A Cave
The following brief description of a cave vulgarly called the "Devil's Hole,"lying in Durham Township, Bucks County, Pennsylvania, and about fifty miles north of Philadelphia, may not perhaps be unacceptable to some of your readers. The observations were made August 5th and October 12th, of the year 1802.It certainly ranks among the natural curiosities of this country and deserves greater publicity than that which has been given it by historians. Should some naturalist have recourse to the place, survey the cave, and give an authentic, minute, ample and animated account of it to the world, he would do no more than his duty.
The entrance into this grotto is about 100 yards west of the Delaware River, and from 150 to 200 (yards) north from the point of land at the confluence of Durham Creek and said river. The height of the eminence (hill/outcropping), enclosing the cavity, is from 200-230 feet above the level of the circumjacent land. From the pathway of the entrance to the top of the rock above, the measurement is upwards of 40 feet. Three or four persons may easily enter abreast; but no more, as the mouth, though wide enough for admitting a great number, is rendered inaccessible by a ledge of rocks running partly across.
The cave is naturally divided into three grand apartments, out of each of which into the other the decent is steep, caused also by rocks prominent and jutting. After a decent of about 30 feet, the first apartment or chamber, displays its greatest height and width, of which it is not an easy matter to form a true estimate, on account of the irregularities of the vault occasioned by deep interstices (crevices), and low dependent stone (breakdown blocks).
A faint idea of its dimensions may, however, be formed from the following statement.
October 12, 1802: In the open air the thermometer stood at 64 degrees(F), at the partition between the first and second apartments, it descended to 59 degrees. Between the second and third apartments it sunk to 54 degrees, which it preserved throughout the whole of the innermost chamber.
August 5, 1802: The thermometer was very differently affected by the enveloped air, standing then, in the open at 78 degrees(F), and at the lower end of the first chamber at 54, but at the farther end of the lowermost, rose to 62.
To account for the rising of the mercury at the bottom, I cannot concede to the hypothesis of either Mr. Bayle or Dr. Goldsmith, but must venture a conjecture of my own.
It is found by experience, that, in mines of great depth, the air, for a considerable space in the descent, grows colder, but afterwards, is felt to be of a warmer temperature increasing proportion ably with the depth, Mr. Bayle accounts for this by alleging "magazines of fire to be near the center of the earth, which communicate their heat to the neighboring regions." But Goldsmith ascribes it to other causes: "in some mines the composition of the earth all around is of such a nature, that upon the admission of water, or air, it frequently becomes hot, and often bursts out into eruptions. Beside this, as the external air cannot readily reach the bottom or be renewed there, an observable heat is perceived below, without the necessity of recurring to the central heat for an explanation."
In the instance of the mercury rising at the bottom of the cave, it is presumed that the air, being perceived warmer, originated from neither of the above causes, but from the heat of a numerous party who had been there a considerable time with lights, before the thermometer was applied. The depth is not great enough to reach Bayle's central fire; nor are there any evidences of Goldsmith's chemical operation between the air and mineral substance.
On some parts of the vault is a white parget somewhat crystallized, and is probably a petrifaction, composed of water exuded through the rock and calcerous matter.
Over other parts of the arch there is another kind of incrustation, dark in color. This has the appearance of moss upon a tree, but as hard as the rock itself, and over it water is continually trickling. The rock encompassing the cavern is entirely limestone, through which in many places, there is a perpetual percolation of water.
By supposition, the descent in a right line, forms an angle of 40 degrees with the horizon.
At the bottom is a basin of excellent water, which measured twenty feet to the place where it came into contact with the rock, terminating the cave as far as it has been or can be yet explored.
Beyond the meeting or the rock and water there is a conduit running farther into the earth, than could be measured with a long pole; and is, undoubtedly continued, through it may ramify into many subordinate channels, before it advances to the beds of the river and creek.
The many springs on the verges, the proportional rising and falling of the waters in the river and creek, demonstrate the connection and prove the surface of the one to get on a level with the other. When there is a high fresh in the river, the lower chamber is nearly filled.
At the partition between the first and second apartments a small branch of the cave, 32 feet in length, takes a course in an easterly direction and so wide as to permit in some places two persons to pass. From this branch are two others, still smaller, the one extending 22 feet north, the other 14 feet south, and in width admitting one person.