Abbildungen der Seite

would overwhelm the parent, wife, and children of this friend, should he fight and die, our author adds,

• Independently, however, of these considerations, remember you are a Christian ; that is to say, a disciple of him who has made the forgiveness of injuries (great as well as little,) for there is no distinction, the characteristic of those who belong to him, and who, to confirm his doctrine by his exampie, died praying for the wretches who were shedding his blood.' p. 48.

To adnit the claim of this person to the denomination of a' Christian,' a disciple of Christ, while expressly charging him with this most criminal disposition,' is a credulity titly rewarded by that privilege from the jurisdiction of reason

a firm faith in transubstantiation.-By the way, we hope the Doctor's Catholic orthodoxy may not incur any suspicion among his brethren, in consequence of his applying these denominations to a heretic.

A considerable part of the volume is employed in defending some of the popish tenets and institutions, a department of science, vot niuch likely to be ever again in vogue in England. The valuable parts of the book are those which display the most impolitic, and in many points cruel treatment, which the Irish as a nation, and the Irish Catholics in particular, have experienced from the Euglish government. This portion of the book will very much interest every reader who is convinced, as we are, that a different system of policy towards that unhappy country is very fast becoming so imperiously necessary, that to refuse it will be to court destruction.

Anong the questions of Irish antiquity, Dr. M. ably dis. cusses the various opinions advanced concerning the design of the round towers, and proves, we think, that' no conjecture is so probable as that which makes each of them to have been raised for the habitation of a religious recluse. The whole yolume bears evidence of very respectable ability and extensive Jearnirg: Art. V. Philosophical Transactions, of the Royal Society of London for

the Year 1809. Part II. 4to. pp. 280. price 16s. 6d. Nicol, 1809. THIS part of the Transactions of the Royal Society for 1809,

contains eighteen memoirs, numbered from ten to twenty-seven boch inclusive. X. On Platina and Native Palladium from Brasil.

Ву William Hyde Wollaston, M. D. Seç. R. S. Read March 22, 1809.

The mineral, which forms the subject of the present communication, was received lately from the gold inines in Bram

zil, by the Chevalier de Souza Coutinho, ambassador from
the court of Portugal to that of Great Britain. Its general
appearance was such, that Dr. W. could form no opinion of
what it might be found to consist, but it resembled very
closely the form given to platina by attempting to render it
malleable by means of arsenic. It did not appear, however,
to have been subjected to any artificial treatment, as small
particles of gold were distinctly visible on close inspection ;
but it did not exhibit the magnetic iron sand, nor the sinali
hyacinths which Dr. W. had found to form part of the
Peruvian ore. It differed from the cominon ore of platina
in having no polish, the grains resembled the fragments of
a spongy substance, and even those most rounded bad
small spherical protuberances closely coherent, but with
the interstices clean and free from tarnish, A portion of it
was submitted to the action of nitro-muriatic acid; and two
of the grains being observed to be much more rapidly
acted upon than platina usually is, and to give a deeper
red colour to the solution, were separated for subsequent
examination. The other portion, when dissolved and ex-
amined by the usual re-agents, was found to be nearly pure
platina; it contained minute portions of gold and palladium,
but exhibited no distinct appearance of iridiuin or rhodium.
The two grains which had been removed from the former
solution, were dissolved in nitric acid, and a black powder
remained on which the acid exerted no power. The dis-
solved portion was found to be palladium, and another
quantity examined by the action of the blowpipe exhibited
the usual characters of that metal. The black powder dis-
solved readily when a little muriatic acid was added to the
nitric; and from this solution muriat of ammonia threw down
a precipitate of platina coloured by iridium. These, there-
fore, were grains of native palladium ; and on examining its
external appearance, Dr. W. found it easy to distinguish it
from the substances in which it was imbedded. The surface
of the grains was fibrous, with the fibres divergent from one
extremity ; and from the certainty with which he was enabled
to distinguish the grains by this appearance, Dr. W. is induced
to consider it as characteristic.
XI. On a native Arseniate of Lead. By the Rev. William

Gregor. Communicated by Charles Hatchett, Esq. F.R. S.
Read April 13, 1809.

This mineraļ was found in a rich copper mine, in the parish of Gwennap in Cornwall, intermixed with several varieties of the ore of that metal. It is regularly crystallized ; and the form of its most perfect crystal is a hexaedral prism, varying in diameter from the tenth of an inch to the

[ocr errors]

thickness of a hair. The longest crystals do not exceed to of an inch ; and these terminate in a plane at right angles to the axis of the prism, but many of the smaller ones terminate in a fine taper point, which Mr. G, suspects to be a sixsided pyramid. The colour varies from the yellow of the Brazilian topaz, to the brown of common resin, or coarse sugar-candy. Some of the crystals are perfectly transparent, and the angular fragments of these are sufficiently hard to scratch glass; the external lustre is in some specimens vitreous, in others resinous, and occasionally the surface is covered with delicate filaments of a silkylustre. "The specific gravity of the purest crystals is 6.41 at the temperature of 50°. A portion, melted in a gold spoon by the blow-pipe, did not appear to be altered when kept in a state of ignition ;

but when heated on charcoal it was speedily decomposed, arse, nical vapours were disengaged, and metallic lead' remained behind. It is soluble in nitric acid, even without beat, if reduced previously to a state of powder. The transparency

of the solution is not diminished by nitrat of barytes ; nitrat of silver renders it turbid, and sulphuric acid and its soluble compounds produce a copious precipitate of a heavy white powder. The liquid, after the precipitates have subsided, when cleared from the superabundant sulphuric acid, yields an abundant white precipitate on the addition of nitrat of lead in solution, and this precipitate, when acted upon by the blow, pipe in contact with charcoal, resolves itself into metallic lead and arsenical vapours.

These facts led Mr. Gregor to conclude that the mineral consisted of oxide of lead, arsenic acid, and a small portion of muriatic acid; and from more ample and accurate analysis of which a detail is given, he estimates its composition at oxide of lead, 69.76. arsenic acid 26.40. muriatic acid 1.58. with small portions of silica and oxide of iron, which appear to be merely accidental ingredients. XII. An anatomical Account of the Squalus maximus (of Lin

neus) which in the Structure of its Stomach forms an intermediate Link in the Gradation of Animals between the IVhule-Tribe and cartilaginons Fishes. By Everard Home, Esq. F. R. S. Read May 11, 1809.

In a former paper, inserted in the first part of the present volume, Mr. H. gave an account of the peculiarities in the formation of the spine of the squalus maximus ; and in this he describes other remarkable features in its anatomical structure. The fish, from which the account is taken, was entangled in the herring-nets off the coast of Hastings in November 1808: it measured 36 feet 6 inches in length, and about 9 feet from the extreme point of the dorsal fin to the middle line of the abdomen. The structure of the stomach is the most remarkable circumstance in the description here given ; and in this respect it is so essentially diferent from the shark, that Mr. H. considers it as forming an intermediate link between the shark and the whale. “ Besides the cardiac and pyloric portions, as in other sharks, there is a globular cavity, with which the pyloric portion communicates by a very small orifice, and there is another orifice nearly of the same size, between this cavity and the intestine. The upper part of the duodenum is smooth, and the gall ducts open into it by a long nipple-like projection, and just below this the spiral valse has its origin as in other sharks." p. 210.

Mr. H. is of opinion, that the shark tribe, from the peculiarities of internal structure, may be sub-divided into many genera, making, with the rays and skates, so many links between the whales, and fishes properly so called. It is not unworthy of notice that two other squali of large dimensions were thrown upon the coast about the same period; one at Penrhyn in Cornwall, the other at Stronsay one of the Orkneys. The last was in an almost putrid state, and much mutilated when first observed; and our readers will probably recollect that it was described with much minuteness of detail in the journals of the day, as a new species of sea snake. The depositions on the subject were put into the hands of Mr. Home by. Sir Joseph Banks, and he procured portions of its skull, spine, and cartilages through the intervention of his friend Mr. Laing, and on comparing these with the corresponding parts of the squalus maximus, they were found to agree both in form and diinensions. This paper is illustrated by four engravings, exbibiting the natural figure and proportions of the fish, and the structure of its stomach compared with that of the common dog-fish. XIII. On an Improvement in the Manner of dividing astrono

mical Instruments. By Henry Cavendish, Esq. F. R. S. Read May 18, 1809.

The accurate division of astronomical instruments is of such great importance, that every suggestion for its improvement merits attention. The plan proposed by Mr. C. is to use a beam compass with only one point; and to substitute, for the other, a microscope movable from one end of the beam to the other. The compass is to have its centre of motion on a frame resting steadily on the face of the circle to be divided, and fixed so as to be capable of sliding round it by means of an adjusting motion, that may admit of its being brought to any required point. The centre of

[ocr errors][ocr errors]

236 Philosophical Transactions, for 1809. Part II. motion of the compass itself is also movable, so as to admit of adjustment to circles of different magnitudes. The plan is at once simple and ingenious, and appears to be capable of a very considerable degree of accuracy; but its real value, Mr. C. justly observes, must be determined by experience, and the judgement of artists. The requisite apparatus is much less complicated than in the mode adopted by , Mr. Troughton, and described in the former part of the present volume; and it does not require the computation of a table of errors, and the subsequent adjustment of a sector according to the numbers of that table, both of which are indispensable in Mr. Troughton's method. XIV. On a Method of examining the Divisions of astronomi

cal Instruments. By the Rev. William Lax, 4. M. F. R. S. Lowndes's Professor of Astronomy in the University of Cambridge. In a letter to the Rev. Dr. Maskelyne, F. R. S. Astronomer Royal. Read June 1, 1809.

This is a valuable communication, but not very susceptible of abridgement. By means of a simple apparatus which he has described with sufficient minuteness, Mr. Lax measures the subdivisions of the instrument to be examined, beginning with the arc of 180°, and proceeding afterwards to those of 90°, 60°, 45°, &c. and measuring each succeeding arc of the same magnitude in the circle, against that first ascertained, and noting down their differences with the characters + or prefixed. This measurement determines the proportion which the first, and each succeeding arc, bears to the whole circle, and consequently the absolute lengths of the arcs themselves.

“Let a denote the real length of the first of these, and +a', t- a", + a", &c. the difference betwixt the first and second, the first and third, &c. respectively; let A represent any other arc whose length is known, and wbich is a inultiple of a, as marked upon the instrument, and let this multiple be expressed by 11. Then will a+ (ata') + (a+a'l) + (a+a")+&c.•(a ta'"...»~1) A, and a=Ad-all-a!!

.. Hence it is evident, if there is no error committed in the measurement of any of these arcs, we shall have the value of

a, and consequently of ata', ata'', ata", &c, and of any arc, comprehending any number of these accurately determined." p. 235.

The plan is not liable to any considerable degree of error, but it must of course vary in some measure with the accuracy of the examiner's eye, and the excellence of the microscope employed. The apparatus here described has also the advantage of supplying a ready mode of rectifying observa


« ZurückWeiter »