Hence it appears that our atmosphere, when dry, is the agent by which we are enabled to accumulate electricity on non-electrics; as in the experiment before us, on the removal of it, the electricity passed off into the floor through a vacuum, of the greatest length we have hitherto been able to make, became visible in this vacuum, and manifested itselt by its effects on the air-pump, being the non-electric substance, which terminated that vacuum; whereas, when the air is not taken away, the dissipation of the electricity is from every part of the prime conductor. We see, also, contrary to what we have found hitherto, that an originally-electric body, viz. a dry glass tube, puts on the appearance of a non-electric, by becoming itself the conductor of electricity, that is, by its keeping out the air, and suffering the electricity to pervade the vacuum.

Mr. W. was desirous of knowing, for the further illustration of his propositions, whether the Leyden experiment could be made through the vacuum. For this purpose he made the before-mentioned exhausted tube part of the circuit, so necessary to this experiment. In this experiment it is absolutely necessary that the whole quantity, or nearly so, of the accumulated electricity, should be discharged in the same instant of time. Accordingly, on making the experiment, at the instant of the explosion a mass of very bright embodied fire was seen to dart from one of the brass plates in the tube to the other; but this did not take place when one of the plates was farther distant from the other than 10 inches. When the distance was greater, the fire then began to diverge, and lose part of its force; and this force diminished in proportion to its divergency, which was nearly as the distance of the two plates.

On Coral. By the Sieur de PEYSSONNEL, M.D.- [1751.]

M. DE PEYSSONNEL, in relation to the question, whether coral is a plant, according to the general opinion, or a petrification or congelation, according to some, after exhibiting the various arguments delivered in support of these, concludes that coral, as well as all other stony sea-plants, and even sponges, are the work of different insects, particular to each species of these marine bodies, which labour uniformly according to their nature, and as the Supreme Being has ordered and determined. The coral-insect [worm], which is here called a little urtica, purpura, or polype, and which Marsigli took for its flower, expands itself in water, and

contracts itself in air, or when you touch it in water with your hand, or pour acid liquors to it. This is usual to fishes or insects of the vermicular kind.

When our author was upon the coast of Barbary in 1725, he had the pleasure of seeing the coral-insect move its claws or legs; and having placed a vessel of sea-water with coral therein near the fire, these little insects expanded themselves. He increased the fire, and made the water boil, and by these means kept them in their expanded state out of the coral, as happens in boiling shell-animals, whether of land or sea. Repeating his observations on other branches, he clearly saw that the little holes perceptible on the bark of the coral were the openings through which these insects went forth. These holes correspond with those little cavities or cells which are partly in the bark, and partly on the substance of the coral; and these cavities are the niches which the insects inhabit. In the tubes, which he had perceived, are contained the organs of the animal; the glandules are the extremities of its feet, and the whole contains the liquor or milk of coral, which is the blood and juices of the animal. When he pressed this little elevation with his nails, the intestines and whole body of the insect came out mixed together, and resembled the thick juice furnished by the sebaceous glands of the skin. He saw that the animal, when it wanted to come forth from its niche, forced the sphincter at its entrance, and gave it an appearance like a star with white, yellow, or red rays. When the insect comes out of its hole without expanding itself, the feet and body of it form the white appearance observed by Marsigli; but being come forth, and expanded, it forms what that gentleman and our author took for the petals of the flowers of coral, the calyx of this supposed flower being the body of the animal protruded from its cell. The milk before mentioned is the blood and natural juice of the insect, and is more or less abundant in proportion to its health and vigour.

On the coast of Barbary, the fishermen brought him, in a barrel of sea-water, one of those madreporas which are called in Provence fenouille de mer, or sea-fennel. It had been put into the barrel as soon as it was taken out of the sea. and he observed, that the extremities of this madrepora were soft and tender, furnished with a transparent mucosity, like that of snails: these extremities were of a beautiful yellow colour, and were five or six lines in diameter. In this he saw an animal, resembling the cuttle-fish, polype, or seanettle. The body of this fish filled the centre: its head was placed in the middle of it, and was surrounded by several

feet or claws: these feet filled the intervals of the partitions observed in the madrepora, and were at pleasure brought to its head, and were furnished with yellow papillæ. Its head or centre was lifted up occasionally above the surface, and often contracted and dilated itself like the pupil of the eye. He had the pleasure of seeing it move distinctly all its claws, as well as its head or centre.

The flesh of the animal of the madrepora is so soft, that it divides on the gentlest touch. This soft texture prevented M. de P. from detaching any one; and he observes that there are in those seas several large species of urtica, which become soft on the least touch. He mentions one sort of above a foot in diameter, whose body is as large as a man's head, and which is of a poisonous nature. After the madrepora had been preserved three days, the contained animals covered its whole surface with a transparent jelly, which melted away, and fell to the bottom of the water as the animal died; and both the water and madrepora then had a putrid fishy smell. After having destroyed and consumed all the animals, the extremities of the madrepora became white.

From what has been extracted, concerning the coral and madrepora, an idea may be formed of the millepora, lythophyton, corallines, and sponges; each of which is, according to our author, the habitation of numerous animals, and formed by them. He has given, from his own observations, particular accounts of each of these productions, and divided them into genera and species with great accuracy; and though in common they are the habitations of animals, each species varying in form and bulk, and composing its cell in various forms and manners, and of different consistences, constitutes their essential character. As oysters, scallops, muscles, cockles, snails, &c. have a power given them, by the Author of nature, of forming and enlarging their separate dwellings, to these bodies, the subjects of this treatise, the same power is given, but in large families. In the madrepora, its animal occupies the extremity; in the millepora, the substance; in corallines and sponges, the void places; in coral and lithophytes, the cortical parts. Each of these animals, according to their kind, furnish substances differing as much in consistence as in form. That of coral is extremely hard, and compact; the madrepora and millepora are of a stony, but more loose texture; the coralline is still more soft; the lithophyton, of a substance nearer horn than stone; and the sponge is soft and elastic.

Letters of the Abbé Mazeas, F.R. S., on the Success of the late Experiments in France, concerning the Analogy of Thunder and Electricity.—[1752.]

THE Philadelphian experiments which Mr. Collinson communicated to the public having been univerally admired in France, the King desired to see them performed. Therefore the Duke d'Ayen offered his Majesty his country-house at St. Germain, where M. de Lor, master of experimental philosophy, should put those of Philadelphia in execution. His Majesty saw them with great satisfaction, and greatly applauded Messieurs Franklin and Collinson. These applauses of his Majesty having excited in Messieurs de Buffon, D'Alibard, and De Lor, a desire of verifying the conjectures of Mr. Franklin, on the analogy of thunder and electricity, they prepared themselves for making the experiments.

M. d'Alibard chose for this purpose a garden situated at Marly, where he placed on an electrical body a pointed bar of iron, of 40 feet high. On the 10th of May, 20 minutes past two, afternoon, a stormy cloud having passed over the place where the bar stood, those that were appointed to observe it drew near, and attracted from it sparks of fire, perceiving the same kind of commotions as in the common electrical experiments. M. de Lor, sensible of the good success of this experiment, resolved to repeat it at his house in the Estrapade at Paris. He raised a bar of iron 99 feet high, placed on a cake of resin, two feet square, and three inches thick. On the 18th of May, between four and five in the afternoon, a stormy cloud having passed over the bar, where it remained half an hour, he drew sparks from the bar. These sparks were like those of a gun, when, in the electrical experiments, the globe is only rubbed by the cushion, and they produced the same noise, the same fire, and the same crackling. They drew the strongest sparks at the distance of nine lines, while the rain, mingled with a little hail, fell from the cloud, without either thunder or lightning; this cloud being, according to all appearance, only the consequence of a storm, which happened elsewhere. From this experiment they conjectured, that a bar of iron, placed in a high situation on an electrical body, might attract the storm, and deprive the cloud of all its thunder.

St. Germain, July 12. 1752.-Towards 11 in the morning the heavens began to be covered to the south-west, with some claps of thunder and lightning at a great distance. The Abbé had just time to go to the garden, where he found the

Duke d'Ayen, who had prepared every thing for the experiments. An iron wire descended from the top of the pole, and rested on the hot-house of the garden: this wire was supported by a silken cord, and was terminated by a tin cylinder, of about three inches diameter, and three feet long. The electricity of this cylinder was such that, when a finger ap.. proached it, two or three very lively sparks at a time were produced, with a noise like that of the nails of one's fingers cracked against each other. Then the Duke d'Ayen took the first shrub he met in the hot-house, which happened to be that from which the labdanum is produced: he placed it with its pot on a cake of resin, and fastened the iron wire to one of its branches. This shrub was instantly electrified, so that whitish sparks issued from every leaf, with the same kind of cracking just mentioned; but the trunk of this shrub had a much stronger electricity; whether at that instant the electricity of the cloud was more strong (for it varies every moment), or that the force of the whole electricity, expanded through the leaves, became concentrated in the trunk of this shrub. The Duke then took one of his silver watering-pots, which was two feet and a half high: he filled it with water within an inch of the brim, and placed it on the electrical cake, dipping into it a wire of lead, which communicated with that wire which came from the top of the pole. Of all the electricity tried till then, this was incomparably the strongest: there were 20 sparks; and on advancing the finger towards it, the shock affected the arms and breast with great violence.

Letter from BENJAMIN FRANKLIN, Esq. concerning an Electrical Kite. Dated Philadelphia, October 1. 1752.

As frequent mention is made in the public papers from Europe, of the success of the Philadelphia experiment, for drawing the electric fire from clouds by means of pointed rods of iron erected on high buildings, &c. it may be agreeable to the curious to be informed, that the same experiment has succeeded in Philadelphia, though made in a different and more easy manner, which any one may try, as follows : —

Make a small cross, of two light strips of cedar; the arms so long, as to reach to the four corners of a large thin silk handkerchief, when extended: tie the corners of the handkerchief to the extremities of the cross: so you have the body of a kite; which being properly accommodated with a tail, loop, and string, will rise in the air like those made of paper; but this, being of silk, is fitter to bear the wet and