any other part of the house. To this end of the iron rod was fastened an iron chain, which was conducted into the chamber of Professor Richman, on electrics per se, so as no where to touch the building. The entrance to this chamber faced the north; and, at the south end of it there was a window, near which stood a table four feet in height. On this the professor placed his electrical gnomon, and connected it with the chain, which was brought under the ceiling of the room over this table, and communicated with the apparatus on the top of the house, by means of a wire which hung from the chain, and was joined there by a little ring, and communicated with the rod. When the iron rod at the top of the house was affected by the thunder, or otherwise suitable condition of the atmosphere, the thread before-mentioned deviated from the perpendicular; as it would also do, if artificially electrized. The Professor always observed a greater ascent of the thread from artificial electricity than by that from the atmosphere. By the former, he had seen it on the quadrant describe an angle of above 55°, but never above 30 by the latter. In the year 1752, August 9, the apparatus acquired so great a de. gree of electricity from the atmosphere, that from the end of the rod the electrical flashes might be heard at several feet distance. Under these circumstances, if any one touched the apparatus, they felt a sharp stroke in their hand and arm.

Professor Richman sometimes added to this apparatus a glass bottle of water, after the manner of Professor Muschenbroek, adapted to a vessel of metal placed on glass. The wire from the mouth of the bottle of water, during the time of the thunder, he caused to communicate with another wire. From this addition he found the electricity from the atmosphere more vehement than it was without it. This he first observed on May 31, 1753, when the electrical fire exploded with such a force, that it might be heard at the distance of three rooms from the appara. tus. On the left hand of the bottle was placed a second elec trical gnomon. When this was made use of, the wire of the one metal, and the wire of the other, were connected with a prime con. ductor from an apparatus for artificial electricity, viz. a glass globe, &c. At the same time also, from the chain was fastened a piece of wire in contact with the vessel. By these means, when the electrical machine was put in motion, both the electrical gnomons

were electrified: but this went off, in a great measure, as soon as the motion of the machine ceased. By this whole apparatus taken together, Professor Richman observed a kind of reciprocation in the effects of electricity; for at first, when the electrical machine was put in motion, both the linen threads arose with the degrees of their respective quadrants. If then the wire of the right gnomon was touched, the right-hand thread collapsed to the rod; but the thread on the left side continued diverging as before the touch. Also, if the wire of the left gnomon was touched, then in its turn the thread at the rod of the right gnomon col. lapsed, and the thread of the right gnomon ascended again. This reciprocation of the ascending and descending of the thread, might be repeated three or four times without exciting the ma. chine anew.

The ingenious and industrious Professor Richman lost his life on the 6th of August, 1753, as he was observing, with Mr. Sokolow, engraver to the Royal Academy at Petersburgh, the effects of As soon as electricity on his gnomon, during a thunder-storm.

his death was publicly known, it was imagined that the lightning was more particularly directed into his room by the means of his before-mentioned apparatus. And when this affair was more in. quired into, this opinion appeared to be not ill-founded; for Mr. Sokolow saw that a globe of blue fire, as large as his fist, jumped from the rod of the right gnomon, towards the forehead of Professor Richman, who at that instant was at about a foot dis. tance from the rod, observing the electrical index. This globe of fire, which struck Professor Richman, was attended with a report as loud as that of a pistol. The nearest metal wire was broken in pieces, and its fragments thrown on Mr. Sokolow's clothes, from their heat, burnt marks of their dimensions on them. Half of the glass vessel was broken off, and the filings of metal in it were thrown about the room. Hence it is plain, that the force of the lightning was collected on the right rod, which touched the filings of metal in the glass vessel. On examining the effects of lightning in the Professor's chamber, they found the door-case split half through, and the door torn off, and thrown into the chamber. The lightning therefore seems to have continued its course along the chain, conducted under the ceiling of the room; but that it came from the apparatus at the top of the house to the

door, and then into the chamber, does not, as far as can be recollected, appear.

If indeed it could be ascertained, that the lightning, which was the death of Professor Richman, was collected on the apparatus, for this reason, because these bodies, at the instant of the light. ning, were capable of attracting and retaining the electricity, it would then be in our power sometimes to divert the effects of lightning. But of this fact, more time and longer experience must acquaint us with the truth.

Hence Mr. Pinkney may acquaint Dr. Lining, that in Mr. Watson's opinion, at the time Professor Richman was killed, his apparatus was perfectly insulated, and had no communication with the earth, by the means of metallic or other substances, readily conducting electricity, and that the great quantity of electricity, with which, from the vastness of the cause, the apparatus was replete, discharging itself through the Professor's body, being the nearest non-electric substance in contact with the floor, and was unfortunately the cause of his death. This, it is presumed, would not have happened, had the chain, or any other part of the appa. ratus, touched the floor, by which the electricity would have been readily communicated to the earth.

Since the reading of the above to the Royal Society, a treatise in Latin, intitled, Oratio de Meteoris vi Electrica Ortis, by Mr. Lomonosow, of the Royal Academy of Sciences at Petersburg, has been transmitted to the Society. By this, among many other curious facts, we have been informed of certain particulars in re. gard to the death of Professor Richman; of which the following may not be improper to be inserted here.

Mr. Lomonosow observes, that with regard to the sudden death of the gentleman before-mentioned, the accounts, communicated to the public, contained some circumstances not fairly stated, and others of some importance were entirely omitted. With regard to the first, it is incontestably true, that the window, in the room where Professor Richman was, had continued shut, that the wind might have no effect on his electrometer; but that the window in the next room was open, and the door between these two rooms, was half open; so that the draught of air might justly be suspected to have followed the direction of the iron con. ductor of the Professor's apparatus; that his conductor came

from the top of the house, and was continued as far as necessary. Secondly. That his conductor was not placed far from that doorcase, part of which was torn off. Thirdly. That at this time no use was made of the Leyden bottle, mentioned in the preceding account; but the iron was inserted into a glass stand, to prevent the dissipation of the electrical power, and that the gnomon should show its real strength.

With regard to the second, there has as yet been no mention, that Professor Richman, at the time of his death, had seventy rubles (a silver coin) in his left coat-pocket, which by this accident were not in the least altered. Secondly. That his clock, which stood in the corner of the next room, between the open window and the door, was stopped; and that the ashes from the hearth were thrown about the room. Thirdly. That many persons without doors declared their having actually seen the lightning shoot from the cloud to the Professor's apparatus at the top of his house. In the Phil. Trans. is given a view of the chamber, where the Professor was struck by the lightning: who stood with his head projecting towards his electrometer; near stood Mr. Sokolow the engraver; from the door a piece was torn off, and carried forward; part of the door-case was also rent.

In this treatise Mr. Lomonosow, among other phænomena of electricity, takes notice, that he once saw, in a storm of thunder and lightning, brushes of electrical fire, with a hissing noise, communicate between the iron rod of his apparatus and the side of his window; and that these were three feet in length, and a foot in breadth. Effects like these no one but himself has had the opportunity of observing.

[Phil. Trans. 1754.

CHAP. XLIV.

ON MAGNETISM.

SECTION 1.

General Remarks on the Theory and Parts of Magnetism.

THE theory of magnetism bears a very strong resemblance to that

of electricity, and it must therefore be placed near it in a system of natural philosophy. We have seen the electric fluid not only exerting attractions and repulsions, and causing a peculiar distri bution of neighbouring portions of a fluid similar to itself, but also excited in one body, and transferred to another, in such a manner as to be perceptible to the senses, or at least to cause sensible effects, in its passage. The attraction and repulsion, and the peculiar distribution of the neighbouring fluid, are found in the phenomena of magnetism; but we do not perceive that there is ever any actual excitation, or any perceptible trausfer of the magnetic fluid from one body to another distinct body; and it has also this striking peculiarity, that metallic iron is very nearly, if not absolutely, the only substance capable of exhibiting any indications of its presence or activity.

For explaining the phenomena of magnetism, we suppose the particles of a peculiar fluid to repel each other, and to attract the particles of metallic iron with equal forces, diminishing as the square of the distance increases? and the particles of such iron must also be imagined to repel each other, in a similar manner. Iron and steel, when soft, are conductors of the magnetic fluid, and become less and less pervious to it as their hardness increases. The ground work of this theory is due to Mr. Aepinus, but the forces have been more particularly investigated by Coulomb and others. There are the same objections to these hypotheses as to those which constitute the theory of electricity, if considered as original and fundamental properties of matter; and it is additionally difficult