furface of a board of this kind, which grew nearest the centre of the tree, will always fhew a tendency to become convex, and the oppofite one concave, if placed in a fituation where both fides are equally expofed to heat and moisture. When an oak has been deprived of its bark, and expofed to fun and air, its furface has been every where covered with fmall clefts. Thefe are always formed by the lamina of the filver grain having parted from each other; and they will long continue to open and clofe again with the changes of the weather. Pieces of oak recently barked were expofed to the fun, but defended from rain. The furface, in a few hours, prefented a great number of fmall clefts, into which I put, in the middle of the day, the points of fmall iron pins. Late in the evening the wood was clofed fo much much as to hold them firmly; and early next morn they were not easily withdrawn; but, as the influence of the fun increafed, the clefts gradually opened, and the pins dropped out. "If the motion I have fuppofed the filver grain to poffefs be more than can be properly adimitted to belong to vegetable life;" Mr. K. refers to the power of moving in the vine-leaf. It is well known that this organ always places itself fo as that the light falls on its upper furface; and, if moved from the place, it will immediately endeavour to regain it; but the extent of the efforts it will make he has not any where feen noticed. He has frequently placed the leaf in fuch a pofition that the fun has fhone ftrongly on its under furface; and he has afterwards attempt ed to put obftacles in its way on which ever fide it attempted to efcape. "In this pofition the leaf has tried almost every method poffible to turn its proper furface to the light; and I have feveral times feen one which, having tried, during feveral days, to approach the light in one direction, and having nearly covered its under furface, by bending its angular points almoft to touch each other, has unfolded itfelf again, and receded farther from the glafs, to approach the light in an oppofite direction. As the whole effect here produced appears to arife merely from the light falling on the under furface, I cannot conceive how the contortions of its ftalk, in every direction, can be accounted for, without admitting, not only that the plant poffeffes an intrinfic power of moving, but that it allo poffelles fome vehicle of irritation; and without this it will be difficult to explain how the heat applied to the branch of the vine within the ftove can put the fap in the roots and external ftem into motion. It may be objected that thefe are always ready when the branch calls for nourish ment, and that they are no way affected by the internal heat. But this cannot be the cafe, becaufe I have found that the ftem fuddenly becomes extremely fufceptible of injury from cold as foon as the branch begins to vegetate, and that its whole powers will be paralyzed for fome days by expofure, for a few hours, to a freezing temperature. Trees have a remarkable power of transferring their fap from one tube to another. The ufe of the medulla 'feems to be to furnish moisture to the rifing leaf, whenever an excess of perfpiration put it in á flate to require it; and accordingly, in the mature annual branches, and thofe of more than one year old, it is dry, and evidently lifelefs. The heart, or coloured wood, diftinguifhed from the alburnum, feems to execute an office fomewhat fimilar to the bone in the animal economy." Mr. K. infers that the fap is not raifed by the fpiral tubes, nor by the central veffels, to which they are appendages. "The common tubes of the alburnum (which do not appear to have been properly distinguished from the central vellels) extend from the points of the annual fhoots to the extremities of the roots; and up thefe tubes the fap moft certainly afcends, impelled by the agency of the filver grain. At the bafe of the buds, and in the foft and fucculent part of the annual fhoot, the alburnum with the filver grain ceafes to act and to exiti; and here, I believe, commences the action of the central veflels, with their appendages, the fpiral tubes. By thefe the fap is carried into the leaves, expofed to the air and light; and here it feems to acquire the power to generate the various inflammable fubfiances that are found in the plant. It appears to be then brought back again, through the veflels of the leaf-ftalk, to the bark, and by that to be conveyed to every part of the tree, to add new matter, and to compofe its various organs for the fucceeding feafon. When I have intentionally fhaded the leates, I have found that the quantity of alburnum depofited has been extremely finall." XVI. 66 Additional Obfervations, tending to inveftigate the Symptoms of the variable Emition of the Light and Heat of the Sun; with Trials to fet afide darkening Glaffes, by tranfinitting the Solar Rays through Liquids; and a few Remarks to remove Objections that might be made against fome of the Arguments contained in a former Paper. By Willian Herfchel." XVII. "On an improved Reflecting Circle. By Jofeph de Mendoza Rios, Efq. F. R. S." XVIII. "Obfervations and Experi ments on Dr. James's Powder; with a Method of preparing, in the humid Way, a fimilar Subftance. By Richard Chenevix, Efq. F. R. S. M. R. I. A." "Dillolve, together or feparately, in the leaft poffible portion of muriatic acid, equal parts of the white oxide of antimony, and of phosphate of line: pour this folution gradually into diftilled water, previously alkalizated by a futficient quantity of ammonia. A white and abundant precipitate will take place, which, well washed and dried, is the fubfiitute propofed for Dr. James's powder, and is more mild, and confequently may be given in larger quantities, feldom producing naufea or vomiting in dofes of less than 8 or 10 graius Dr. Pearfon's analyfis of Dr. James's medicine is in vol. LXXXI. part II. art. XXI. XIX. "Cafe of a young Gentleman who recovered his Sight when Seven Years of Age, after having been deprived of it, by Cataracts, before he was a Year old; with Remarks. By James Ware, Surgeon." The cataract was foft and fluid; and, by puncturing the capfule, the cryftalline was brought into contact with the other humours, a 'confiderable part of it coming forwards, and fhewing itfelf directly under the cornea. In a few days the opaque matter was wholly abforbed, the pupils became clear, and the lad recovered the fight of both his eyes. When children are bora blind with cataracts, Mr. W. obferves, they are never fo totally deprived of fight as not to be able to distinguifh colours; and, though they cannot fee the figure of an object, nor even its colour, unless it be placed within a very short distance, they, neverthelefs, can tell whether, when within this diance, it be brought nearer or carried farther from them; and, in confequence of this power, can immediately, on the recovery of fight, form fome judgement of the diftance, and even of the outline, of fome firongly-defined object, with the colour of which they were previously acquainted. The cryftalline humour has generally, if not always, been found in a foft or fluid ftate: if, in addition to the opacity of the cryftalline humour, its capfule be alfo opaque, and, in confequence of this, the operation abovementioned fhould not prove fuccefsful, which is cafier than extraction, and may be undertaken at an earlier age, it will not preclude the performance of extraction afterwards. XX. "An Account of fome Galvanic Combinations formed by the Arrangement of fingle Metallic Plates and Fluids, analogous to the new Gal vanic Apparatus of Mr. Volta. By Mr. Humphry Davy, Lecturer on Chemistry in the Royal Institution." XXI. "A Continuation [from Phil. Tranf. 1800, p. 161] of the Experiments and Obfervations on the Light which is fpontaneously emitted from various Bodies; with fome Experiments and Obfervations on Solar Light when imbibed by Canton's Phospho rus. By Dr. Nathanael Hulme," XXII. "Experiments on the Chemical Production and Agency of Electricity. By Dr. William Hyde Wol lafton." XXIII. "Farther Obfervations on the Effects which take place from the Destruction of the Membrana Tympani of the Ear; with an Account of an Operation for the Removal of a particular Species of Deafness. By Mr. Ailey Cooper." See before, p. 1029. 214. The Tranfactions of the Royal Irish Academy. Vol. VII. IT is now five years fince we re viewed the preceding volume. The It was published in 1788; II. 1789; III. 1791; IV. 1798; V. 1796; VI. 1797. Of the prefent volume, Art. I. treats" On the Preceffion of the Equinoxes. By the Rev. Dr. Matthew Young, S. T. T. C. D. and M. R. I. A.;" afterwards promoted to the fee of Clonfert and Kilmacdaach, and by whofe death, of a lingering and painful malady, in his 50th year, at Whitworth, in Lancashire, Nov. 28, 1800, Science lost one of its brightest luminaries. See our vol. LXX. p. 1217. "It is univerfally acknowledged that Sir Ifaac Newton has fallen into fome error in his calculation of the fun's force to produce the preceffion of the equinoxes, making it by one half less than the truth; but the particular fource of this error has not been fo generally agreed upon. Mr. Landen first detected the particular fource of Newton's miftake, by difcovering that, when a rigid annulus revolves with two motions, one in its own plane, and the other round one of its diameters, half the motive force acting upon the ring is counteracted by the centrifugal force ariling from the compound notion, and half only is efficacious in accelerating the plane of the annulus round its diâineter. As Mr. L. has not expreflly demonftrated this propofition, I am perfuaded I fhall afford the mathematical reader much gratification gratification by here laying before him the following very elegant demonftration, communicated to me by the learned Mr. Brinkley, profellor of aftronomy in the University of Dublin. A question arifing, If the error of Newton's calculation be as great as is pretended, whence comes it to pafs that the refult of his calculation agrees fo exactly with phænomena; for, on fuppofition that the precellion arifing from the force of the fun alone is but 97, the preceffion caused by the moon will be 40 52 52, and the whole preceffion arifing from both caufes conjoined will be 50 0 19, according to obfervation? To this objection a fatisfactory anfwer is fuggefted by Newton himfelf, where he fays that the preceffion will be diminished if the matter of the earth be rarer at the circumference than at the centre. The reafon of which is evident from what has been already demonftrated; for, the quantity of matter in the earth being given, the distance of the centre of gyration from the centre of the earth will be lefs the more the matter of the earth is accumulated towards the centre, and therefore the lefs will be the angular motion generated by the fun and moon." II. "General Demonftrations of the Theorems for the Sines and Cofines of multiple circular Arcs, and alfo of the Theorems for expreffing the Powers of Sines and Colines by the Sines and Cofines of multiple Arcs. To which is added, a Theorem, by Help whereof the fame Method may be applied to demonftrate the Properties of multiple hyperbolic Areas. By the Rev. John Brinkley, M. A. Andrews Profeffor of Aftronomy." III. "Remarks on the Velocity with which Fluids iffue from Apertures in the Veffels which contain them. By Dr. Matthew Young." It is not the preffure of the circumambient water which accelerates the loweft plate of water, but the preffure of the ambient water which furrounds the cylinder immediately over the aperture; and this lateral preffure, being communicated to the upper furface of the plate, must be as much increafed by the velocity of the fuperior defcending plate, fo as to remain conftantly of the fame magnitude. IV. "A new Method of refolving Cubic Equations. By Thomas Meredith, B. A. Trinity College, Dublin." V. "Of the Force of Teftimony in establishing Facts contrary to Analogy. By Dr. M. Young." The probability of happening is equal to the difference between certainty and the probability of failing, and the probability of failing equal to the difference between certainty and the probability of happening. The probability that a witnefs tells truth in a given inftance will be expreffed by a fraction, whofe numerator is the number of chances for his telling truth, and for his telling falfehood together. The probability that an argument is true, is to be etumated by the ratio for the number of chances for its truth to the number of chances for its truth and falfehood together. It is true, that in neither of thefe latter cafes can we in general determine the actual number of chances; neverthelets, in all cafes where a perlon perceives the probability of an event, he inuft, at the fame time, perceive that there must be fome finite, determinate ratio between the chances for its happening and failing, though he cannot aflign that ratio; for, if there were no finite ratio, either the number of chances for its happening must be infinitely greater or infinitely less than the chances for its failing. In the former cafe the event would appear certain, in the latter, impoffible; therefore, probable in neither.". . . . . "The fources of probability are of two fpecies: the first comprehends thofe probabilities which are derived from confidering the number of caufes that may influence the truth of the propofition; the other is founded folely on experience, whence we conclude that the future will be like the palt, at least we are affured that the fame caufes which produced the paft ftill exist, and are efficient." VI. "On the Number of the primi tive colorific Rays in Solar Light. By Dr. M. Young;" who establishes, by experiments with the folar fpectrum; that there are only three primitive colours, red, blue, and yellow. VII. Obfervations on the Theory of electric Attraction and Repulfion. By the Rev. George Miller, F.T.C.D." VIII. "A general Demonftration of the Property of the Circle difcovered by Mr. Cotes, deduced from the Circle only. By the Rev. J. Brinkley." IX. Additional Obfervations on the Proportion of real Acid in the Three antient, known Mineral Acids, and on the Ingredients in various Neu tral |