« ZurückWeiter »
these, with my explanation of them, will afford you some entertainment.*
In answer to your several inquiries. The tubes and globes we use here, are chiefly made here. The glass has a greenish cast, but is clear and hard, and, I think, better for electrical experiments than the white glass of London, which is not so hard. There are certainly great differences in glass. A white globe I had made here some years since, would never, by any means, be excited. Two of my friends tried it, as well as myself, without success. At length, putting it on an electric stand, a chain from the prime conductor being in contact with it, I found it had the properties of a nonelectric; for I could draw sparks from any part of it, though it was very clean and dry.
All I know of Domien is, that by his own account he was a native of Transylvania, of-Tartar descent, but a priest of the Greek Church; he spoke and wrote Latin very readily and correctly. He set out from his own country with an intention of going round the world, as much as possible by land. He travelled through Germany, France, and Holland, to England. Resided some time at Oxford. From England he came to Maryland; thence went to New England; returned by land to Philadelphia; and from hence travelled through Maryland, Virginia, and North Carolina to you. He thought it might be of service to him, in his travels, to know something of electricity. I taught him the use of the tube, how to charge the Leyden phial, and some other experiments. He wrote to me from Charleston, that he lived eight hundred miles upon electricity; it had been meat, drink, and clothing to him. His last letter to me was, I think, from Jamaica,
• See page 330, for the paper here mentioned.
desiring me to send the tubes you mention, to meet him at the Havana, from whence he expected to get a passage to La Vera Cruz; designed travelling over land through Mexico to Acapulco; thence to get a passage to Manilla, and so through China, India, Persia, and Turkey, home to his own country; proposing to support himself chiefly by electricity. A strange project! But he was, as you observe, a very singular character. I was sorry the tubes did not get to the Havana in time for him. If they are still in being, please to send for them, and accept of them. What became of him afterwards, I have never heard. He promised to write to me as often as he could on his journey, and as soon as he should get home after finishing his tour. It is now seven years since he was here. If he is still in New Spain, as you imagine from that loose report, I suppose it must be that (hey confine him there, and prevent his writing; but I think it more likely that he may be dead.
The questions you ask about the pores of glass, I cannot answer, otherwise than that I know nothing of their nature; and suppositions, however ingenious, are often mere mistakes. My hypothesis, that they were smaller near the middle of the glass, too small to admit the passage of electricity, which could pass through the surface- till it came near the middle, was certainly wrong. For, soon after I had written that letter, I did, in order to confirm the hypothesis, (which indeed I ought to have done before I wrote it,) make an experiment. I ground away five-sixths of the thickness of the glass, from the side of one of my phials, expecting that, the supposed denser part being so removed, the electric fluid might come through the remainder of the glass, which I had imagined more open; but I found myself mistaken. The bottle charged as well after the
VOL. V. DD
grinding as before. I am now, as much as ever, at a loss to know how or where the quantity of electric fluid, on the positive side of the glass, is disposed of.
As to the difference of conductors, there is not only this, that some will conduct electricity in small quantities, and yet do not conduct it fast enough to produce the shock; but, even among those that will conduct a shock, there are some that do it better than othersMr. Kinnersley has found, by a very good experiment, that when the charge of a bottle hath an opportunity of passing two ways, that is, straight through a trough of water ten feet long, and six inches square, or round about through twenty feet of wire, it passes through the wire, and not through the water, though that is the shortest course; the wire being the better conductor. When the wire is taken away, it passes through the water, as may be felt by a hand plunged in the water; but it cannot be felt in the water Avhen the wire is used at the same time. Thus, though a small phial containing water will give a smart shock, one containing the same quantity of mercury will give one much stronger, the mercury being the better conductor; while one containing oil only, will scarce give any shock at a)l.
Your question, how I camei firgt to think of proposing the experiment of drawing down the lightning, in order to ascertain its sameness .with the electric fluid, I cannot answer better than by giving you an extract from the minutes I used to keep of the experiments I made, with memorandums of such as I purposed to make, the reasons for making them, and the observations that arose upon them, from which minutes my letters were afterwards drawn. By this extract you will see, that the thought was not so much "an out-of-the-way one," but that it might have occurred to an electrician.
"November 1th, 1749. Electrical fluid agrees with lightning in these particulars. 1. Giving light . 2. Color of the light. 3. Crooked direction. 4. Swift motion. 5. Being conducted by metals. 6. Crack or noise in exploding. 7. Subsisting in water or ice. 8. Rending bodies it passes through. 9. Destroying animals. 10. Melting metals. 11. Firing inflammable substances. 12. Sulphureous smell. The electric fluid is attracted by points. We do not know whether this property is in lightning. But since they agree in all the particulars wherein we can already compare them, is it not probable they agree likewise in this? Let the experiment be made."
I wish I could give you any satisfaction in the article of clouds. I am still at a loss about the manner in which they - become charged with electricity; no hypothesis I have yet formed perfectly satisfying me. Some time since, I heated very hot a brass plate, two feet square, and placed it on an electric stand. From the plate a wire extended horizontally four or five feet, and, at the end of it, hung, by linen threads, a pair of cork balls. I then repeatedly sprinkled water over the plate, that it might be raised from it in vapor, hoping, that, if the vapor either carried off- the electricity of the plate, or left behind it that of the water, (one of which I supposed it must do, if, like the clouds, it became electrized itself, either positively or negatively,) I should perceive and determine it by the separation of the balls, and by finding whether they were positive or negative; but no alteration was made at all, nor could I perceive that the steam was itself electrized, though I have still some suspicion that the steam was not fully examined, and I think the experiment should be repeated. Whether the first state of electrized clouds is positive or negative, if I could find the cause of that, I should be at no loss about the other; for either is- easily deduced from the