« PreviousContinue »
Art. I. Philosophical Transactions of the Royal Society of London. For the Year 1805. Part II. 4to. 176 pp. Nicol. 1805.
TjMFTEEN papers, from the 9th to the 33d inclusively, ■^ form the contents of this second part of the volume of the Philosophical Transactions, for the year 1805.—The subjects of those papers are the following.
IX. Abstract of Observations on a Diurnal Variation of the Barometer between the Tropics. By J. Horjburgh, Esq.
This paper, on the movements of the barometer, is rendered peculiarly interesting from two circumstances; 1st. It contains the result of a barometrical journal, kept at sea, where the barometer has hardly ever been observed with regularity and perseverance. 2dly. It manifests a very re, maskable daily period in the rising and falling of the mercury at sea, but not upon land.
Mr. Horsburgh used two marine barometers of the best
constru£tion. They were situated in the ship's cabin, where
BRIT, CRIT. VOL, XXVIII, JVLY, l8©6.
their basons flood at about thirteen feet above the level of the sea.
"The hours," he fays, "at which the heights of the barometers and thermometers were taken; viz. noon, 4, 10, n, 14, and 19 hours, were chosen, because at these times the mercury in the barometer had been perceived to be regularly stationary between the tropics, by former observations made in India ini8coand 1801. It was found that in settled weather in the Indian seas, from 8 A. M. to noon, the mercury in the barometer was generally stationary, and at the point of greatest elevation; after noon it began to fall, and continued falling till 4 in the afternoon, at which time it arrived at the lowest point ot deprellion. From 4 to 5 P.M. the mercury rose again, and continued rising till about 9 or 10 P. M. at which time it had again acquired its greatest point of elevation, and continued stationary nearly till midnight; after which it began to fall, till at 4 A. M. it«was again as low as it had been at 4 afternoon preceding; but from this time it rose till 7 or 8 o'clock, when it reached the highest point of elevation, and continued stationary till noon."
"Thus was the mercury observed to be subject to a regular elevation and depression twice in every 24 hours in settled weather; and the lowest station was observed to be at about 4 o'clock in the morning and evening. I remarked that the mercury never remained long fixed at this low station, but had a regular tendency to rife from thence till towards 8 in the morning, ajid about 9 in the evening, and from those times continued stationary till noon and midnight.
"In unsettled blowing weather, especially at Bombay during the rains, these regular ebbings and flowing of the mercury couldriot be perceived; but a tendency to them was at sometimes observable when the weather was more settled." P. 178.
It appears likewise, from the observations mentioned in this paper, that the abovementioned periodical movements of the mercury in the barometer, are observable in the torrid zone, and as tar as a few degrees beyond the tropics. Alfo'ibat those periodical movements take place at sea, but not upon kind, as Mr. H. particularly remarked in those parti-of India and China where he had the opportunity of landing.
X. Concerning the Differences in the Magnetic Needle, on Board the Investigator, arising from an Alteration in the Direclitn of the Ship's Hind. By Matthew Flinders, Esq. Com-< mander ps His Majesty's Ship Investigator.
• Cafptain Flinders, being employed in surveying along the south coast of New Holland, observed a very remarkable
■i irregularity irregularity in the magnetic needle; namely, that the direction of the needle was not the lame, when the ship's head was turned one way, as when it was turned the contrary way. He took every precaution to remove whatever appeared capable of influencing the motion of the needle; but all in vain; for the needle's direction continued to vary according as the ship's direction was changed; and the difference, in some cafes, amounted to about four degrees.
The paper contains tables of his various observations; from which this author deduces the following inferences.
"ist. That there was a difference in rhe direction of the magnetic noedie oh board the Investigator, when the ship's head pointed to the cast, and when it was directed westward. 2d. That this difference was easterly when the stiip's head was west, and westerly when it wns east. 3d. Thtt when the ship's head Was noi :h or south, the needle took the fame direction, or nearly so, that it would on shore; and showed a variation from the true meridian, which Wis ncarjy the medium between what it showed when east and when weft. 4th. That the error in variation was nearly proportionate to the number of points which the ship's head was from the north or south." P. 191.
This author then, with much propriety and diffidence, proposes the following conjectures in explanation of those phenomena.
"ist. I suppose the attractive power of the different bodies in a ship, which are capable of affecting the compass, to be collected into something like a focal point or centre of gravity, and that this point is nearly in the centre of the ship where the shot are deposited, for here the greatest quantity of iron is collected together. 2d. I suppose this point to be endued with the fame kind of attraction as the pole of the hemisphere where the ship is; consequently, in New Holland, the south end of the needle would be attracted by it, and the north end repelled. 3d. That the attractive power of this point is sufficiently strong in a ship of war to interfere with the action of the magnetic poles upon a com-* pass placed upon dr in the binnacle." Ib,
The latter part of' the paper contains some observations concerning the influence which Pier Head, upon the coast of New Holland, has upon the magnetic needle.
XI. The Pfcfiohgy of the Stapes, one of the Bones of the Organ of Hearing; deduced from a comparative Vietv of its Struclure, and U/es, in different Animals. Bv Anthony Car. lisle, Esq. F.R.S.
A 8 The
The principal object of this paper is to give a more accurate description than had been before given, of that bone belonging to the organ of hearing, which has been denominated Jtapcs, staff a, ffapha, or Jtapeda.
Mr. C. justly observes, that, as the accurate anatomical descriptions of the eye, which have been furnished by the ingenuity of professional persons, have contributed to the advancement of optics; so it may be reasonably expected, that a thorough examination of the structure of the organ of hearing will improve the subject of acoustics for the benefit of the human species.
Alter a general, but concise, description of the principal parts belonging to the organ of hearing, this author gives a very particular and accurate description of the human stapes, with its various measurements, and its usual weight; and describes likewise the structure of the same bone in various other animals. A plate, which accompanies this paper, exhibits various views of the human stapes, and the stapes of the hedge-hog, of the mole, of the musk ox, of the elephant, of the tiger, of the dog, and of several other animals.
These descriptions are accompanied with several judicious remarks, respecting the peculiar dispositions of the abovementioned animals, the different acuteness of their hearing, the different elements they live in, &c.
"In man," Mr. C. fays, "and the most numerous orders of the mammalia, the figure or the stapes is an accommodation to that degree of lightness, which, throughout the series of ossicles seems a requisite condition. It is also a conductor of vibrations in common with the other ossicles: but most especially it is designed to press on the fluid contained in the labyrinth by that action which it receives from the stapedeus muscle, and the hingelike connection of the straight side of its basis with the fenestra vestibuli; the ultimate effect of which is an increase of the tension of the membrane closing the fenestra cochlea;.
"It does not appear that any degree of motion ever subsists between the oflicula auditus as wholes, which bears any relation to the peculiar vibrations of sounds; but rather, that the different motions of these bones only affect the membrana tympani, and alter the degrees of contact in their articulations, so as to influence the intensity of violent impulses; sounds of less impetus, not requiring such modulation, are transmitted through the conducting series by the vibrations of the integrant parts of these bones, unaccompanied by muscular action.
"This reasoning is suggested by the columellæ in the aves and auphibia: and as many birds are known to imitate a variety of artificial sounds with great accuracy, it may be inferred that
they they hear such sounds as acutely, and with the fame distinctness as mankind.
"It seems that all the muscles of the officula auditus are of the involuntary kind, and the peculiar stimulus to their action is found. The chorda tympani, which supplies them, is a gangliated nerve: if this supposition be true, then the muscles sliould be considered as all acting together, and it is well known that persons who hear imperfectly are more sensible to sounds in a noisy place, as if the muscles were, by that means, awakened to action.
"The office which the basis of the stapes holds, and which the stapedeous muscle is especially destined to perform, seems to throw considerable light on the use of the cochlea. It cannot be allowed that the pressure of the watery fluid in the labyrinth is a requisite condition to produce the sensation of hearing, since all birds hear without any mechanism for that purpose, but as such pressure must ultimately give increased tension to the senestra cochlea, it follows that we inquire, at this part, for the principal use of the stapes.
"As the membrane of the senestra cochlcæ is exposed to the air contained within the cavity of the tympanum, it appear* adapted to receive such sounds as pass through the memorana tympani, without exciting consonant motions in the series of officula auditus." P. 206.
XII. On an artificial Subpance which possesses the principal characlerijlic Properties of Tannin. By Charles Hatchett, Esq.
This paper commences with a concise history of the original discovery of the tanning principle, and of the subsequent observations made by various ingenious persons, relative to its origin, its properties, its existence in the various vegetables, which arc, on that account, subservient to the tanner, &c. This author then fays, that in the course of his experiments, he was convinced that a substance possessing the chief characteristic properties of tannin, m.iy be easily formed, not only from vegetable, but even from mineral and from anim.il substances. He describes the ex■periments he made under the influence of that conviction, in consequence of which he discovered an artificial method of forming a substance capable of precipitating glue from its solution in water, and of tanning leather. The fact in ihort is "that a substance, very analogous to tannin, which has hitherto been considered as one ot the proximate principles of vegetables, may at any time be produced, by ex
A S poling