Beroe fulgens

In September, 1806, I took at Sandgate a number of the of various sizes. beroe fulgens, but no other species: they were of various dimensions, from the full size down to that of the medusa scintillans: they could however be clearly distinguished from the latter species, by their figure.

Medusa scintillans on various parts of our evasts.

Number of the

caught.

Since that time, I have frequently met with the medusa scintillans on different parts of the coast of Sussex, at Tenby, and at Milford haven. I have likewise seen this species in the bays of Dublin and Carlingford in Ireland.

In the month of April, last year, I caught a number of the beroe fulgens beroe fulgens in the sea at Hastings: they were of various sizes, from about the half of an inch in length, to the bulk of the head of a large pin. I found many of them adhering together in the sea; some of the larger sort were covered with small ones, which fell off when the animals were handled; and, by a person unaccustomed to observe these crcatures, would have been taken for a phosphoric substance. On putting a number of them into a glass, containing clear sea water, they still showed a disposition to congregate upon the surface. I observed, that, when they adhered together, diffused light they showed no contractile motion in any part of their body, which explains the cause of the pale or white colour of the diffused light of the ocean. The flashes of light, which I saw come from the sea at Herne bay, were probably produced by a sudden and general effort of the medusæ to sepa rate from each other, and descend in the water.

Cause of the

on the ocean,

and of the flashes in Herne bay.

Medusa scintil

Milford havent

The medusa scintillans almost constantly exists in the lans abounds in different branches of Milford haven, that are called pills. I have sometimes found these animals collected in such vast numbers in those situations, that they bore a considerable proportion to the volume of the water in which they were contained: thus, from a gallon of sea water in a luminous state I have strained above a pint of these meduse. I have found the sea under such circumstances to yield me more support in swimming, and the water to taste more disagree. ably than usual; probably the difference of density, that the density of has been remarked at different times in the water of the sea, may be referred to this cause.

Probably affect

the sea.

The most fre

All my own observations lead me to conclude, that the quent source of medusa scintillans is the most frequent source of the light the luminous

Mistaken for

of the sea around this country; and by comparing the ac- ness of the sea. counts of others with each other, and with what I have my the nereis nocself seen, I am persuaded, that it is so likewise in other parts tiluca by some; of the world. Many observers appear to have mistaken and described by others, who - this species for the nereis noctiluca, which was very natu- were not aware tural, as they were prepossessed with the idea of the fre- of its nature. quent existence of the one, and had no knowledge of the

other. Some navigators have actually described this species of medusa, without being aware of its nature. Mr. Bajon, during his voyage from France to Cayenne, collected many luminous points in the sea, which he says, when examined by a lens, were found to be minute spheres. They disappeared in the air. Doctor Le Roy, in sailing from Naples to France, observed the sparkling appearance of the sea, which is usually produced by the medusa scintillans. By filtering the water, he separated luminous particles from it, which he preserved in spirit of wine: they were, he says, like the head of a pin, and did not at all resemble the ne. Feis noctiluca, described by Vianelli; their colour approach. ed a yellow brown, and their substance was extremely tender, and fragile. Notwithstanding this striking resem blance to the medusa scintillans, Le Roy, in consequence of a preconceived theory, did not suppose what he saw were animals, but particles of an oily or bituminous nature *.

The minute globules, scen by Mr. Langstaff in the Indian ocean, were, I think, in all probability, the scintil lating species of medusa: and on my showing him some of these animals I have preserved in spirits, he entertained the same opinion.

Professor Mitchell, of New York, found the luminons appearance on, the coast of America, to be occasioned by minute animals, that, from his description, plainly belonged to this species of medusa, notwithstanding which, he supposed them to be a number of the nereis noctiluca +.

* Observ. sur une Lumière produite par L'Eau de la Mer. Mém. Etrang, des Sc.

Phil, Mag. Vol. X, p. 20.

The

The luminous animalcule of Forster.

Luminousness of the sea erroneously ascribed to various causes.

The luminous animalcule, discovered by Forster off the Cape of Good Hope, in his voyage round the world, bears so strong a resemblance to the medusa scintillans, that I am much disposed to believe them the same. He describes his animalcule as being a little gelatinous globule, less than the head of a pin; transparent, but a little brownish in its colour; and of so soft a texture, that it was destroyed by the slightest touch. On being highly magnified, he perceived on one side a depression, in which there was a tube that passed into the body, and communicated with four or five intes tinal sacs. The pencil drawings he made on the spot are in the possession of Sir Joseph Banks, by whose permission engravings from them are subjoined to this paper. By comparing these with the representations of the medusa scintillans, and some of this species rendered visible, by being a long time preserved in spirits, which I have laid before this learned society, it will be found, that the only difference between Forster's animalcule, and the medusa scintillans, is in the appearance of the opaque parts, shown in the microscopic views.

Many writers have ascribed the light of the sea to other causes than luminous animals. Martin supposed it to be occasioned by putrefaction: Silberschlag believed it to be phosphoric: professor J. Mayer conjectured, that the sur face of the sea imbibed light, which it afterward discharged. Bajon and Gentil thought the light of the sea was electric, because it was excited by friction. Forster conceived, that it was sometimes electric, sometimes caused from putrefac tion, and at others by the presence of living animals. Fougeroux de Bondaroy believed, that it came sometimes from electric fires, but more frequently from the putrefaction of marine animals and plants.

I shall not trespass on the time of the Society, to refute the above speculations; their authors have left them unsupported by either arguments or experiments, and they are inconsistent with all ascertained facts upon this subject.

(To be concluded in our next.)

III. Note

III.

Note on the Water contained in fused Soda. By Mr. J. : E. BERARD *. ***

MR. d'Arcet had found, that pure alkalis, after being Water in soda

fused, contained water, and he

estimated the quantity An analysis, which I made some time after in a different mode, gave me but18.86.

in soda as high as 28 per cent +.

after fusion.

soda different

The result of Mr. d'Arcet is founded on the analysis of Mr. d'Arcet the subcarbonate of soda. For this salt too he has given portions of subgives the proproportions different from those I found t. Not know. carbonate of ing the particulars of Mr. d'Arcet's experiments, Lascribed from the the difference of our results respecting the water in soda author, to the difference in these proportions. In confirmation of his opinion however, he has just published these experiments; and has made several objections to my method of and makes analysing the subcarbonate, which I shall endeavour to

remove.

to his method

He considers the solution in acids as an inaccurate mode; two objections. 1st, because the solution retains carbonic acid: 2dly, because the gas evolved carries off water with it.

It may be observed, that, these sources of errour being These errours opposite in their effects, they in great measure counteract tend to balance each other. each other but we shall see what is their extent. The The first must temperature amounts at most to 20° [68°F], when the be of very small amounts carbonate decomposed by the acid is already in solution. Now at this temperature water under the pressure of the atmosphere alone would not dissolve any thing like its own bulk of carbonic acid gas. But this quantity may be wholly neglected, when we consider, that a large ex cess of sulphuric acid is added, and the solution strongly. shaken.

Annales de Chim. vol. lxxii, p. 96.

† Ann. de Chim. vol. lxviii, p. 175; or Journal, p. 31 of the present vol.

For the component parts of different salts by Mr. Berard see Journal, vol. xxvi, p. 206.

As

and the same is

cond.

As to the water carried off by the gas, when the experitrue of the se- ment is performed with due caution in proper vessels, the gas only carries with it hygrometrical water. Now this quantity may easily be calculated. The gas in my experiment weighed 4-195 gram. [64-77 grs.]: consequently its volume, at 20° [68°F.] and 0.75 met. [29.5 in.] pressure, was 2.3 lit. [4.8 pints]; and the weight of the aqueous vapour 4.2 cent. [0.65 of a gr.]. If this quantity be diminished by the very small quantity of carbonic acid retained in the solution*, we shall have the extent of the errour, to which this analysis is liable; for the process is so simple, that on repeating it we obtain almost precisely the same quantities. I conceive it much to be wished, that all analyses were susceptible of this precision: besides, I have confirmed it by other experiments. I reduced the subcarbonate to muriate and sulphate, and the results I ob tained were found to agree with the analysis I had adopted. I now proceed to the objections which Mr. d'Arcet has made to my method of determining the water in soda, and which consist in this, that the component parts of muriate of silver are not accurately determined; and that this salt is soluble in the waters of elutriation.

Objections to the mode of determining the water in soda.

Proportions of muriate of sil

ver ascertained.

This muriate is among the most insoluble salts.

Chenevix, Zaboade, Proust, Bucholz, Rose, and others, have successively determined the proportions of muriate of silver. The quantity of acid contained in this salt varies in their results from 17 to 18. Rose and Bucholz make it 17.5, which is the proportion I have adopted. The late experiments of Gay-Lussac carry it to 18. When the proportions assigned to a salt vary only half a hundredth part, they may be fairly considered as ascertained.

With regard to the solubility of muriate of silver, I believe we may affirm, that it is one of the most insoluble salts employed in analysis, when the liquid is neutral and contains very little of any other salt. It even requires a pretty considerable excess of aeid, to dissolve any notable

There is still another circumstance, that tends to diminish the weight of the carbonic acid: this is, the gas evolved expels great part of the atmospheric air contained in the empty part, and takes its place.

· quantity