Philosophical transactions, Vol. L. Part I. For the year 1757. · Various
TABULA DECIMA.
_Fig._ I. Tres species animalculorum lucentium in guttula aquæ marinæ fortiore microscopio visorum. _Fig._ II. Mirum animalculum in corallinis a doliis marinis coniformibus abrasis repertum. A. tales minores erant centeni. B. decem vel duodecim erant hac magnitudine naturali. C. idem animal microscopio visum. _a._ Antennæ. _b._ Primum par pedum vel brachiorum. _c._ Secundum par. _d._ Tertium et maximum par. _e_, _e_, _e_, _e_. Quatuor corpuscula oviformia, quæ animal ut movebat natando. _f_, _f_, _f_, _f_, _f_, _f_. Sex pedes posteriores, quibus simul corallinæ ramum arripiens, quaquaversum se flectore poterat. _g._ Cauda in cujus extrema parte anus. _h._ Oculi. _Fig._ III. Aliud animal in iisdem corallinis repertum. A. illud animal pronum. B. supinum. C. fortiore microscopio visum. _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.]
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