« ПретходнаНастави »
branches of the same tree that were abroad, the blofsoms were but just beginning to thew themselves. In short, none of these internal branches appeared to be in the least degree affected by the frost-nipt state of their trunks; but were as forward, as if the intire trees or shrubs had been in the hot-house.
The result will easily be conjectured of the converse of this experiment. The trees, &c. that were placed in the inside of the hot house, had their branches covered with leaves and flowers about the middle of May; while the single branch of each that was carried to the outside, was absolutely at this time in the very same state with those that grew abroad, exhibiting the same appearances that trees present during the winter, and deriving no advantages from the warm situation of their respective trunks and branches within the hot-house.
It seems evidently to follow from these experiments, that there is no regular or general circulation of the fap in trees between the trunk and the branches ; as these lait, which were admitted into the hot-house, vegetated vigorously, while their trunks and their other branches were in a ftate of torpidity of inaction, and covered with ice. They likewise prove, that each part of a tree is furnished with a quantity of fap, independent of any fupply from the trunk or other branches, fufficient to effect the first production of buds, flowers, and fruits, provided that these juices are put into motion by heat.
An accident that attended the Author's course of experi. monts, suggests a useful improvement in the treatment of fruit trees. A fuail having gnawed and destroyed the petals, and the Romina, or male flowers, of three of the flower buds of one of his apple trees, but without hurting the piftillum, he was sure prized to find that they produced fruit, while the greater part of the other flowers, which had not been injured, did not bear
Taking a hint from the fnail, the Author cut with his fcisfars the petals of different apple, pear, plum, and cherry blossoms, close to the calyx. Almost every one of the flowers, thus treated, bore fruit; while several of the neighbouring flowers miscarried. It will naturally be supposed that the destruction of the stamina would render the fruio barren, or that it would want those seeds that contain the germen that is to perpetuate the species. Accordingly, in cutting open the apples whose petals and stamina were eat up by the snail, he found the capsule formed as usual at the center of them; yet they were entirely empty, without the least appearance of a pip.!
In the 12th Article are contained some circumstances communicated by Dr. Ducarel, relating to the early cultivation of botany in England; and particularly concerning the celebrated John Tradescant, a great promoter of that science, as well as of natusal history, in the last century. In the 22d article is given a description and delineation of a rare American plant of the • Brownææ kind,' by M.P.J. Bergius. Article 5th contains the catalogue of 50 plants presented annually to the Royal Society by the company of Apothecaries.
NATURAL HISTORY, In the 2d Article, Mr. Adam Walker briefly describes the petrefactions and other natural curiofities of the cavern of Dunmore Park, near Kilkenny in Ireland. In the 3d, Dr. Michael Morris gives a short account of some specimens of lead ore, containing native lead, found in a mine in Monmouthshire. The 19th Article is a table conftructed by Dr. William Withering, ascertaining the principles of twelve different kinds of marle found in Staffordshire: And in the 21st Article, the Hon. Daines Barrington describes a foslil lately found near ChristChurch in Hampshire.
Papers relating to ELECTRICITY and METEORS. The 6th Article is a short extract of a letter from Mr. Kinnerfley to Dr. Franklin ; in which after taking notice of the remarkable conducting quality of some kinds of charcoal, and observing that a strong line drawn on paper with a black-lead pencil
will conduct an electrical shock pretty readily, he mentions the effects of a late thunder storm in Philadelphia. A floop and three houses were, in less than an hour's time, all ftruck by it. The floop, and two of the houses, were considerably damaged ; but the third, which was provided with a cylindrical iron conductor, only half an inch thick, confisting of an assemblage of several rods strongly screwed together, the least of which was funk 5 or 6 feet under ground, was preserved from all kind of injury, by means of the apparatus'; which had evidently sustained the shock, and conducted the lightning, with no other injury to itself than the melting of 6 inches and a half of the slenderest part of a brass wire fixed on the top of it. Captain Falconer was in the house during the accideot, and observed the explosion to be an astonishing loud one.' Article 8. A Report of the Committee appointed by the Royal Society,
to consider of a method for securing the Powder Magazines at
Purfleet. Article 9. Obfervations upon Lightning, &c. By Benjamin
Wilson, F.R.S. &c. Article 10. A Letter to Sir John Pringle, Pr. R. S. on pointed
Conductors. We have already given the substance of some of Mr. Wilson's objections, offered in the gth Article, to the report which forms the subject of the 8th, and to a part of which he had formally expressed his diffent in writing. (See our Review for last Month, page 386.] These objections having been maturely considered by the committee, they, in the roth article, declare that they still find no reason to change their opinion, or to vary from their former report in favour of pointed conductors. The subscribing members of this committee are the Hon. Mr. Cavendith, Dr. Watson, Dr. Franklin, and Mr. J. Robertson. Article 20. ' An Account of a fiery Meteor seen on February 10,
1772,' near Berwick; and of some new ele&trical Experiments By Patrick Brydone, Esq;
Whether all the meteors that have been described and re. corded in the Philosophical Transactions have had any just pretensions to a place in that respectable collection, may perhaps be doubted. The present, however, seems justly intitled to that rank, as well on account of its splendour and duration, as of its height; and still more on account of the data from wbich that height may be estimated. It appeared in the form of a fplendid Aame of a conical figure, the light of which almost ex. tinguished that of the moon, then about half full; moving nearly horizontally through a space of about 30 degrees, at about the height of so degrees, and seemed to burst at the end of 10 or 12 seconds into a number of sparks, resembling the stars in a sky-rocket.
The Author expecting a report, had the presence of mind to take out his watch, which had a second hand; but after stopping above 4 minutes without hearing any, he rode on. In about a minute afterwards, however, he was stunned by a loud and heavy explosion, resembling the discharge of a large mortar at no great distance, and followed by a kind of rumbling noise like that of thunder.' On examining his watch, he found that the found had taken 5 minutes and about 7 seconds to reach him; which, according to the common computation of 1142 feet in a second, gives a distance of at least 66 miles. At a place distant about 20 miles West, this meteor, the appearance of which was likewise followed by a loud report, was seen by two gentlemen, nearly at the same height as it was per ceived by Mr. Brydone : so that its distance from the earth was probably greater than the sensible limits of our atmosphere, This phenomenon, we shall observe, as well as many others, furnishes a strong presumption that the air is not the only medium of found : as the violent report occafioned by it originated probably in a region, where there was as near an approach to a vacuum as any that we can make with our best air pumps.
In the remaining part of this article, the Author relates fome experiments in which he charged an insulated conductor, by rubbing the back of a cat. The animal, however, not patiently submitting to the experiment, the farra effects were produced on a young lady's combing the hair of her fifter's head, which, however, we mould observe, had not, like the hair of most other young ladies, been matted together and defiled by a paste of pomatum and powder. On causing the pointed wire of a coated vial to follow the comb, the vial was highly charged, so as to give a smart shock, and set fire to spirits.
In these experiments, the Author's disposition of the two ladies does not appear to us to have been perfectly scientific. The lady who performed the office of the rubber, ought not to have stood on wax; unless indeed to Thew occasionally that she likewise became electrified, but with a contrary electricity, on the approach of any body communicating with the earth : and the lady whose hair was combed jould have been insulated, in order to produce the greatest effect.
In the 23d Article is given an account of some of the effects of a thunder storm, in which Mr. Heartly was killed in his bed. Mrs. Heartly, who lay on his left hand, was awakened by the explofion, and found her right arm stunned and benumbed, and a little painful. Not being alarmed, however, she fell alleep, and did not discover, till she awoke in the morning, that her husband had been killed by it. Though the bed post was split into many shivers, one of which was found within his nightcap, no marks were discovered on any part of his body; except that his right cheek was swelled, and his hair on that side considerably singed, as was the inside of his nightcap on the same fide, while no such marks appeared on its outside.
The 13th Article contains only some thermometrical observations relating to remarkable degrees of cold observed on the Continent in 1767, 1768, and 1770, by M. J. H. Van Swinden.
Tinfoil, with the Salt composed of Copper and the niticus Acid.
Before we give the substance of this curious experiment, it will be proper to premise a discovery of the Author's, relating to the metallic salt produced by a combination of the nitrous acid with copper ; which he found to possess the peculiar property of taking fire, and deflagrating in a degree of heat not greater than can be borne by the hand. This quality is most conveniently thewn by twice or thrice dipping a piece of soft bibulous paper into a saturated solution of copper in spirit of nitre, and alternately drying it with a gentle heat. If the paper, thus copiously impregnated with the cupreous salt, be then held at a moderate distance from the fire, it will delagrate and burn to a brown calx.
The success of the following experiment depends on the ready accensibility of this metallic salt. A fufficient quantity of it in a somewhat moist state, procured by putting several pieces of thin sheet copper into a weakened Tpirit of nitre, is to be beaten to the fineness of basket fea fali, and strewed to the
thickness of a shilling on a piece of 'tinfoil, twelve inches in length, and three in breadth. The foil is then to be instantly rolled up, so as to include the falt, as it lies, between the coils. The ends being pinched together, and the whole pressed flat and close, the following phenomena successively present themselves.
First, a part of the fale deliquesces, and, being imprègnated with the tin, a frothing is perceived at the ends of the coil, attended with a moderate warmth, and followed by a copious emision of nitrous fumes. The heat then increafes fo as to become intolerable to the fingers; and, at length, explosion and fire are perceived, which burst and melt the tinfoil, if it be very thin. Those who would repeat the experiment must consult the Author's own account of it, as the success in a great measure depends on an attention to some minute circumstances which we have not room to mention.
The Author's rationale of this process is principally founded on the abovementioned property of the cupreo-nitrous falt, or on its easy ignition in a slight degree of heat. Its acid is fupe posed in part to quit the copper, and to attack the tin *; in its commenstruation with which metal, a considerable effervefcence and heat are produced, sufficient to dry the remaining undecompounded cupreous sa't, and to set it on fire. The ignition may likewise, we imagine, be in some meafure the consequence of a niirous sulphur extemporaneously formed, by the rapid combination of the nitrous acid with the phlogiston of the tin, and which is instantaneously kindled and dissipated in the very act of its formation,
ANTIQUITIES. Article 4. Farther Remarks upon a Denarius of the Veturiar Family, &c. By the Rev. John Swinton, B. D. F.R.S. &c.
In the 58th volume of the Philosophical Transactions Mr. Swinton informed as that NI. LUFIUS, whose name occurs on this denarius, was probably one of the Italian generals in the Social war. In the present article he haftens to acknowledge and rectify bis mistake, in wrongly decyphering two or three crippled Samnite. Etruscan letters at the tail of the infcription; and now declares his opinion that this suppoled old soldier was really the Merriss, Merrix, or Meddix, or at least one of the
And yet the nitrous acid has a lefs degree of affinity to tin than to copper, the latter of which it dissolves, while it only corrodes the former ; perfectly dephlogisticating it, or reducing it to a compleat calx. Its violent action on the tin therefore, though already saturated with the copper, is, we apprehend, to be attributed to this circumstance; that though it has a very inconsiderable degree of affinity to the metallic earth of the tin, it attacks this metal with violence on account of its very strong attraction of phlogistori; a principle which is known to adhere to tin very laxly.