_Fig._ 1, 2, 3, 4, 5, 6, 7, 8. exhibent quasdam noctilucas, et alia
animalcula in diversis corallinis reperta, ea magnitudine, qua tertia
et quarta lens microscopii à Dº. Cuff in Anglia fabrefacti illa
ostendit.
Animalculum _c_, fig. 8. mirabilissimæ erant structuræ, et plurima
habebat membra.
XXXIII. _Remarks on Dr._ Job Baster’s Observationes de Corallinis, &c.
_printed above, p. 258. In a Letter to the Right Honourable_ George
_Earl of_ Macclesfield, _President of the R. S. from Mr._ John Ellis,
_F.R.S._
[Read June 9, 1757.]
My Lord,
I HAVE read Dr. Job Baster’s letter to the Royal Society; wherein
he endeavours to prove, that corallines are not of an animal, but a
vegetable nature; and has brought many arguments to support his system;
which, to gentlemen not well acquainted with the subject, may appear
plausible.
I could have wished the Doctor had read and examined thoroughly what
has been lately written on the subject: I then should not have had
occasion to trouble your Lordship with the following remarks, which I
find necessary to support what I have already advanced on that head.
His first argument is, That because he does not find as many polypes in
the corallines adhering to ships, flood-gates, and buoys, as in deep
water on oysters, muscles, and rocks, therefore he concludes, that
corallines are not formed by polypes.
In answer to this, let us examine the pliable structure of these
bodies, and how wisely nature has defended such tender substances with
a tough thin membranaceous covering, and we shall find, that the sea is
calm enough often near the surface to give them time to grow, even in
the strongest currents: but, without doubt, they are more liable to be
destroyed in such agitated situations, than in the calm depths of the
sea.
His second argument is, That finding polypes are not equally dispersed
over the whole plant, how can they form it? and gives us an example,
_Tab._ VIII. _fig._ 5. of a coralline, that is incrusted with many
other corallines or polypes on the stem, but has none on the branches.
Here we plainly see the mistake: the Doctor looks for the tender part
of the polype on the surface of the coralline, considering it as a
plant; and indeed, if this was the case, he ought so to do; but he
never once takes notice of the internal hollow structure of the stem,
branches, and denticles of those bodies, to inform us whether he found
an animal in those parts or no. This material point he seems not to
have thought on; which is really the true point in controversy at
present among gentlemen, who have not examined these bodies recent in
sea-water.
His third argument is, That almost always one and the same coralline
plant cherishes polypes of different kinds; and refers us to Tab. VIII.
fig. 2. and 4.
In fig. 2. he gives us an elegant painting of a geniculated red
conserva for a coralline, surrounded, as is very common, by many
species of small corallines and escharas. And in fig. 4. he gives us a
drawing of one of the tubular corallines, with the head of the animal
at the top of it; the stem of this is incrusted with four different
corallines and escharas, like the conserva fig 2.; and then he asks,
which of these five polypes made the tubular coralline?
To give him some proof of the animal nature of this coralline, let him
consult Ray’s Synopsis, ed. 3. p. 34. n. 4. and there he will find one
of his species, called _adianti aurei minimi facie planta marina_,
taken notice of so long ago as the year 1713. by Dr. Lloyd, as a
zoophyte, from its stem or tube’s being full of a thick reddish liquor,
rather resembling blood than the juice of a plant; which, upon pressing
the stem, communicated with the little head at top.
His fourth argument is, That as upon one and the same coralline plant
you shall find different kind of polypes; so, in different species of
coralline, the same polypes; and, to confirm this, he quotes my Essay
on Corallines; where I have remarked, that the polypes in the denticles
of the setaceous or bristly coralline, Nº. 16. appear to be like those,
that are on the lobster’s horn coralline, Nº. 19. And to illustrate
this, he observes, that bees and wasps always build their cells
invariably the same; and that therefore these two corallines should be
the same.
But herein he takes this matter wrong: he has considered, in all his
observations, the heads of those parts of the polype, in which are
the mouths, arms, or tentacula, which appear coming out of the cups,
denticles, and at the ends of the tubes of the corallines, as so many
whole and intire animals, without every observing, that the body
of the animal is contained in the tubular part of the root, stem,
and branches; and that these differ from one another widely both in
size and shape, as he may plainly see in the two corallines he has
instanced: for the more exact drawings of which, I shall refer him,
_viz._ for the setaceous or bristly coralline, to my Plate, Nº. 38. the
natural size of which is at fig. 4. and the magnified one at fig. D:
this he will observe to have a small stem, and its branches disposed in
a pinnated form: and for the lobster’s-horn coralline, I shall refer
him to Tab. xxii. of Vol. xlviii. of the Philosophical Transactions;
where, at Nº. 3. the natural size is expressed, and at C the upper part
of this coralline is drawn in proportion to the bristly coralline from
the same magnifying glass; which shews the stem to be much larger, and
surrounded by its branches growing in whorles at equal distances, not
unlike the equisetum, or horse-tail plant; and yet the heads of this
animal nearly resemble the other, only a little larger. Further, his
comparison to bees and wasps, and their cells, is not conclusive: for
these ramified, hollow, and denticulated bodies, called corallines,
which we so frequently find dead on our shores, are properly skins of
certain marine polypes, and not nests, as those constructed by these
little winged animals are. And yet we find as great a regularity in
the same species of these corallines, as when we compare two oak trees
to one another, or two of Mr. Trembley’s branched fresh-water polypes
to one another.
He then proceeds to his fifth argument, That if corallines were formed
by polypes, neither the polypes, nor even their cells, would ever fix
on living animals, or any other bodies.
Here we may observe, that the consequence he draws doth not follow; for
corallines may be formed or produced by certain species of polypes, and
yet polypes of another species may be found adhering to other bodies,
and even to animal bodies.
By his sixth argument he endeavours to prove, That the vesicles, which
are found in regular rows on the sea-fir coralline in winter, Tab.
VIII. fig. 6. do not belong to it; and are no more than the eggs of
some sea insect deposited on it, of which there may be a great variety.
But to convince him of his mistake, let him take off one of the
vesicles, and apply a large magnifier to the place, and he will
discover a hole, by which this vesicle or ovary has had a communication
thro’ the skin with the parent polype. For a further illustration of
the manner in which these vesiculated polypes breed, let him consult
the 38th Plate of my Essay, where he will find several accurate figures
(drawn by Mr. Ehret from the life) of these vesicles, with the spawn
of the polypes coming out of them; some of which spawn we evidently
discovered to be young polypes with their arms formed; and, as they
fell from the vesicle, extending themselves in the watch-glass of
sea-water.
In examining the drawings for his plates, I have observed, that Tab.
VII. fig. 2. is evidently a red conserva, which he calls a coralline.
We have no corallines, but many conservas, of this form and bright red
colour on our coasts; and these shores, I believe, are allowed to have
similar marine productions with those of Holland.
Tab. VII. fig. 5. he calls a branch of red coralline, which he says he
kept several weeks in sea-water, and that often changed; during which
time it sprouted and grew very much. This experiment, I am persuaded,
is very true; because it is plainly a vegetable, as appears from his
own exact drawing of it; and seems to be the _fucus teres rubens minus
in longnum protensus_ of Ray’s Synopsis, ed. 3. p. 91. N. 53. This is
one of his principal arguments to prove the vegetation of corallines.
Tab. VIII. fig. 1. he calls a branch of red coralline; and at fig. 2.
he has it magnified, where it appears to be a geniculated red conserva,
drawn and painted with great exactness.
These arguments, my Lord, and these figures of real vegetables, which
the Doctor has given us for corallines, shew, how much he is willing to
support the old opinion of the botanists: but I am satisfied he will
soon alter his opinion, when he observes the remarkable difference of
the texture of vegetable and coralline bodies, when viewed in sea-water
thro’ a good aquatic microscope. And to convince him more fully, that
corallines are an animal substance, let him burn them, and he will
perceive the same pungent volatile alkaline smell, which he finds in
burning horn, hair, or oysters; whereas burnt fucus’s and conservas
yield a smell not much unlike that of common land vegetables. Even the
stony corallines, when their cretaceous covering has been dissolved in
vinegar, the membranous part, that remains of them, put into the fire,
yields the same animal smell with other corallines.
Further, since I find the Doctor has promised the Royal Society to
continue his researches at the seaside, the following hints may be of
use to him. And, first, he will find, that those he seems to think
naked polypes, which he found adhering to corallines and other bodies,
are really small corallines and escharas, with their proper skins
and cells; all which I have particularly described already. I would
then recommend him to examine such corallines as are taken out of the
deepest water, which are found adhering to shells and fucus’s. He will
find Mr. Cuff’s aquatic microscope, or one of that form, the most
commodious for observing these animals alive.
The most transparent ones he will find the best to discover their
gelatinous inside, which runs thro’ the stem and ramifications, and
ends in the heads, where the claws are. Some of the best kinds to
observe are as follows: The sea-oak coralline, the lily-flowering
coralline, the great tooth coralline, the sea-thread coralline, and
the branched tubular coralline. Pieces of these should be cut off
while they are in the sea water, and placed in watch-glasses full
of the same: in these they should remain a while, till they recover
themselves; and when they are placed on the stage of the microscope,
the motion of the internal part communicating with the heads will be
easily discovered.
If the Doctor will immerse some of these corallines, when they are
extended, in two thirds of spirit of wine and one third of clear
sea-water, it will preserve them many years, as I have experienced. He
may then put the different sorts into distinct phials, and view them at
pleasure with a lens of about one inch and half focus.
In fine, my Lord, opportunities so seldom offer at the sea-side to make
these experiments with accuracy; and likewise to this, the strong lines
of vegetation that these bodies carry in their appearance, and your
Lordship will not be surprised, that there are so many gentlemen, even
of the Royal Society, that totally disbelieve them to be animals.
Many there are in the Society, that are wavering between both opinions.
If then, my Lord, you think, that any specimens which I have, or any
demonstrations tending to clear up this point, that lie in my power,
will be acceptable to your Lordship and the Society, your Lordship may
freely command them, whenever you think proper, from
Your +LORDSHIP’S+
Much obliged and most obedient Servant,
John Ellis.
London, June 9. 1757.
XXXIV. _An Account of an extraordinary Operation performed in the
Dock-Yard at_ Portsmouth: _Drawn up by Mr._ John Robertson, _F.R.S._
[Read May 26, 1757.]
THE Royal William, a first rate man of war, built about 40 years ago,
having, upon examination, been judged in so good a state, as to be
worthy of repairing for sea service, was ordered into dock, and brought
thither on the 29th of June 1756. On these occasions it is usual to lay
across the middle line of the bottom of the dock, at distances of about
five feet from one another, thick pieces of oak timber of about four
feet long; their upper surfaces lying in the same plane, or so posited,
that a line stretched from the two extreme blocks will touch all the
intermediate ones; and on the middle of these blocks the keel of the
ship is to rest. On the said day the tide did not rise so high as was
expected; and there was not quite depth enough of water to float the
ship in, and set her on the blocks, notwithstanding the assistance of
an empty lighter, which, being fixed to the stern, lifted the ship at
the end six inches: and as the officers knew they should not have so
much water again before the next spring-tides, they were determined to
heave her in; which is a very common operation in most dock-yards. Now
it so happened, thro’ the great weight of the head and stern, that the
ship cambered very much; that is, her keel, from being straight, was
become much curved, the two extremities hanging lower than the middle
part by many inches; and consequently the foremost part of the keel,
instead of sliding over the blocks, forced all the foremost ones away,
for above 60 feet; whereby that part of the keel rested on the bottom
or floor of the dock, and the aftermost part rested on such of the
blocks, as had escaped the violence, which had displaced the others.
In this situation the keel was very far from being strait; and so it
was resolved to lift by main force the head of the ship, until the keel
should be strait; and in that position to support it by the blocks,
which had been forced away from their places.
For this purpose there were set up, under the wales and other parts of
the ship, to the length of near 80 feet of the stem, as many shoars,
as were judged necessary; and also nine pair of bed-screws, three pair
under each bow, and three pair under the knee of the head. At each
shoar a workman was appointed, to drive wedges between the heels of
the shoars and the parts of the dock whereon they rested; whereby the
shoars were raised end-wise, and consequently the body of the ship
lifted at the same time. While this was doing, the 18 screws were also
at work: and between these efforts the fore part of the ship was raised
upwards of 19 inches, so much being necessary to bring the fore part of
the keel in a right line with the hinder part.
In this service were employed about 270 men; whereof about 144 worked
at the screws, and the others worked at the shoars with their mawls and
wedges; and the whole operation was performed in about seven hours.
My curiosity leading me to inquire what was the weight of the ship,
in the condition she was at the time of bringing her into the dock;
for this purpose I procured draughts of the elevation and section, and
of the plans at the line of floating, and at the parallel sections
of every foot distance down to the keel. Then, by finding the mean
area between every two sections, I was thereby enabled to come at the
magnitude of a solid, that would nearly fill the trough the ship made
in the water; and, by increasing this magnitude by that of the keel,
and so much of the stern-post and stem, as were under water, the cubic
feet of the fluid displaced by the ship were obtained, being 54869;
and consequently her weight was 3532091 pounds, or 1576 tons, 16 _C_.
2 qrs. 3 ℔. These numbers were not altogether so easily come at, as
they would have been, had the ship swam on an even keel, her draught
of water before being 13 feet 2 inches, and abast 16 feet 6 inches.
However, the computation may be esteemed as correct as the nature of
the subject would admit; because I found pretty near the same solidity
by another method.
I got a block or model made, by a scale of a quarter of an inch to a
foot, of so much of the Royal William’s body, as was immerged, when
she was brought into dock; and this block I immersed in a trough of
sea-water, and found its weight in the following manner.
The length of the trough was 46 inches, breadth 14 inches, and
depth 8 inches: at each corner was a graduated scale of inches, and
pencil-lines drawn round the inside of the trough at every inch.
Sea-water was poured into the trough to the height of 5 inches; and
the trough was exactly levelled, by means of the pencil-line, at 5
inches: then the block being forced under the water’s surface, the
fluid, when still, was risen to 6⅓ inches; consequently the magnitude
of the block was equal to a parallelopipedon of 46 inches long, 14
inches broad, and 1⅓ inches deep, or to 858⅔ cubic inches.
Now 858⅔ cubic inches are equal to 0.4969 cubic feet.
And a cubic foot of sea-water weighs 64.373² pounds avoirdupoize.
Then 64.373² × 0.4969 = 31.987 pounds.
So that by a quarter inch scale, a model similar to the Royal William
weighs near 32 ℔.
But a quarter inch scale is ⅟48 of a foot scale.
And the model is to the ship as 1³ is to 48³, or as 1 is to 110592.
Then 3537506 ℔. (= 110592 × 31.987), or 1579 tons, 4 _C._ 3 qrs. 14 ℔.
is the weight sought.
The difference by the two methods amounts to 5415 ℔. or to 2 tons, 8
_C._ 1 qr. 11 ℔.
Some of the persons present at this experiment read the height of the
water at 6⅜ inches: the difference between 6⅜ and 6⅓ inches is ⅟24 of
an inch; a difference easily to be made by different persons in an
experiment of this kind. But observing, that the computation made on
6⅜ inches amounted to near 50 tons more than on 6⅓ inches, I caused
the trough to be diminished in its depth to 6½ inches, had one of the
ends cut off, and a board fixed on the open side, being desirous of
making the experiment with the trough standing on one end: and indeed,
in this situation, an error of ⅒ of an inch in the height of the water
makes a difference of about 16½ tons in the weight of the ship. Into
this upright trough water was poured to the height of 36 inches; and
the block being immerged, the water was raised 9⅓ inches: so that the
block was equal in magnitude to a parallelopipedon of 14 inches long,
6½ inches wide, and 9⅓ inches deep, or to 849⅓ cubic inches: from
whence I find the weight of the ship to be 1562 tons, 1 _C._ 2 qrs. 16
℔. And altho’ I take this number to be nearest the truth, yet it may be
observed, that it is no easy matter to come at accuracy in this subject
by any of the methods in common use.
My next inquiry was, to find how much of this weight was lifted, and
how to proportion it among the screws and mawl-men: but in this, less
accuracy must be expected than in the preceding inquiry; for the exact
number of men employed is not known; neither can it be told, how many
worked at the screws, and how many with the mawls; and only a guess can
be made at the part lifted. However, something may be gathered, which
may, perhaps, be worth the knowing.
Let the weight raised be taken at half the weight of the ship; for
64 feet, the length of the keel raised, is not far from half the
whole length: add to this the sally of the head, the weight of the
forecastle, the friction of the timber, and the resistance of the parts
bent by the cambering: beside, the mawls worked at several shoars set
up abast the said 64 feet.
Now the weight by the last experiment was 3499064 pounds: one half, or
1749532 ℔. I take to be the weight raised between the screws and mawls.
The distance between two contiguous threads of each screw was 1⅓
inches; the length of the two opposite levers was 12 feet 8 inches, or
152 inches, and described a circumference of 477½ inches: each screw
was worked by 8 men: their force, reckoned at 30 ℔. each, makes the
power working on each screw equal to 240 ℔.
Hence, from the known property, each screw could raise 65485 ℔.
And the 18 screws raised 1178730 ℔.
Then there remained 570802 ℔. to be raised among about 126 mawls:
Which gives 4530 ℔, or a little more than two tons, to be raised by
each man with his mawl and wedges; which is considerably less than what
I have seen raised by way of experiment.
XXXV. _Observations on an Evening, or rather Nocturnal, Solar_ Iris.
_By Mr._ George Edwards, _Librarian of the College of Physicians_.
_To the Reverend Dr._ Birch.
[Read June 16, 1757.]