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O N D O N.

V O L. LXXV. For the Year 1785,





^ *DAII8ia.B




[ iii ]


TH E Committee appointed by the Royal Society to dire^l the pub-
lication of the Fhilofophical 'TraJifatlions, take this opportunity to
acquaint the Public, that it fully appears, as well from the council-books
and journals of the Society, as from repeated declarations which have
been made in feveral former Tranfdclions, that the printing of them was
always, from time to time, the fingle aft of the refpeftive Secretaries, till
the Forty-feveuth Volume : the Society, as a Body, never intereflingthem-
ielves any further in their publication, than by occafionally recommending
the revival of them to fome of their Secretaries, when, from the particular
circumflances of their affairs, the Tranfadions had happened for any
length of time to be intermitted. And this feems principally to have
been done with a view to fatisfy the Public, that their ufual meetings
were then continued foj- the improvement of knowledge, and benefit of:
mankind, the great ends of their firfl: inflitution by the Royal Charters,
and which they have ever fince fteadily purfued.

But the Society being of late years greatly inlarged, and their com-
munications more numerous, it was thought advifable, that a Committee
of their members fliould be appointed to reconfider the papers read be-
fore them, and feleft out of them fuch, as they fhould judge moft pro-
per for publication in the future 'Tranfadions ; which was accordingly
done upon the 26th of March 1752. And the grounds of their choice
are, and will continue to be, the importance and fingularity of the fub-
3 efts, or the advantageous manner of treating them; without pretending
to anfwer for the certainty of the fafts, or propriety of the reafonings,
contained in the fevtral papers f© publiflied, which muft dill reii on the
credit or judgment <:f their refpeftive authors*

A 2 It

E iv 1

It ]s likewife neceiTary on this occafion to remark, that it is an efla - -
bliflied rule of the Society, to which they will always adhere, never to
give their opinion, as a Body, upon any rubje6t, either of Nature or Art,.
that comes before them. And therefore the thanks, which are fre-
quently propofed f\-om the chair, to be given to the authors of fuch pa-
pers as are read at their accuftomed meetings, or to the perfons through:
whofe hands they receive them, are to be confidered in no other light
than as a matter of civility, in return for the refpefi iliewn to the Society
by thofe communications. The like alfo is to be faid with regard to
the fever al projects, inventions, and curiofities of various kinds, which
are often exhibited to the Society ; the authors whereof, or thofe wh^
exhibit thera, frequently take the liberty to report, and even to certify
in the public news-papers, that they have met with the highefl applanfe
and approbation. And therefore it is hoped, that no regard will here -
after be paid to fuch reports, and public notices ; which in fome inftances?
have beert too lightly credited, to the diflionour of the Society,


■'"■■"* ■■• ■ '■" ' -.—-,.- . ,. ... - ■ »- — ^ ^



O L. LXXV. Part I.

I* ^'^ Account of an arttficial Spring of Water. By Eraf-

mus Darwin, M. T>. F. R, S, page i

-IL An Account of an Englifli Bird of the Genus Motacilla,

fuppofed to be hitherto unnoticed by Britiih Ornlthologljis ;

obferved by the Rev. John Lightfoot, M. A. F. R. S. In a

Letter to Sir Jofeph Banks, Bart, P. R. S. p. 8

III, An Account of Morne Garou, a Mountain In the JJland of
St. Vincent, with a Defcrlptlon of the Volcano on Its Summit.
In a Letter from Mr. James Anderfon, Surgeon^ to Mr.
Forfyth, His Majefiys Gardener at Kenlington ; commtml"
cated by the Right Honourable Sir George Yonge, Bart.
F.R.S. p. i6

IV. A Supplement to the Third Fart of the Paper on the Sum-
mation of Infinite Series, In the Philofophical Tranfa6llons



for the Tear 1782. By the Rev, S. Vlnce, M. A;
commu?ilcated by Nevil Mail'Celyne, D, D, F, R, S, a?id
Aflronomer Royal, P* 32

V. Defer iption of a Plant yielding Afa fcetida. In a Letter

from John Hope, M. D. F. R. S. to Sir Jofeph Banks,

Bart, P. R S, p. 36

V!. Gifahgue of Double Stars, By William Herfchel, Efq,
F. R. S. p. 40

VII. Obfervations of a new Variable Star, In a Letter from
Edward Pigott, Efq, to Sir H. C. Englefield, Bart.F. R, S,
a?]d A. S. P« 127

Vill. Afironomical Obfervations^ In two Letters from M.
Francis de Zach, Profeffor of Mathematics^ and Member of
the Royal Academies of Sciences at Marfeilles, Dijon, and
Lyons, to Mr. Tiberius Cavallo, F. R. S. p. 137

IX. Obfervations of a new Variable Star. By John Goodrlcke,
Efq. ; communicated by Sir H. C. Englefield, Bart. F. R. S,
and A. S. p. I ^"^

X. On the Motion of Bodies affeSicd by FriSlion, By the Rev,
Samuel Vince, A.M. communicated by Ainhony Shepherd,
D. D. F. R. S, Plumian Profejfor of Afrommy and experi'
77icntal Philofophy at Q^rcihn^gQ. P* ^^5

XL Obfervations and Experiments on the Light of Bodies in a
State of Combuftion. By the Rev. Mr. Morgan ; communicated
by the Rev. Richard Price, LL.D. F.R.S. p. 190

XII. On theConjlrudiion of the Heavens, P^'WIUIam Herfchel,
Efq. F.R.S. p. 213

XIII. Remarks on fpecifc Gravities taken at different Degrees of
Heat^ and an eafy Method of reducing them to a common Stan-
J/ird. By Richard Kirwan, Efq. F.R.S. p. 267




XIV. Ele5frical Experiments made in order to ajcertain the non-
condubling Power of a perjedl Vacuum^ &c. By Mr. Wil-
liam Morgan ; communicated by the Rev. Richard Price,
LL.D. F.R,S, p. 272

XV. Experiments and Ohfervations relating to Air and Water ^
By the Rev. Jofeph Prieftley, LL.D. F.R,S. p. 279,

THE Prefident and Council of the Royal Society adjudged,
for the Year 1784, the Medal on Sir Godfrey Copley's

Donation, to Edward Waring, M. D. Lucafian Profeflbr
pf the Mathematics at Cambridge, for his Mathematical
Communications to the Society*



I. An Account of an artificial Spring of IFatev, By Erafmus

Darwin, M, D, F. R, S,

Read November 4, 1784.
To the Prefident and Fellows of the Royal Society.

GENTLEMEN, Derby, July 16, 1 784.

CONFIDENT that every atom which may contribute to
increale the treafury of iifeful knowledge, whicli you are
fo fuccefsfully endeavouring to accumulate, will be agreeable
and intei^fting to the Society, I fend you an account of an
artificial fpring of water, which. I produced laft fummer near
the fide of the river Darwent in Derby.

VoL.LXXV. B Near

2 . Z)r. DAU'WiirSi'/^ccoufn of

Near thy houfe was an old well, about one hundred yards
from the river, and about four yards deep, which had been
many years difufed on account of the badnefs of the water,
w^hich I found to contain much vitriolic acid, with, at the
fame time, a flight fulphureous fmell and tafte ; but did not
Carefully analyfe it. The m.outh of this well was about four
feet above the furface of the river ; an<l the ground, through
which it was funk, confifted of a black, loofe, moiit earth,
which appeared to have been very lately a morafs, and is now
Covered with houfes built upon piles. At the bottom was
found a bed of red marl, and the fpring, which was fo ftrong
as to give up many hogfheads in a day, oozed from between
the morafs and the marl : it lay about eight feet beneath the
iurf ice of the river, and the water rofe within two feet of the
top of the well.

Having obferved that a very copious fpring, called Saint
Alkmund's well, rofe out of the ground about half a mile
higher on the fime fide of the Darwent, the level of which I
knew by the height of the intervening wier to be about four or
five feet above the ground about my w^ell ; and having obferved,
that the higher lands, at the diftance of a mile or two behind
thefe wells, conlified of red marl like that in the well ; I
concluded, that, if I fhould bore through this ftratum of marl,
i might probably gain a water fimilar to that of St. Alkmund's
well, and hoped that at the fame time it might rife above the
furface of my old well to the level of St. Alkmund's.

With this intent a pump was firft put down for the
purpofe of more eafily keeping dry the bottom of the old well,
and a hole about two and an half inches diameter was then
bored about thirteen yards below the bottom of the well,
till fome l^-^nd w^as brought by the auger. A wooden pipe,
^ which

an artificial Spri^ig of lValct\ j

wliicli was previoufly cut iu a conical form at one end, an 4
armed with an iron ring at the other, was driven into the top of
this hole, and flood np about two yards from the bottom of
the well, and being furrounded with well-rammed clny, the
new water afcended iu a fmall ftream through the wooden

.Our next operation was to build a wail of clay againil: the
moraiiy fides of t]ie well, with a wall of well-bricks inter-
nally, up to the top of it. This completely flopped out every
drop of the old water; and, on taking out the plug which
had been put in the wooden pipe, the new water in two or
three days role up to the top, and flowed over the edges of the

Afterwards, to gratify my curiofity in feeing how high the
new fpring would rife, and for the agreeable purpofe of pro-
curing the water at all times quite cold and frefh, I directed
a pipe of lead, about eight yards long, and three-quarters of
an inch diameter, to be introduced through the wooden pipe
defcribed above, into the flratum of marl at the bottom of the
well, fo as to fland about three feet above the lurface of the
ground. Near the bottom of this leaden pipe was fewed,. be-
tween two leaden rins-S or {l^iieties,? an inverted cone of iliff
Ipatherjriiatp.jyhich fome wool was, fluffed to ftretch it out, fo
that, after having pafled through ttje \yopden pipe, it might
'^completely fill .up the perforatipn of the clay. Another, leaden
ring or flanch was foldered round the leaden pipe, about two
yards below th;e fqrface of the ground, wdiich, with fome dou-
bles of flannel placed under it, was nailed on the top of the
-wooden pipe, by w^hich means the water was perfedlly pre-
cluded froni rifing between the wooden and the leaden pipes.

B 2 Tliis

4 Dr, Darwin's Account of

This being accompllfhed, the bottom of the well remained
quite dry, and the new water quickly role about a foot above
the top of the wdll in the leaden pipe ; and, on bending the
mouth of this pipe to the level of the furface of the ground,
about two hogfheads of water flowed from it in twenty- four
hours, which liad fimilar properties with the water of St. Alk-
mund's well, as on comparifon both thele waters curdled a
folution' of foap in fpirit of wine, and abounded with calca-
reous earth, which was copioufly precipitated by a folution of
fixed alkali; but the new water was found to poffefsa greater
abundance of It, together with numerous imall bubbles of
rlVial acid or calcareous gas.

The new water lias now flowed about twelve months, and, as
far as 1 can judge, is already increaied to almoft double the quan-
tity in a given time ; and from the rude experiments I made, I
think it is now lefs replete with calcareous earth, approaching
gradually to an exact correfpondence with St. Alkmund's well,
as it probably has its origin between the lame ftrata of earth.

As many mountains bear inconteftible marks of their having
been forcibly railed up by fome power beneath them ; and
other mountains, and even iflands, have been lifted up by fub-
terraneous fires in our own times, we may fafely reafon on the
lame fuppoiition in refpedt to all other great elevations of
ground. Proofs of thefe circumftances are to be feen on both
fides of this part of the country ; whoever will infpe£l, with
the eye of a philofopher, the lime-mountain at Breedon, on
the edge of Leicefierfhire, will not heiitate a moment in pro-
nouncing, that it has been forcibly elevated by fome power
beneath it ; for it is of a conical form, with the apex cut off,


{in cirUficial Spring of Water. o

and the ftrata, which compofe the central parts of it, and
which are found nearly horizontal in the plain, are raifed
almoft perpendicularly, and placed upon their edges, while
thofe on each fide decline like the furface of the hill ; fo that
this mountain may well be reprefented by a bur made by forc-
ing a bodkin through feveral parallel flieets of paper. At Rou-
ter, or Eagle-ftone, in the Peak, feveral large mafies of grit-
ilone are ieen on the fides and bottom of the mountain, which
by their form evince from what parts of the fummit they were
broken off at the time it was elevated ; and the numerous loofe
ftones fcattered about the plains in its vicinity, and half buried
in the earth, muft have been thrown out by explofions, and
prove the volcanic origin of the mountain. Add to this the
vafb beds of toad-flone or lava in many parts of this county,
fo accurately defcribed, and fo well explained, by Mr. White-
hurst, in his Theory of the Formation of the Earth.

Now as all great elevations of ground have been thus railed
,by fubterraneoiis fires, and in a long courle of time their fum-
mits have been worn away, it happens, that fome of the more
interior ftrata of the earth are expofed naked on tiie tops of
mountains; and that, in general, thole flrata, which lie up-
permoft, or neareft to the fummit of the mountain, are the
loweft in the contiguous plains. This will be readily con-
ceived if the bur, made by thrufling a bodkin through feveral
parallel fheets of paper, had a part of its apex cut off by a pen-
knife, and is fo well explained by Mr. Michell, in an inge-
nious paper on thePhasnomena of Earthquakes, publifhcd a few
years ago in the Philofophical Tran factions.

And as the^ more elevated parts of a country are fo much
colder than the vallies, owing, perhaps, to a concurrence ot


S T)r, Dar wind's Account of

two or three caufes, but particularly to the lefs condenfed fmte
:of the air upon hills, which thence becomes a better condu£lor
■of hiCat, as well as of eleclricity, and permits it to efcape the
fafler ; it is from the water condenfed on thefe cold furfaces of
mountains, tliat our common cold Iprings have their origin ;
and which, (liding between two of the ftrata above defcrlbed,
•defccnd till they find or make themfelves an outlet, and will la
confequence rife to a level with the part of the mountain where
•they originated. And hence, if by piercing the earth you gain
a fpring between the fecond and third, or third and fourth
flratum, it mufl: generally happen, that the water from the
loweft ilratum will rile the higheft, if confined in pipes, be-
'Caufe it comes originally from a higher part of the country in
its vicinity.

The increafmg quantity of this new fpring, and its increafing
purity, t fuppofe to be owing to its continually diffolving a
part of the earth it palles through, and hence making itfelf a
wider channel, and that through materials of lefs folubility.
Hence it is probable, that the older and flronger fprings are
generally the purer ; and that all fprings were originally loaded
with the foluble impurities of the flrata, through which they

Since the above-related experiment was made, I have read
with pleafure the Ingenious account of the King's wells at
Sheernefs, In the laft volume of the Tranfadions, by Sir
Thomas Hyde Page, in which the water rofe three hundred
feet above its fource in the well ; and have alfo been informed,
that in the town of Richmond, in Surrey, and at Infhip near
Preflon in Lanca(hire, it is ufual to bore for water through
a lower ftratum of earth to a certain depth ; and that when it


an artificial Spring of Water, j

is found at both thofe places, it rifes lb liigli as to overflow the
furface of the well : all thefe fads contribute to eftablifli the
theory above-mentioned. And there is reafon to conclude,
that if fimilar experiments were made, artificial fprings,
rifing above ground, might ia many places be thus produced
at fmall expence, both for the common purpofes of life,
and for the great improvement of lands by occafionally water*
ing them.

E 8 ]

J I. .In Accoimt of an Engllfli Bird of the Genus Motacllk,
fuppofed to be hitherto unnoticed by Britifli Ornithologijis ;
obferved by the Rev, John Llghtfoot, M. A, F. R, S. In a
J ,etter io Sir Joieph Banks, Bart. P. R. S.

Read November 1 8, 1784.

SIR, Uxbridge, Nov. 20, 1783.

AS every dilcovery in natural hiftory is efteemed worthy the
notice of that Society which was inftitiited on purpofe to
improve natural knowledge, I have taken the liberty to fend
you a defcription and drawing of a bird which haunts the
reeds of the river Coin, in the neighbourhood of Uxbridge,
and wliich feems to have hitherto efcaped the notice of writers
on Britifh Ornithology; and therefore fome account and de-
fcription of it will not, I trud:, be unacceptable to the Society
over which you lb laudably prefide.

The neft and eggs of the bird I am about to defcribe firjd:
attrafted my attention, and led to the difcovery of the bird
itfelf. They were repeatedly brought by a fifherman on the
Uxbridge river, in the parifh of Denham, to her grace the
Duchefs Dowager of Portland, who firft communicated them
to me. They were fuppofed by the fiflierman to belong to the
Sedge-bird of Pennant, or MotacilU Salicaria of Li N n^eu s ; but
being well acquainted with the nefl and eggs of this, I was very
fure he was miftaken, though he actually produced this bird as
the true proprietor of the fubje6ls in queftion. The flru6lure
and pofition of the nefb having a fingular appearance, and both


Mr» Lightfoot''s Account of a new Englifli Bird, ^

that and the eggs belonghig to a bird unknown to me, I became
defirous of finding out the fccret architect, and to that end made
life of fuch means as I thought mod likely to promote the?

Ill a fhort time my expedations were gratified ; for on the
26th day of July, 1783, intelligence was brought me, that
fuch a neil: as I wanted was found. I had given pre-
vious direction, that it fliould not be diiturbed before I had
leen it. Upon examination, I inflantly perceived it to be of
the fame kind and flru£lure with that under enquiry, contain-
ing two eggs, and two young ones juft excluded from the fhell.
One of the old birds was fitting at this time upon the neft,
which a perfon in company attempting to feize, it flew at him
with fo much refentment and acrimony, as to draw blood from
the hand that dared to moleft its inflinclive operations. Both
the parent birds continued hovering about their neft with much
watchful care and anxiety, while I made feveral attempts to
take them alive ; but, finding all endeavours in vain, left I
(hould lofethe opportunity of examining them with accuracy,
I at length, with relu£lance, caufed them to be (liot. From
thefe fpecimens the following defcriptions were made, which,
with an accurate drawing of one of them, together with its
neft and egg, are humbly fubmitted to your notice.

From the generic chara(9:ers delivered by LinnjEus, our bird
m^ft evidently be reduced to the family of his Motacilh, for it
has a weak, flender, fubulate bill, almofi: ftraight ; the man-
dibles nearly equal ; the noftrils oval and naked, or not covered
with briftles ; the tongue lacerated at the extremity ; the legs
{lender; the toes divided to the origin, except that the exterior
one is joined, at the under part of the lafl joint, to the middle
toe ; the claws of nearly equal length.

Vol. LXXV. " C The

ID -W'' Light foot's Account of ■

The male and female have the fame coloured plumage, fo
that one delciiptlon will ferve for both. They differ a little in
fize, but their external appearance is the fame. They are both
larger than the Pettycbaps defcribed by Willoughby j fmaller
than the White-throaty and nearly of the fame lize with the
JVilloW'Wren ; but to be maore particular.

The cock-bird weighed, when jufl killed, exadly (ewtn.
pennyweights and nine grains ; the hen fix pennyweights and
nine grains, or one pennyweight lefs.

The males meafured, from tip to tip of the extended wings,
feven inches and a half; the female fix and three-quarters.

From the end of the bill to the extremity of the tail, th&
cock meafured five inches and a half; the hen only five

The bill in both meafured half an inch, which is longer
in proportion than in mofl: of this genus. The tipper mandi-
ble is of a dark horn colour, (lightly incurved near the extre-
mity, with a minute indenture on either fide near the point ;
the lower is pale red or flefh- coloured, with a fhade of yellow ;
the inlide of the mouth deep orange-coloured ; the tip of the
tongue cloven and ciliated ; the noflrils oval, and deflitute of a
briftly covering ; but at the bafe of the upper mandible, on
either fide, near the angle of the mouth, arife three fhort vi-
b7'iffce pointing downwards, black at their fummits, white at
their bales ; a circumfl:ance common to many others of this
genus. The iris of the eye is olive-brown ; the pupil black.
The fhort feathers of the orbits or eye-lafhes are of a dirty
white colour. From the corner of each eye to the noflril is a
broad flroke or band of tawny-white feathers, lying ov^er each
other, and running narrowefl: towards the bill ; this affords an
excellent mark to diftinguifh the fpecies^


a ficw ^ngWih Bird. ji:

♦ The feathers of the head, neck, back, coverts of tiie wings nr.d
rump, are of an olive-brown, with a flight tinge; of green. The
quill and tail feathers are all of a darker hue, orfimply brown ;
their outward edges of a paler fhadc. The tall is two inches.
long, nightly cuneated, the middle feathers being a little longer
than the reft, the others gradually fliorter ; all of one uniforin
(kin-brown colour edged with paler brown, and a little wedge -
fhaped at their ends. - . ; .fj[

The chin is white ; the throat, breafl, belly, and parts about'
the vent, are white with a (light fhade of buff or tawny -,
but all thefe feathers (as in feveral others of this genus) when
blown afunder, or clofely examined, are found to have their
bafe or lower half black, except the fhafts, which .are'
white throughout, .:rj

, The ridge and under coverts of the exterior angle of the
wing are of a yellowifh-tawny colour, as are alfo the feathxcrs
of the thighs ; but thofe of the knees are a fhade darker, or a
pale yellowilh brown.

The legs arc a light olive ; the foles of the feet bright yel-
low, with a tinge of green, which foon fades after the bird is
dead. The inflep is covered with feven large imbricated fcalesy>
and five fmaller on the toes, as in others of the genus. The
toes {land three before, and one behind ; the claws are nearly
of equal length and curvature; but the hindmofl: is thickefl
and itrongefl.

From the foregoing remarks it is evident, that the bird men-
tioned is a fpecies of Moladlla, which, as I can find no fucli
defcribed by any fyftematic writer, I fliall venture to name,
after the Linnjean manner,

Motacilla {arundinaced) fupra olivaceo-fufca, fubtus al'bida,
lori? ^t Qrbitis fufco-albefcentibus, aagulo carpi fubtus

C ^ luteo-

12 Mr, Lightfoot's Account of

Juteo-fulvo, Cauda fubcuneata fufea, plantis luteo-

In regard to fynonyms, the only author I can find who can
be fufpeded of having noticed this bird is Sepp, who, in a late
fplendid work, in the Dutch language, Intituled, Nederl'andfche
Vogelen ffol. chart. max,) p. i o i , has defcribed and figured a bird,
under the name of Turdus arundinaceus minimus^ called . in Hol-
land Karrakietje, which in many refpe£ls agrees with our bird ;
but as the colour of the wings in that figure is made a reddifh
brown, inflead of an olive-brown, and the tawny- white Lor a
(a moft effential chara^lier to diflinguifh the fpecies) are not at
all exprefled j and the eggs are made to be of a pale-blufh colour
with dark fpots, inftead of a dirty-white with olive fpots ; I.
cannot pronounce for certain, that the bird there intended by
that writer is the fame which we have now defcribed; though,

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