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similar to water-spouts, but without the capability of producing any visible agitation of the atmosphere, owing to their extreme subtilety. As the ocean presents an extended surface, I think it probable that in some cases these ascending columns are very large ; and when they intervene between a vessel and the land, the effect must be very strong, and consequently the more deceiving. I presume this is that kind of illusion which is familiar to seamen when they approach the land, and which, in nautical language, is denominated looming.
It somtimes happens, during the prevalence of a fog in the bay of New York, that objects present themselves to the eye seemingly very large, but which on a near approach are found to be of inconsiderable magnitude. I never beheld a case, however, in which the illusion made the object to appear so disproportioned and striking as the one mentioned by Mr. Jefferson.* The difference most probably arises from difference of situations.
The real cause of the deception I take to be this : After the sun has attained considerable altitude, and by its influence has dissipated the denser part of the vapor, the rays of light and heat penetrate through the remaining portion, producing a strong magnifying effect; and when, under these circumstances, an object is placed within a certain distance of an observer, (but of the real distance required to produce the effect, I am unable to speak,) it assumes a very imposing aspect, seeming to be much larger than it really is. I think I am correct in asserting, (and to this sentiment I attach great weight,) that none of these phenomena were ever noticed either before the sun had risen or after it had set. Hence I infer, that their true origin and cause must be traced to the influence which light and heat are generally understood to have on vapor; and which, under some circumstances communicate to it a high magnifying, and under others a bright reflecting property.
In relation to the singular circumstance of a mountain in Virginia assuming various and apparently whimsical shapes at certain periods, it can, in my view of the subject, arise from no other conceivable causes but from those at present under view. As before observed, ordinary evaporation is so extremely subtile as to elude our vision ;
* 'Having had occasion to mention the particular situation of Monticello for other purposes, I will just take notice that its elevation affords an opportunity of seeing a phenomenon which is rare at land, though frequent at sea. The scamén call it looming, Philosophy is as yet in the rear of seamen, for so far from having accounted for it, she has not given it a name. Its principal effect is to make distant objects appear larger, in opposition to the general law of vision, by which they are diminished. I knew an instance at Yorktown, from whence the water prospect eastwardly is without termination, wherein a canoe with three men at a great disiance, was taken for a ship with its three masis. I am little acquainted with the phenomenon as it shows itself al sea; but at Monticello it is familiar. There is a solitary mountain about forty miles off, in the south, whose natural shape, as presented to view there, is a regular cone; but by the effect of looming, it sometimes subsides almost wholly into the horizon; sometimes it rises more acute and more elevated; sometimes it is hémispherical ; and sometimes its sides are perpendicular, its top flat, and as broad as its base. In short, it assumes at times the most whimsical shapes, and all these, perhaps, successively in the same morning. Refraction will not account for this metamorphosis; that only changes the proportions of length and breadth, base and altitude, preserving the general outlines. Thus it may make a circle appear eliptical, raise or depress a cone; but by none of its laws, as yet developed, will it make a circle appear a square, or a cone a sphere.'
Notes on Virginia.
nevertheless, it must at times be of sufficient density to conceal a distant object from view. It is known that the atmosphere in high situations is generally cool; and fog is frequently seen extended in thin horizontal strata on the top of a ridge, becoming visibly condensed on meeting with the cool air above. The effect on invisible vapor we must presume to be the same ; and at times a body of it must be supposed to take the same place, remaining for a while stationary, (subject nevertheless to very sudden and material changes) concealing the top of the ridge from the sight. At the same time, streams of vapor are supposed to ascend from the foot of the ridge, and adhering to its sides in columns or some analogous shape, leave the prominent part exposed to the view of the observer. Sometimes these exhalations ascend in right lines, and coming in contact with the horizontal strata above, it gives to the mountain a quadrangular figure. At other times they are presumed to follow its sides, and meeting on the top in curved lines, it presents a hemispherical figure. And whatever may be the form assumed by the object, whether quadrangular, hemispherical, conical, sunk in the horizon, or whatever else, I feel well assured it is all the effect of the same law. In my opinion it can neither be traced to, nor can it originate from, any other conceivable or assignable cause.
It is remarked of the mountain in question, that it is isolated and solitary, and of a conical form. To this circumstance alone must be owing the exhibition of the strange phenomenon. I venture to assert, that no corresponding appearances were ever observed on a mountain of any considerable continuity, unless aided by distance and some peculiar circumstances, provided its shape and figure possessed the character of uniformity.
Since the foregoing observations on looming were written, I am altogether satisfied of their correctness, and do not now offer them as mere matter of speculation. Any person who wishes to remove from his mind every doubt in this respect, can easily do it. There is one state of the atmosphere alone in which this phenomenon is visible; and this is not unfrequent in the spring and autumn. In summer or winter it is rarely seen.
Whenever a sudden transition takes place from a warm or sultry, to a refrigerative atinosphere, this phenomenon is very visible at the north point of Staten Island ; at the Narrows; and at Weehawk, as before stated. The effect is produced solely by action between the two elements, air and water. The air in such cases being dry, and considerably colder than the water, a powerful evaporation immediately ensues ; for the plain reason, that an equilibrium in the operations of nature must be kept up; but, as I have already remarked, it cannot be seen until the light acts strongly upon it. Hence it will be found, that it is scarcely perceptible either before sunrise or after sunset.
It will be evident to every observer who is willing to examine for himself, that in a mere ordinary state of the atmosphere, the ridge in New Jersey, as seen through the Narrows, presents an almost even line of considerable elevation. In a few instances, I have perceived
An Oak by the Way-side.
the effect of looming to be so strong, that, in the language of Mr. Jefferson, it had almost 'subsided in the horizon. The comb of the ridge only was perceptible, and presented the appearance of small tufts or points.* This, I think, goes to confirm the suggestion before made, that the vapor ascends in columns. The very jagged appearance of those parts of the ridge, seen under such circumstances, I deem conclusive on this point. The steam from boiling water takes that shape, and still farther illustrates the position.
If Mr. Jefferson had taken pains to note the state of the atmosphere, during those periods when the mountain of which he speaks presented those whimsical appearances, I am well persuaded that he would have found them at no time visible, except during the prevalence of such a state of the atmosphere as I have mentioned. Indeed I hesitate not to say, that the principles of philosophy will authorize no other conclusion. And whether on land or on water, the effect is the same, since it must be owing to the same cause. The most skeptical can satisfy themselves in relation to this matter, with very little trouble.
In my next number, I shall present some facts in relation to the transmission of sound through the air, and offer a theory of thundershowers, and of west and north-west winds.
AN OAK BY THE WAY-SIDE.
Thou rear'st aloft thy giant limbs, as if to grasp the skies,
And hark! a shout sounds o'er the hill!- they come, the urchin-rout,
Hadst thou but kept thy forest-haunts, contented with the rest
Alone! - alone, a withered iree, upon the chill way-side!
* I have several times since remarked the fact, that the ridge mentioned above was wholly invisible, and that too in au upusually serene state of the atmosphere, which, however, was highly refrigerative. VOL. XI.
BY THE AUTHOR OF ‘ERATO,' AND OTHER POEMS.
"ANOTHER, AND ANOTHER!' — Hoary Time!
But Nature, in her visible works, doth far
Again – again:
What! – mirth,
And 'tis well:
On with the dance, then, and the harmless rout!
Ye shall abide for ever!
W. D. G.