434 



PHYSICAL GEOGRAPHY. 



Volcano of Orizaba. 



small scale, by burying in the ground a moistened mixture of sulphur and iron filings, 

 when the mass becomes gradually heated, takes fire, and explodes. The lava which 

 flows out to the surface in volcanic eruptions, or is driven up in dust and scoriae, is owing 

 to the violent extrication, through a vent, of the steam which has been generated, 

 accumulated, and confined, the oscillations and heavings of the ground in earthquakes 

 being produced by the action of elastic vapours and gases endeavouring to effect their 



escape by a rending of the strata. Such 

 is the hypothesis. It requires the metal- 

 loids to exist in the interior of the earth, 

 and the admission of water in sufficient 

 abundance to them, a condition which may 

 be conceded, with strong probabilities in 

 its favour. It has been considered an 

 evidence supporting this theory, that 

 nearly all active volcanoes are situated 

 near the sea, or in ranges of mountains 

 which approach it at certain points, while 

 coast situations have been the foci of the 

 most terrible modern earthquakes, as those 

 of Lima, Lisbon, Messina, and Caraccas. 

 The extinct volcanoes of Auvergne and 

 the Catecucaumene are indeed apart from the present ocean, and this is true of several 

 sites of former volcanic action ; but in those ancient times, when " fire and vapour of 

 smoke" marked the panorama, the relative distribution of land and sea in those localities 

 might be different to what it is at present. 



It is difficult to form just views of events occasioning such calamities to the human race 

 as the reduction to instability of the before fixed and firm foundations of the globe. When 

 in a few passing seconds peaceful homes become the sepulchres of their inhabitants, and 

 the roof that long has sheltered them from inclement elements is the engine of their 

 destruction when scenes verdant through the industry of man are Converted into 

 frightful desolations, and cities fall, involving youth, beauty, and innocence in indiscriminate 

 ruin with proficient and inveterate vice men are prone to reflections questioning the 

 goodness and fitness of things, challenging the arrangements of the Creator in the scheme 

 of the creation. Yet in most cases this is the offspring of a miserable selfishness ; for 

 the same parties will gloat over a battle in which their nation has been victorious, though 

 destructive to more than ever perished by any one natural visitation of earthquake, 

 volcano, or pestilence ; the human action, at the same time, involving a deep moral guilt 

 which belongs not to the physical phenomena. It may be well to recollect, in relation to 

 these paroxysms of nature, that science and philosophy step in, and suggest relieving 

 considerations. They unfold the long antiquity of the earth, teach us to contemplate it 

 in connection with an era compared to which an age is a span, and unfold the tendency 

 of those milder agencies which are in incessant action upon it, and which, though slow 

 workers, would effect extensive and disastrous changes in the succession of centuries, if 

 there was no counteraction to them. Inequalities of the surface eminently adapt the 

 globe to be the residence of man during his threescore years and ten, and of the myriads 

 of different races of beings that inhabit it. But the waste of the elevated dry land is a 

 gradual yet sure effect produced by the atmospheric and aqueous causes that constantly 

 act upon it. These, without an antagonist power, would, in time, reduce the inequalities 

 of alluvial countries nearly to a uniform level, bring the habitable part of our planet down 

 to the ocean line, and convert scenes of fertility and busy life into vast lagunes and 



