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Itances in folil bodies. By a diffolution of fernambuco wood, the doctor gives various colours to these petrifications. Thus these great interpreters of nature cannot help acknowledging the extreme promptitude of her actual processes on a small scale, whilst they disavow the possibility of a like celerity in her primæval powers of concretion on a larger ; because it would militate against their favourite system, of flow operations during an infinity of ages.

(dd) Page 376. It is well known that artificial stones, perfectly resembling in appearance and folidity Portland stone, have been long fabricated in London. Variegated alabasters, jaspers, and agates, are crystallized at 'Alhbourne and other places. The art of man has not yet been able to give their genuine lustre or falidity to the imitations of diamonds and the finer precious stones; but all other kinds of stones are imitated to a degree of perfect deception by a hundred artists in every part of Europe. Shall plastic Nature in her fullest vigour, the goddess whom some philosophers alone adore, or the omnipotent God of Nature herself, require thousands and ten thousands of years to complete the originals, however greatly they may surpass the imitations?

(ee) Page 377 The crystallization, or what is called the vegetation, of lead in water by zinc is but lately discovered. Sugar of lead in water is so powerfully and quickly attracted by a piece of zinc, that in a few hours the whole forms a beautiful arborization pendent in the bottle from that matter. Such crystallizations are also effected by fire. Mr. Ferber observes, that various shorl crystallizations are formed in the empty bubbles of the torrents of lava, cooling on the superficies whilst yet in violent fusion underneath. Diamond-like crystallizations are likewise formed in it, though much inferior in hardness, in regularity, and brightness of colours, to real gems which are crystallized in water. When the whole earth was yet a liquid pulp

swimming swimming in every kind of menftruum, actuated upon by the great mass of universal light, and when dry land appeared, by the full force of its ruling sun, how can we suppose that these fame laws of nature in their fullest vigour should require thousands of years to crystallize or coagulate the various substances of which we see it now composedWhat these wa. tery menstrua did not effect, frequent volcanic fires natural in the first great fermentation of matter, either immediately after the creation or after ihe deluge, when its exterior coat was nearly reduced to the same situation might well bring to perfection during the first four centuries, when men were yet confined to a narrow spot. That at this last epoch its whole exterior surface was convulsed, dislocated, and diffolved, every monument of nature amply testifies. God had said that he would destroy not only the whole impious race of men but the earth with them, and he afterwards promises Noah that there shall not be another deluge" dislipating," according to the literal words of the Hebrew; according to the Samaritan version “scattering,” or “ dispersing;” translated by the Greek “ to cor

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rupt," or "disfigure," and by the Syriac and Arabic “ to destroy the earth; that is to say, since the body of the globe remained, its outward form and surface.


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Various Opinions on the Nature of Light, Heat, and Firę.


AFTER having in my preceding letter laid before you the celebrated system of Mr. de Buffon, and the several opinions of many other modern philosophers tending with him to prove not only the high antiquity of this globe, but the numberless ages required to elaborate and consolidate its component parts, and to fashion its actual structure; and having given you with freedom my reafons for dissenting from their pretended irrefragable proofs of this thesis ; you will give me leave, previous to any further discussion on that subject, to say, with extreme diffidence, a few words on the nature of Light, Heat, and Fire. On this head natural philofophy, as yet in its infancy, is very undecided, and has produced a num


ber of discordant opinions. It is, however, a point which appears to me of great importance, and by no means indifferent for the settling of our ideas, both on the original and actual formation of this earth and on the continued operations of nature. Оа this difficult subject, I shall rather produce the different opinions of others than presume to offer any fixed sentiment of my own. Heat, Fire, and Light, have till very lately been generally looked upon as one and the fame matter, proceeding from one and the same cause, distinct only in degree--fire generated from heat, and light from fire. All three, however, appear

in many instances perfectly distinct, and discriminated by various and frequently opposite effects. The source of all three has been generally placed in the fun, or at least that body has been looked upon as their great magazine; but on this too there are different opinions.

It is on the basis of fire first existing in the fun and purloined from thence by other bodies that Mr. de Buffon has laid his system. Having once kindled and fixed it there as in its feat, he imagines whatever relics rernain of it in our planet to be no other than a Slackened portion thence originally derived. As we have already seen, he confiders not heat, fire, and light, deemed only different degrees from one and the same cause, as a distinct element from his fole vitreous substance. They are, according to him, purely generated from, and the effects of, pressure and friction. By their operation, without the intervention of any other distinct matter, the sun


was put and remains in fusion, and became a liquid mass of glass producing heat, fire, and light. The possibility of these emanating from his vitreous matter by mere pressure and friction we have already noticed, and left to his more fagacious disciples to explain. Had he allowed fire to be a distinct though yet inactive menstruum, the agency

of pressure and friction might have given motion to a more subtle interspersed element, and have communicated it to a naturally inert and folid mass immersed therein; but without fuch intervention we cannot conceive pressure to have any other effect but that of consolidating. We have seen that this author imagines the earth and other planets to be portions of this liquid fiery mass, which, whilst their parent sun continues in full vigour of fusion, have darkened and cooled, and are still cooling by degrees. The centre of our globe is still burning, and he asserts that the greatest part of the heat yet experienced on its surface proceeds from thence, and not, as was generally supposed, from the fun. Adopting the calculations of Mr. de Mairan, he determines this heat to be at present 31 times greater than that communicated by the sun; but as the centre cools it will gradually diminish, till at length the whole surface of the earth will become frozen and incapable of preserving animal or vegetable life. Mr. de Mairan's calculations are founded on a scale of degrees between extreme cold and extreme heat, applied to the unvaried temperature of the caves of the observatory at Paris, much greater than that of the air in times of frost. The heat of their atmosphere is constantly at 10 degrees of de


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