Chapter X: Part 10

It will be better to leave a little of the spirit above the mercury in the longest leg; in which case the top of the spirit will shew the common degrees of heat. For the filling the tube, so as to leave none, is attended with some trouble; and more of it will be apt to get up there, if the instrument should happen to be held in an improper situation, or if it be kept in too warm a place without filling the shorter leg with mercury by the method above described. If too great a quantity should get up, tho’ it would not affect the scale for the common degrees of heat, it would however cause some error in the degrees on the shorter leg; inasmuch as the expansion of that portion of spirits, which has got up into the longer leg, exceeds the expansion of the mercury, which must supply its place. It may be got back at pleasure, by exposing the thermometer to such a degree of cold as will make the spirit get beyond the bend of the syphon; for then it will run up along the thread of glass in the shorter leg till it gets above the mercury there. For this purpose the point of 0 degrees of Fahrenheit’s scale should be near the bend; by which means, any part of the spirit of wine may be got beyond it by an artificial cold; and there will be no danger of the whole getting beyond it by any natural cold; in which case the air would get up into the ball.

The scale of degrees on the shorter leg will, in different seasons, be liable to an error of the same kind as that, which was explained in the first-mentioned thermometer; but in this it will be less considerable, as the space between the two scales is filled with mercury, whose expansion is about six times less than that of spirit of wine.

In the thermometer, which I have, the bore of the tube is about 0.054 inches; and one inch of it contains eight grains of mercury, and answers to seven degrees of Fahrenheit’s scale. The drops of mercury, which fall into the ball A, answer to about one eighth of a degree.

If instruments of the nature of those above described, were to be used for finding the temper of the sea at great depths, some alteration would be necessary in the construction of them, principally upon account of the great pressure of the water; the ill effect of which can, I believe, be prevented no other way, than by leaving the tube open. For if the thermometer was made strong enough to resist the pressure without breaking, yet it would be impossible to be sure, that the figure of the glass would not thereby be altered, which should make the experiment uncertain.

The instrument for finding the greatest heat might be made just like that of fig. 1. only leaving the top open. It is to be filled with mercury only, as is also the lower part of the ball at top, but not near so high as the end of the capillary tube. The upper part of that ball, being left open, will in a great measure be filled with the sea-water, which will be forced into it by the pressure.

If this instrument (the tube being quite full of mercury) is plunged into any part of the sea, where the heat is greater than that of the air above, part of the mercury will be driven out of the tube; and, upon bringing it into a colder place, the sea-water or air in the ball will enter into the tube, and will fill the space left by the mercury.

As this thermometer does not show the common degrees of heat, it must be placed in a vessel of water with another thermometer, and the scale of degrees at top will shew how much the heat it has been exposed to is greater than that of the water in the vessel.

The sea-water getting into the glass will corrode the mercury, and thereby foul the glass; which will make the experiment less exact: and therefore it would be much more convenient, if the sea-water could intirely be kept out; which probably may be done by tying a bladder full of air to the neck of the ball C, which will contract by the pressure of the water, without letting any of it get in.

If this can be done, the instrument may be filled with mercury and spirits, just like that at fig. 1. But it would be more convenient to fill it with mercury only: in which case it may be made with as small a tube and ball as common mercurial thermometers: or it may be filled with spirits only. The instrument will thereby become much less bulky; which will compensate the want of the common scale of heat.

It is better to put but little mercury into the ball at top, for fear of its getting into the capillary tube by the motion of the instrument.

The thermometer for finding the greatest cold, if applied to this purpose, must also be left open at top. There is another inconvenience to be avoided; which is, that the mercury in the ball A, by the tossing of the instrument, might sometimes get into the shorter leg of the syphon; which would spoil the experiment. To prevent such an accident, the most convenient construction, which occurs to me, is that of fig. 4. which differs from fig. 3. in having the ball A omitted; so that the mercury running out of the shorter leg will fall to the bottom of the cylinder, and will not be so liable to get back into the tube by motion. The cylinder is made to stand not quite parallel to the legs of the syphon, that the mercury contained therein may more easily be brought to touch the end of the tube, in order to fit the instrument for a new experiment.

If, by means of a bladder, the sea-water can be kept out of the glass, this instrument may be made to shew the common degrees of heat; but even then, in order to render it less bulky, it may be better to supply the want of them as in the last instrument. The longer leg of the syphon may in that case be made as short as you please; only making the ball B big enough to receive all the mercury, which may be driven into it by heat.

If thermometers of this kind were to be sent up into the air by means of a kite, they might be made like those proposed for the sea; but it would not be necessary to leave them open.

As it would be desirable to make them as small as possible, they should be made so as not to shew the common degrees of heat: and it would also, on that account, be convenient to omit the thread of glass placed within the shorter leg of the syphon in fig. 3. and 4. This thread of glass is placed there in order to make the mercury fall into the ball A. fig. 3. or cylinder C. fig. 4. in smaller drops, and also to facilitate the filling the shorter leg with mercury. The latter purpose may be answered by having a ball blown towards the bottom of the shorter leg, as marked in fig. 4. at M: for as soon as the mercury driven out of the cylinder by heat gets to that ball, it will pass by the spirit of wine. The other purpose may probably be answered by having the tube contracted as much as possible at _n_.

In the foregoing instruments the tubes made use of were of a large bore, as most of the errors in them would increase by making use of smaller ones. Possibly less ones might be used without much inconvenience. The chief advantage will be, the making these thermometers more sensible of the changes of heat, than when large cylinders are used. This will be of service when the greatest degree of heat or cold continues but a short time.

It is better to use plain spirit of wine, than what is tinged, which seems more apt to cause a foulness in the tube, and thereby makes the surface of the mercury less well defined. I am induced to believe so, from observing, that the portion of spirits above the mercury in the tube fig. 3. which at first was strongly tinged with cochineal, in some months became perfectly colourless, the tinging particles being deposited in different parts of the tube, and causing a foulness there. The colour of the spirits in the cylinder does not appear to be altered.

The dark-shaded part in the several figures represents mercury, the dotted part spirit of wine.

_J. Mynde sc._]

XXXIX. _Observationes Anatomico-Medicæ, de Monstro bicorporeo Virgineo A. 1701. die 26 Oct. in_ Pannonia, _infra_ Comaromium, _in Possessione_ Szony, _quondam Quiritum_ Bregetione, _in lucem edito, atque A. 1723. die_ 23 Febr. Posonii _in Cœnobio Monialium_ S. Ursulæ _morte functo ibidemque sepulto. Authore_ Justo Johanne Torkos, _M.D. Soc. Regalis Socio._

[_See_ TAB. XII.]

[Read May 23. 1751.]

I. PARTUS hic bicorporeus singulare exemplum exhibet admirandarum virium imaginationis maternæ in fœtum utero contentum. Mater enim hujus bicorporis, primis graviditatis suæ mensibus vel potius hebdomadis, attentius contemplabatur canes coëuntes, arctius cohærentes, et capitibus erga se invicem quodammodo conversos, eosque sibi crebrius præfigurabat.

II. In partu, primum prodiit umbilicotenus Helenæ corpus; post tres demum horas editi sunt ejus pedes, cum adnexo corpore altero Judithæ. Helenæ corporis statura erat altior et rectior, Judithæ brevior et obliquior; et quamvis infra lumbos, a tergo, in unum corpus concretæ fuissent, attamen vultu et corporibus, semilateraliter, erga se fuerant conversæ, ut commode sedere, lentoque gradu procedere et recedere potuerint. Unus communi ipsis erat alvi exitus, intra duas nates, seu Helenæ dextrum et Judithæ sinistrum femur, situatus. Unam quoque habebant vulvam, intra quatuor pedes reconitam, ut dum erectis starent corporibus, ne vestigium ejus conspicuum esset. Quoad duos istos excretionum meatus, observatum est, quod, una excretionem alvi moliente, altera quoque nisum egerendi senserit; in reddenda vero urina, quælibet, diverso tempore, stimulos habuerit: quamobrem altera ad urinæ missionem solicitata, altera subinde recessum negavit. Unde in juventute, utut alias semper semet tenerrime amarent et amplexarentur, sæpius altercationes inter ipsas exortæ, et alterutra aliam vel dorso injectam abripuit, vel colluctando eo, quo vellet, protraxit.

III. Anno ætatis sexto, Judithæ paralysis totius partis sinistræ; obtigit ex qua affectione, utut convaluisset, per totam vitam suam debilior, tardior, et stupidior perstitit; e contra Helena semper agilior, docilior, et formosior suit.

IV. Prout diversa erant corpora, ita functionum vitalium, animalium, et naturalium, magna in utroque corpore, tam in sano quam ægroto statu, observata est differentia. Et quamvis variolas et morbillos uno eodemque tempore habuissent, reliqui tamen morbi eis non erant communes. Cum Judith sæpius convelleretur, Helena nec alterata nec debilitata fuit. Helena erat pleuritica. Judith benigniore febre laboravit: alterâ tussi, catarrho, colicâ afflictâ, altera sana exstitit. Hinc etiam quælibet, pro suo diverso statu, diversis medicamentis tractabatur: phlebotomia autem semper in saniore et vegetiore celebrabatur.

V. Anno ætatis decimo sexto, menstrua comparuerunt, quæ deinde per totam vitam, non tamen æquali tempore, modo, et quantitate successere. Subinde alterutra majores hinc sensit molestias; Judith vero crebrius convellebatur, variisque hystericis et pectoris affectionibus obnoxia fuit.

VI. Anno ætatis vicesimo secundo, seu A. C. 1723. die 8 Febr. Judith fortiter convulsa est, postea comatosa, usque ad mortem, quæ die 23 Febr. mane contigit, perstitit. Intra hos dies Helena febricula laboravit, eique accesserunt crebriores lipothymiæ, quibus tandem ita debilitata est, ut integra quamvis mente et loquela, subito, tribusque horæ minutis prius quam Judith, in agonem inciderit: postea vero ambæ, post brevem agonem, uno ferme momento expiraverint.

VII. Corporibus post mortem dissectis, reperta sunt in quolibet corpore viscera singula: In Helena omnia sana; in Judithæ thorace vero cor nimis magnum, fortissimo pericardio velatum, et pulmonum dexter lobus putridus: Arteria aorta et vena cava ex utroque corde descendentes, antequam arteriæ et venæ iliacæ ex iisdem emergerent, inflexæ coadunabantur, et unam arteriam aortam, unamque venam cavam, e corde uno ad aliud procedentes seu reflexas, præsentarunt. In abdomine utrinque viscera omnia sana et integra. Quodlibet corpus suum habuit hepar, splenem, pancreas, renes, vesicam, uterum cum ovariis, tubis Fallopianis, et portione vaginæ, quæ utrinque concurrentes unam communem vaginam efformarunt. Partes genitalium externorum, præter commune orificium vaginæ, cuilibet erant propriæ, velut clitoris, nymphæ, orificium urethræ; alæ seu labia utrinque ad perinæum concurrentia fossulam navicularem densiorem constituerant. Ventriculus cum intestinis, in utrâque, naturaliter erant situata; intestina recta autem utrinque ad os sacrum reflexa et coalita, unum satis amplum et communem canalem constituerunt: os sacrum ad secundam divisionem concretum erat, et unum corpus efformando, in uno utrique ossi sacro communi, osse coccygis, terminabatur.

Ex prærecensitis, sicut causa diversitaris actionum et functionum patet, ita etiam ex arteriarum aortarum, et venarum cavarum, intestinorum quoque rectorum et vaginarum uteri, compagine, coadunatione et harmonia, apparet ratio conformitatis et disparitatis morborum, synthanasiæ, communis nisus egerendæ alvi, possibilis imprægnationis alterutrius, vel fors utriusque virginis, uno eodemque coitu.

Hæc omnia conquisivi et retexui, partim e relationibus fide dignis autoptarum; partim ex ephemeridibus B. Caroli Raygeri, soceri mei, qui, dum viveret, medicum cœnobii dicti ordinarium agebat; partim ex libro cœnobiali, cui B. Vir formulas medicamentorum inscripserat. Dab. Posonii die 3 Julii 1757.

Justus Joannes Torkos,
Eques Pannonius, Medic. Doct. et
Liberæ Regiæ Civitatis Posoniensis
Physicus ordinarius.

The interval between the reading of this paper before the Royal Society and the present publication, was occasioned by the long indisposition, and afterwards death, of their late President Martin Folkes, Esq; who having taken it to his house, with a view of collecting and adding to it some further particulars, it could not be found after his decease. But Dr. Torkos, the writer, being again applied to, immediately transmitted the copy of it printed above: and, in order to supply in some measure the want of what Mr. Folkes’s extensive reading and industry might have furnished the public with, in relation to so very remarkable a fact, the following accounts, printed and manuscript, are subjoined as a supplement to the preceding article.

_Extract of a Letter of_ William Burnet, _Esq; F.R.S. eldest Son of Dr._ Gilbert Burnet, _Lord Bishop of_ Salisbury, _to Dr. (afterwards Sir)_ Hans Sloane, _dated at_ Leyden, May 9. 1708. _N. S._[195]

“+SIR+,

I Send you inclosed the print of a wonderful union of two twin sisters, who are at this time to be seen at the Hague. I saw them, and observed all, that I could think tended to explain the appearance. They are Hungarians, as the lines under the print will shew you. There is there an exact enough description of their condition; only I may add, that in fig. 1. the urinal passage is between the two foremost thighs, as they are in the print. The same is true of the anus in the 2d figure, in such manner, that the situation of these parts is the same to outward appearance as naturally, with this difference, that they are between two different bodies here, whereas in the course of nature they are between the two parts of the same body. It seems probable, that their parts are distinct; but that the most remote labia of each are outwardly visible, and the two contiguous ones are within. There seems to be no cheat in the thing; and the skin, where they are joined, is perfectly smooth, without any scar. They are now about six years old. They speak French and High German. They are very full of action, and talk one more than the other. When one stoops to take up any thing, she carries the other quite from the ground; and that one of them often does, being stronger as well as more lively than the other. They have not their feeling common any where but in the place of their conjunction. This is all I can say about it. If you think it worth while, you will do me an honour in giving the print, and the substance of this account, to the Society; to which, tho’ an unworthy member, I would be proud to be capable of any service.”

This letter was read to the Royal Society on the 12th of May 1708[196]; and the print mentioned in it produced; which, being now become extremely difficult to be met with, is thought proper to be engraved again, and inserted here. _See_ TAB. XIII.

Soon after the date of Mr. Burnet’s letter the twin sisters were brought to England, and publicly shewn in London, as appears from the following MS. note in a copy of the print bound up by the writer with Fortunius Licetus _de Monstris_[197], edit. Amstelod. 1665. 4to. in the possession of Thomas Wilbraham, M.D. F.R.S. “_Londini 14 Junii 1708. has vidi gemellas (plus annis sex natas) quarum forma et vivacitas elegantior et vegetior quam pictura et descriptio._”

_Corpora Binarum sic concrevere Sororum,
Non nisi Divina dissocianda manu.
SZÖNY Patria est, vicus COMORÆ co terminus Arci,
Qvæ nunquam Lunæ paruit Imperio.
Amplexa est ulnis HELENAM Lucina priorem,
Horis deinde tribus JUDITHA fuit._

_Exitus Urinæ patet unicus, unicus alvo,
Observant numerum cætera membra suum.
Misit ad Ignotos tenuis Fortuna Parentum,
Neu pereat tantæ Fama stupenda rei.
InterIora Latent, neqVeVnt abstrVsa VIDerI:
eXIgVo totVM CorpVs In ære patet._

_J. Mynde sc._]

Another account of them by an eye-witness in London is in a manuscript volume among those of Sir Hans Sloane, Bart. in the British Museum, intituled, _A short History of human Prodigies and monstrous Births, of Dwarfs, Sleepers, Giants, strong Men, Hermaphrodites, numerous Births, and extreme old Age, &c._ The name of the writer was James Paris du Plessis. In p. 39. under the Title _Two Sisters conjoined_, he gives a drawing of them, and the following description: “These two monstrous girls were born at Szony in Hungary in the year 1701. They were born conjoined together at the small of the back. I asked the father and mother, if they could not be separated one from the other? but they answered, No; because the urinary and fœcal vessels and passages were so united, as to have but one issue for the urine, and another for the excrements, betwixt both. They were brisk, merry, and well-bred: they could read, write, and sing very prettily: they could speak three different languages, as Hungarian or High Dutch, Low Dutch, and French, and were learning English. They were very handsome, very well shaped in all parts, and beautiful faces. Helen was born three hours before her sister Judith. When one stooped, she lifted the other from the ground, and carried the other upon her back; neither could they walk side by side. They loved one another very tenderly. Their clothes were fine and neat. They had two bodies, four sleeves; and one petticoat served to the bodies, and their shifts the same. When one went forward, the other was forced to go backward.”

A later and more particular account is contained in p. 41, _& seqq._ of a book very seldom met with in this country, being printed at Vienna in 1729. intituled, _Gerardi Cornelii Drieschii Historia magnæ Legationis Cæsareæ, quam Caroli VI. auspiciis suscepit Damianus Hugo Virmondtius_, &c. The following extract, tho’ long, will not probably be thought unentertaining.

“Sunt in comitatu Commaroniensi in terris illustrissimi Zichii (pagus Hungaris Szony dicitur) à parentibus colonis, quibus sua vita constat, dum hæc scribo, anno 1701. vii calendas Novembreis procreatæ in lucem duæ filiæ gemellæ, posticâ parte, quâ spina dorsi definit, concretæ, sic ut altera alteram sequi, quo se cunque vertat, cogatur: cætera haud deformes aspectu, nisi concretio illa corporum prodigium efficeret. Binæ singulis manus, totidem pedes, et capita, necnon corpora: suus membris omnibus usus; rationis multò etiam, quod mirere, certior; ut, si sedentes solum videris, neque sciveris, hic monstri notare nihil valeas. Majori natu, quæ lucem citius aspexit tribus horis, Helenæ, minori Judithæ nomen est. Hæc ante annos circiter tres stupore apoplectico tacta linguæ modicum ex eo ac bonæ mentis officium impeditum habuit, simplicitatem quandam ingenii modo ut redoleat. Illa animo semper integro atque spiritu prædita eodem, pudicâ facie, non inconcinnis motibus, intuentium in se oculos ad misericordiam commovet, utpote quæ rationis planè compos, sororis tenerrimè amans, nec status ignara sui, duplicem miseriam tolerat, suam et istius. Ductæ sunt olim infantes per varias regiones ac provincias, Germaniam, Angliam, Galliam, Italiam, Poloniam, Bataviam, Austriam, Moraviam, Hungariam, à medico Hungarico nomine Csuszio, qui easdem certâ pecuniâ ad tempus sibi a parentibus concreditas et elocatas, bonâ eorundem veniâ, paterno à solo âbduxit; unde trium gentium linguis, Germanicâ, Gallicâ, Hungaricâ, hodiedum etiam loquuntur; alias desuetudine usuque interrupto, ætate præsertim nondum satis confirmatâ, omnino dedidicere.

Dux Augustus Saxo Cizius inter purpuratos LXXII patres à constantia religionis, timore erga Deum et caritate in proximum notissimus, archiepiscopus Strigoniensis, veritus, ne frequentes hæ perignationes puellarum adhuc infantium innocentiæ officerent, ac mores denique illarum, ut fieri non raro assolet, planè depavarent, pacto persolutoque pretio à medico redemit, et revocatas domum ad suos virginibus à divâ Ursulâ nuncupatis intra Posonium deinceps educandas commisit, necessariis ad hoc sumptibus benignè subministratis. Ingressæ non diu puerilem ætatem suerant, nonusque illis annus agi cœptus currebat, quando harum in disciplinam virginum tradebantur. Hic legere primum ac scribere, ea, quæ ad fidem necessaria sunt, mente atque animo comprehendere; operas manuum exercere varias, acu præcipuè phrygionicâ pingere, denticulatas affabre fimbrias conficere, et cætera quæ sunt ejusdem generis, edoctæ fuerunt. Vidi ego ex illarum operibus aliqua, quæ magistras hâc in arte fecisse non pudeat. Receptæ autem sunt sacrum hoc in collegium anno secul ix. die XII. kalendas Aprilis, ibi XI mansionis, vitæ XIX jam planè complerunt. Istuc divarum contubernium, quod adhuc constanter incolunt, nunquam postea deseruere. Addita illis e prudentioribus virago, quæ indefinentur adsit, quo velint, ducat, actonibus invigilet, de quibus respondere, ad aliosque referre, si necessum fuerit, aliquando possit. Ex hâc scire quæ cupiebam, remotis arbitris, nullo negotio percepi. Crediderat namque, quod res quoque erat, non curiositatis gratiâ, sed officii, ac boni publici causâ ista à me rogari: quare alios omnes secedere jussi, solus cum eadem remanens, ut quæ, junioribus præsertim aliquot præsentibus, accuratius explicare verecundia illam antea prohibuerat, majori mecum libertate communicaret. Partes, quas vel nominare pudor honestasque vetuit, per quas potus ciborumque fæces et reliqua corporis excrementa (sit verbo venia) ejicimus, non illis his, quibus nobis, constitutæ locis. Illis quidem, ubi nos eas habemus, occlusa sunt omnia; at infernè, quâ parte concretio illa corporum incipit, easdem obtinent utrique communes. Neque tamen cum necessitas alterutram premit ad exonerandum, exempli gratiâ, ventrem, altera se quoque sentit tam inutili pondere gravatam, at satisfaciendum necessario naturæ sit: sed jam huic, jam isti istud imbecillitatis humanæ incommodum perferendum est, sitque etiam, ut cum alvum purgat altera, alteri meatus sit urinarius aperiendus. Muliebria, quæ statis fœminas vicibus incommodant, non uno ambabus tempore veniunt. Octidui quandoque intervallo ac longiori disjuncta sunt. Dum dormit hæc, sæpe vigilat illa, et in alterius labore altera nonnunquam quiescit. Visa una potare est, aut cibo corpus reficere, cum aliud alii agebatur. Sedent, stant, ambulant, jacent semper unà, nec sine incommodo. Non permittit conglutinatio ista corporum, hæ uti actiones separentur. Si colloquuntur, obtortis faciem collis obvertunt. Suavia dant sibi, cum amant, et pugnis impetunt, cum furunt. Donec suæ utrique vires adhuc constabant, si sorte exortæ inter illas aliquando discordiæ essent, hæc, quæ se læsam magis credebat aut fortem, sublatam in humeros aliam alio asportabat. Veruntamen ingenio miti magis ac placido sunt quam incenso aut iracundo, et in communibus malis communem fidem, commune robur adhibent, immissam sibi à Deo miseriam fortitèr sustinentes. Ante triennium in gravi secundò genitæ morbo, de quo nonnulla superiùs facta est mentio est, prior nata sacris omnibus munita ad mortem quoque feliciter obeundam disposita ab sacerdote fuit, quia medicorum pars potior credit aliâ extinctâ aliam haud posse longùm amplius superesse. Id quod probare ex hoc etiam laborant, quod quoties male uni sit, quamvis altera non eadem continuo ægrotatione teneatur, angustias tamen animi certas, hebetationem sensuum, et commotionem quandam viscerum in seipsa experiatur. Equidem dubitandum minimè reor, quin monstrosa hæc bina corpora duplici mente ac spiritu regantur. Nam sive cor faciamus, sive cerebrum statuamus animi sedem, ex utrolibet idem nullo negotio evincitur. Adde tot actiones multiplices, cogitationes rerum diversas, sensa animi varia, quæ, ut aliud nihil sit, isthuc pariter nos docent. Unum præcipue hic admirandum venit, quod commemorare superius memoria excidit; post prodigiosum videlicet hunc difficilemque partum natos esse matri alios liberos, ex eodem patre procreatos, sanos et valentes, corpore, specie ac forma integros, qui monstri nihil admixtum habeant.”

XL. _Observations on the Origin and Use of the Lymphatic Vessels of Animals: being an Extract from the_ Gulstonian _Lectures, read in the Theatre of the College of Physicians of_ London, _in_ June 1755. _By_ Mark Akenside, _M.D. Fellow of the College of Physicians, and of the Royal Society_.

[Read Nov. 30, 1757.]

IT is proved, by a multitude of experiments, that the lymphatics communicate with the blood-vessels. They may be distended by blowing air, or by injecting water or mercury, into an artery: and the lymph, which they carry, is frequently, in a morbid state, found tinged with a mixture of the red globules or crassamentum of the blood. Upon this foundation two different theories have been raised, concerning the connection of the lymphatics with the arteries.

Of these, we shall first consider that of the late famous professor Boerhaave. He observed, that every artery of the body is greater, in its diameter, than any of its branches: and this observation being found true, as far as our eye and the microscope can inform us, he inferred, by analogy, that it held good even thro’ the most minute subdivisions of the arterial system. But, says he, proportionable to the diameter of the canal is the size of the particles moving thro’ it: therefore, if an ultimate capillary artery, admitting only one red globule at once to pass thro’ it, send off lateral branches, these branches will be capable of receiving such particles only as are smaller than a red globule. But the particles next in magnitude below the red globules are the yellow serous ones; and the lateral vessel, thus receiving them, is a serous artery, and the trunk of a second order of vessels. In like manner, this trunk, being continued on thro’ many lessening branches, will at last grow so minute, as to admit only one serous globule: its lateral branches, therefore, will receive only such particles as are smaller than the serous ones: but these are the particles of the lymph; and this lateral branch is a lymphatic artery, and the trunk of a third order of vessels. Thus, in the red arteries are contained all the circulated fluids of the body; in the serous arteries, all except the red blood; in the lymphatics, all except the red blood and serum: and this subordination is, according to the same laws, continued down thro’ fluids more subtile than the lymph, to the smallest vessel, which is propagated from the aorta. Such was Boerhaave’s doctrine concerning the vascular system of animal bodies; like many of his other notions, ingenious, plausible, and recommending itself, at first sight, by an appearance of geometrical and mechanical accuracy: but founded upon insufficient data, and by no means to be reconciled to appearances.

For, in the first place, should we admit his hypothesis, it is certain, that the conical or converging form of the aorta, and the change of direction in its branches, must, in the distant blood-vessels, occasion a great resistance to the moving blood, and a great diminution of its velocity. Suppose that this resistance be, in any capillary red artery, to the resistance in the trunk of the aorta, as any larger assignable number is to unit: the resistance, then, in a capillary serous artery will, to that in the aorta, be as the square of that number is to unit; in the capillary lymphatic, as the cube; and so in progression: that is, the velocity of the fluids, in the remoter series of vessels, will be, physically, nothing. But we know, on the contrary, that some very remote series of vessels have their contents moved with a very considerable velocity; particularly the vessels of the insensible perspiration: and in anatomical injections, the liquor thrown into an artery scarce returns more easily or speedily by the corresponding vein, than by the most subtile excretory ducts. Moreover, there are an infinite number of observations of morbid cases, in which the red blood itself has been evacuated thro’ some of the most remote series of vessels, merely from an occasional temporary obstruction in one part, or a præternatural laxity in another; and without any lasting detriment to the structure and subordination of the vessels; which yet, upon this hypothesis, must have been utterly destroyed before such an irregularity could have happened.

The other theory concerning the origin of the lymphatics has been maintained by some very eminent physiologists later than Boerhaave; and supposes, that these vessels receive their lymph from the blood-vessels, or from the excretories of the larger glands, by the intermediation of only one small vessel, which these authors term a lymphatic artery, invisible in its natural state, nor yet rendered subject to the senses by experiments. But to this it may be answered, that the lymphatics are traced into many parts of the body, and lost there; and therefore most probably have their origin there, where no large gland nor blood-vessel is to be found in their neighbourhood: that it contradicts the whole analogy of nature, to suppose the motion of an animal fluid more discernible in the veins than in the arteries: and, finally, that it seems rather an instance of want of thought, and of being imposed upon by words, to call the lymphatic vessels veins, because they are furnished with valves; and then, because they are called veins, to take for granted, that of course they must be the continuation of arteries.

In attempting to investigate matters too subtile for the cognizance of our senses, the only method, in which we can reasonably proceed, is by inferring from what we know in subjects of the same nature: and our conclusion thus inferred, concerning the subject sought, will be firmer and more unquestionable, in proportion as it resembles the subject known. But if the subjects be really of the same kind; if no difference can be shewn between them, in any respect material to the inquiry, in which we are engaged; in this case our inference from analogy becomes the very next thing to a physical certainty: and this I apprehend to be true in relation to the problem before us, concerning the origin of the lymphatic vessels. Tho’ in general we cannot, by experiments, arrive at the extremities of those tubes, nor satisfy ourselves, by inspection, in what manner they receive their fluid; yet in a very considerable number of them we can do both. There is a certain part of the human body very abundantly provided with lymphatics; in which part we can actually force injections thro’ those vessels into a cavity, where their extremities open: and from this cavity, on the other hand, we can at pleasure introduce a coloured liquor into their extremities, and trace it from smaller into wider canals; from capillary tubes, without valves, into large lymphatic trunks copiously furnished with them. We know likewise, that into this cavity are continually exhaling an infinite number of watery and mucous vessels, both arterial tubes and excretory ducts: that these keep it moist with a perpetual vapour, which the extremities of those lymphatics are, in the mean time, perpetually imbibing. Does it not seem strange, while these particulars are known and acknowledged by all the world, that the great authors of anatomy and physiology should never have reasoned from them; but should run into complex and obscure suppositions, in order to explain a process, which they may at any time examine with their own eyes? But perhaps this inadvertency may be accounted for, if we recollect, that at the time when these vessels, and the structure of this part, were discovered, the lymph, and every thing belonging to it, was utterly unknown; and that the vessels in question were first seen and considered as performing another and more remarkable office: which circumstance, it should seem, has prevented succeeding authors from being duly attentive to them in the capacity of lymphatics. However this be, it is certain, that the lymphatics of the mesentery, commonly called the lacteals, differ from those of the other parts in no one particular, save that occasionally they carry chyle instead of lymph; or rather carry lymph mixed, at stated times (that is, for two or three hours after the creature has taken food) with an emulsion of vegetable and animal substances, and coloured white by that mixture. At other times, (that is, during sixteen of eighteen hours out of the twenty-four) they contain nothing but lymph; and are, in every respect, mere lymphatic vessels, not to be distinguished from those in any other part of the body. Their structure is the same; the membrane of which they are formed, their valves, the lymph which they contain, the glands thro’ which they pass, their direction from smaller tubes to larger, and from these to the blood, differ in nothing from what we observe of the other lymphatics. Their lymph, in the mean time, is without doubt or controversy supplied from the cavity of the intestines; being the watery moisture continually exhaled there for the purposes of digestion, and for the preservation of the alimentary canal, and as continually taken up by the roots or extremities of these vessels, in order to be carried back to the blood, after it has performed its office in the bowels. Let it also be remembered, that these vessels, in other places of the body, are generally, when we trace them, lost in muscular, tendinous, or membranous parts: and then, I should presume, it may fairly, and with a good degree of evidence, be concluded, that the lymphatics of the body, in general, have their origin among the little cavities of the cellular substance of the muscles, among the mucous folliculi of the tendons, or the membranous receptacles and ducts of the larger glands: that their extremities or roots do, from these cavities, imbibe the moisture exhaled there from the ultimate arterial tubes, just as the lacteals (the lymphatics of the mesentery) do on the concave surface of the intestines: and that the minute imbibing vessels, by gradually opening one into another, form at length a lymphatic trunk, furnished with valves to prevent the return of its fluid, and tending uniformly, from the extremities and from the viscera, to reconvey to the blood that lymph, or that fine steam, with which they are kept in perpetual moisture; a circumstance indispensibly necessary to life and motion: while, at the same time, the continual re-absorption of that moisture by the lymphatics is no less necessary, in order to preserve the blood properly fluid, and to prevent the putrefaction, which would inevitably follow, if this animal vapour were suffered to stagnate in the cavities where it is discharged.

XLI. _A Letter to the Right Honourable the Earl of_ Macclesfield, _President, the_ Council, _and_ Fellows, _of the_ Royal Society, _concerning the Variation of the Magnetic Needle; with a Sett of Tables annexed, which exhibit the Result of upwards of Fifty Thousand Observations, in Six periodic Reviews, from the year 1700 to the year 1756, both inclusive; and are adapted to every Five Degrees of Latitude and Longitude in the more frequented Oceans. By_ William Mountaine _and_ James Dodson, _Fellows of the Royal Society_.

[Read Nov. 10, 1757.]

Dated London, Nov. 9th. 1757.

SIRS,

ON the 20th of March 1755, we presented an address to this illustrious Body, intituled, “An Attempt to point out, in a concise manner, the Advantages which would accrue from a periodic Review of the Variation of the Magnetic Needle, throughout the known World; requesting contributions thereto, by communicating such observations concerning it, as had then been lately made, or could be procured from correspondents in foreign parts.”

This address was read at the same time, and afterwards honoured with a place in the Transactions, vol. xlviii. part ii. for 1754: which favour we now acknowledge in the most grateful manner; and, pursuant to our engagements, beg leave to lay before you some account of the communications received, with a specimen of the uses and applications which we have been enabled to make of those, and other assistances with which we have been indulged.

On application to the Honourable the Commissioners of the Navy, we were obliged with an order of free access to all their masters log-books and journals.

The Directors of the Honourable East India Company granted the like privilege.

The Honourable Committee of the Hudson’s Bay Company obliged us with sundry observations, made, and tabulated, by their own Captains.

James Bradley, D. D. Regius Professor of Astronomy, and F.R.S. favoured us with several observations made at the Royal Observatory at Greenwich.

John Hyde, Esq; F.R.S. communicated a sett of useful observations, extracted from two journals kept on board the Triton and Britannia East Indiamen.

A correct journal kept on board the Delawar East Indiaman was handed to us by a gentleman unknown.

Capt. George Snow furnished a considerable number of observations, made with care and accuracy by himself, in several successive voyages to, and from Barbadoes and Virginia; together with several remarks upon the subject: _One_, which we apprehend to be material, we beg leave to insert, as it meets with some confirmation by the tables annexed; _viz._ “At Barbadoes the variation seems at a stand very near; for in the road, 1752, I observed 5 degrees east; and by Mr. Halley’s draught, in the year 1701, 5½ degrees: in 1747, at Port Royal keys, Jamaica, I observed the variation 7° 20’ E.; and on the coast of Carthagena the same week, off the high land of Sancta Martha, 7° 45’ E. nearly south of Port Royal: Therefore these curves are not much altered; and the curve at Jamaica is nearly at a stand, as tho’ tied; and the south part of them, with the rest, dropping to the westward.”

Mr. Mungo Murray, author of a treatise on ship-building, presented us with several observations taken on board the Prince Edward and Chesterfield East Indiamen, and his Majesty’s ship the Neptune.

For all these favours we return our sincere thanks.

No observations made upon land have been received, except Dr. Bradley’s aforesaid; which has frustrated our intentions of continuing the curves from sea to sea.

By collecting, comparing, and adjusting, all these materials, we have been enabled to construct variation-curves upon Dr. Halley’s mercator-chart, adapted to the year 1756; which will soon be in readiness to present to this Royal Society.

As a work of this kind requires much time, and a multitude of observations, both by sea and land, to render it more perfect and general; we hope the ingenious in all nations will lend their assistance: By this means every periodic review will be productive of improvement.

From the first instant that we made this affair the object of our more particular consideration, we have attended to the mode of increase and decrease in the variation: and as a considerable number of observations, made at periodic times, and duly registered, seem to be the most essential toward determining the laws of its mutation, or proving its irregularity, we have therefore formed a sett of tables, from actual observations collected for the years 1710, 1720, 1730, and 1744, the date of our last chart; which, together with Dr. Halley’s for the year 1700, and the present chart now publishing, compleat six reviews: These are tabulated, and shew the quantity of the variation, at those several periods, to every 5 degrees of latitude and longitude in the more frequented oceans; which we hope will prove acceptable, as nothing of the like kind has yet appeared, or can easily be obtained.

Our materials have been so deficient, that even in the limits to which our tables are confined, we have been obliged to leave blanks in some of the above periods, for want of that concurrent testimony, on which the numbers inserted are founded: but, considering the difficulties unavoidably attending a work of this sort, and the little assistance which we have met with from private hands, we hope that this Royal Society will not only excuse those vacancies, but also those in the great tracts of sea, as well as land, concerning which we are very unwillingly obliged to be intirely silent.

Agreeable to our former address, we lay only what appear to be facts before you, without attempting to introduce any hypothesis for the solution of these phænomena; some of which (being very extraordinary) we recommend peculiarly to the notice of those gentlemen, who may endeavour the investigation of their causes.

Under the equator, in longitude 40° E. from London, the highest variation during the whole 56 years appears to be 17°¼ W. and the least 16°½ W.: and in latitude 15° N. longitude 60° W. from London, the variation has been constantly 5° E. but in other places the case has been widely different; for in the latitude 10° S. longitude 60° E. from London, the variation has decreased from 17° W. to 7°¼ W., and in latitude 10° S. longitude 5° W. from London, it has increased from 2°¼ W. to 12°¾ W.; and in latitude 15° N. longitude 20° W. it has increased from 1° W. to 9° W.

But there is still a more extraordinary appearance in the Indian seas: for instance, under the equator,

Longitude from| Variation in
_London_ | 1700. | 1756.
--------------+----------+---------
Degrees. | Degrees. | Degrees.
40 E | 16¾ W | 16¾ W
45 E | 17¾ W | 14½ W
50 E | 17½ W | 11¾ W
55 E | 16½ W | 8¾ W
60 E | 15¼ W | 6 W
65 E | 13½ W | 4½ W
70 E | 11½ W | 2¾ W
75 E | 9¾ W | 1 W
80 E | 7¾ W | 0¼ E
85 E | 5½ W | 1¼ E
90 E | 4¼ W | 1 E
95 E | 3¼ W | 0½ W
100 E | 2½ W | 1 W
--------------+----------+---------

Where the west variation in the longitude 40° E. is the same in both the above years; and in 1700 the west variation seemed to be regularly decreasing from longitude 50° E. to the longitude 100° E.; but in 1756 we find the west variation decreasing so fast, that we have east variation in the longitude 80°, 85°, and 90° E; and yet, in the longitude 95° and 100° E. we have west variation again.

Such are the irregularities, that experience hath shewn us, in the variation of the magnetic needle; which appear so considerable, that we cannot think it wholly under the direction of one general and uniform law; but rather conclude, with the learned and judicious Dr. Gowen Knight, Fellow of this Society, in the 87th prop. of his treatise upon attraction and repulsion, That it is influenced by various and different magnetic attractions, in all probability occasioned by the heterogeneous compositions in the great magnet, the _Earth_.

Notwithstanding all which, should the sagacity of some eminent philosopher be able to exhibit rules, whereby the quantity of the variation may be computed for future times, yet then such a review, as we have now made, will be necessary at a proper interval, to prove the truth of them: and should no such rules appear, then will a continued succession of such reviews be necessary so long as commerce and navigation subsist among us.

What we have now done is intirely for the public service, the sale of the former chart never having made good its expence; and we propose to continue our endeavours for another review, at the proper time, if we shall then be alive, and capable of the task: but as the contrary may probably happen, we beg leave to conclude with recommending such a continuation, in the strongest manner, to such of the members of this Royal Society, or others, who may, at the proper intervals, have leisure and ability for such a performance.

We are, with the greatest deference,

Your Lordship’s,
And the Royal Society’s,
Most faithful and
most obedient Servants,
William Mountaine.
James Dodson.

_A_ TABLE, _exhibiting the different Variations of the_ MAGNETIC-NEEDLE _in the more frequented Oceans, from the Year 1700 to the Year 1756_.