of Staffa, off the west coast of Scotland, composed of pillared basalt, there is the grand Cave of Fingal ; and in the basalt rocks at BertrichBaden, there is the very curious Grotte des Fromages, the basaltic columns of which have been so worn by the atmosphere, as to resemble a pile of cheeses, after which the locality has been denominated. In the vicinity of Quito, cavern formations occur in modern porphyry; and, upon a small scale, they are found in the lava of Vesuvius, ejected during the last few centuries. They are also common in Icelandic lavas, and in several cases are of prodigious magnitude.

Nothing is more incorrect than the idea, that the Master-hand has been exerted at random in moulding the globe, or that " an enemy hath done this," opposing the primal design, inferred from the confused and shattered condition of the superficial formations. There is wise contrivance in the apparently chaotic disorder; and benevolent purpose to be traced in the wild, convulsed, and seemingly unsystematic frame of the earth. Had its face been without the derangements which appear like faults in its constitution, there would have been no foundation for the facts thankfully recognised in the psalm:

"The springs arise among the valleys,
They run among the hills.

There the thirsty wild beast cools itself,
The wild ass quenches his thirst.

The fowls of heaven dwell beside them,
And sing among the branches."

Owing to the displacement of strata, creating chinks, rents, and cavernous sites, channels are prepared, through which the rains can percolate into internal reservoirs, where they are filtrated from the earthy admixtures taken up on their passage, and are again returned to the surface at a lower level by the same machinery in the form of springs. The end of material arrangements is not always apparent to us, but this is the exception, and not the rule. The design is clearly developed in an immense preponderance of instances, and it is one of obvious importance. Revelation gives the true interpretation of terrestrial nature in the saying, "The earth is full of the riches of the goodness of the Lord;" and as the advance of knowledge has shown what were simply viewed as dreadful phenomena, in ages of ignorance, to be necessary conditions, a just foundation is laid in this fact for the confidence, that, behind the dark clouds of Providence in the Christian life, there is the light of gracious intention to be eventually made manifest.

CHAPTER IV.

NATURAL HISTORY OF CAVERNS.

Causes of change-Power of water-Action of waves-Souffleur in the Mauritius-Staffa-Fingal's Cave-Basaltic columnsSir Joseph Banks-Maculloch-Sir W. Scott-Formation of columnar basalt-Experiment by Mr. Watt-Basalt on the Columbia river-Scripture epochs of terrestrial change Caverns in lava currents-Iceland-Dr. Henderson-Surtshellir Scandinavian mythology-Solid contents of lava streams-Eruption of the Skaptar-Yökul-Table-land of Quito -Remarkable mountain music-Heard by Humboldt-Heard in Arabia-Petræa-In the Pyrenees-Subterranean noises in Mexico-Representations of Scripture.

FROM testimony and from observation we have evidence of the fact, that, within the period of authentic history, the surface of the earth has undergone alteration, and is at present subject to a process of constant change. With the same truth we might speak of the fashion of this world passing away, in a physical sense, alluding to vicissitude in the features of inanimate nature, as we adopt that language to express the transitions of society, the succession of one generation of men after another, and the decay which surely awaits the monuments of their power and glory. Natural causes-some

incessant in their operation, general in their sphere, but very slow in producing any marked effect; others, occasional in their working, limited to particular districts, but acting with tremendous energy-combine to modify the contour of the globe, and sensibly to disturb its superficial form and lineaments. Reference is here made to the wearing influence of the atmosphere and the rains, "in breeze, or gale, or storm "-to the abrading and transporting power of streams and rivers, augmented by casual or periodical floods-to the action of the waves, tides, and currents of the ocean upon the coasts to the agency of excessive temperature, and of sudden changes of temperature -and to the violent forces exerted in earthquakes and volcanic explosions. These are instruments of change, which, during the comparatively short period in which physical events have been chronicled by enlightened nations, have affected the configuration of the earth, to whose agency it is now subject, and will be during the continuance of its present constitution.

.

s."

"The waters wear the stones."*

Impression,

in course of time, is made upon the most com

*Job xiv. 19.

pact mass of rock, by the constant fall of a few drops of water upon it; and the level slab gradually assumes a basin-shaped appearance, as if the mason's chisel had been at work upon it. Job introduces the physical fact as an image of the sure wasting of the strongest human frame under the wear and tear of time, alluding also to the action of a river in flood upon the adjacent country, as an illustration of the effect of the stream of years upon the life that now is:

"As the waters wear to pieces the stones,

As their overflowings sweep the soil from the land,
So consumest thou the hope of man."

Besides the effect here noticed, well expressed by Tyndale, "the floudes waste away the gravell and the earth," many remarkable examples occur of the power of running streams, at their ordinary flow, to carve out for themselves channels in the hardest rocks by gradual erosion. In this way masses of basalt in the volcanic region of central France have been invaded, and deep furrows cut through them by the rivers of the district. We have here one part of the machinery which has operated in the construction, enlargement, or modelling of cavern formations, very commonly connected with subterranean streams; and especially is