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else than the attainment or enjoyment of the last end. Now the last end is called happiness. If therefore the happiness of man is considered in its cause or object, in that way it is something uncreated; but if it is considered in essence, in that way happiness 's a created thing.

Happiness is said to be the sovereign good of man, because it is the attainment or enjoyment of the sovereign good.

So far as the happiness of man is something created, existing in the man himself, we must say that the happiness of man is an act. For happiness is the last perfection of man. But everything is perfect so far as it is in act; for potentiality without actuality is imperfect. Happiness therefore must consist in the last and crowning act of man. But it is manifest that activity is the last and crowning act of an active being; whence also it is called by the philosopher " the second act." And hence it is that each thing is said to be for the sake of its activity. It needs must be therefore that the happiness of man is a certain activity.

Life has two meanings. One way it means the very being of the living, and in that way happiness is not life; for of God alone can it be said that his own being is his happiness. In another way life is taken to mean the activity on the part of the living thing by which activity the principle of life is reduced to act. Thus we speak of an active or contemplative life, or of a life of pleasure; and in this way the last end is called life everlasting, as is clear from the text: "This is life everlasting, that they know thee, the only true God."

By the definition of Boëtius, that happiness is "a state made perfect by the aggregate sum of all things good," nothing else is meant than that the happy man is in a state of perfect good. But Aristotle has expressed the proper essence of happiness, showing by what it is that man is constituted in such a state, namely, by a certain activity.

Action is twofold. There is one variety that proceeds from the agent to exterior matter, as the action of cutting and burning, and such an activity cannot be happiness, for such activity is not an act and perfection of the agent, but rather of the patient. There is another action immanent, or remaining in the agent himself, as feeling, understanding, and willing. Such action is a perfection and act of the agent, and an activity of this sort may possibly be happiness.

Since happiness means some manner of final perfection, happiness must have different meanings according to the different grades of perfection that there are attainable by different beings capable of happiness. In God is happiness by essence, because his very being is his activity, because he does not enjoy any other thing than himself. In the angels final perfection is by way of a certain activity, whereby they are united to the uncreated good; and this activity is in them one and everlasting. In men, in the state of the present life, final perfection is by way of an activity whereby they are united to God. But this activity cannot be everlasting or continuous, and by consequence it is not one, because an act is multiplied by interruption; and, therefore, in this state of the present life, perfect happiness is not to be had by man. Hence the philosopher, placing the happiness of man in this life, says that it is imperfect, and after much discussion he comes to this conclusion: "We call them happy, so far as happiness can be predicated of men." But we have a promise from God of perfect happiness, when we shall be "like the angels in Heaven." As regards this perfect happiness, the objection drops, because in this state of happiness the mind of man is united to God by one continuous and everlasting activity. But in the present life, so far as we fall short of the unity and continuity of such an activity, so much do we lose of the perfection of happiness. There is, however, granted us a certain participation in happiness, and the more continuous and undivided the activity can be the more will it come up to the idea of happiness. And therefore in the active life, which is busied with many things, there is less of the essence of happiness than in the contemplative life, which is busy with the one occupation of the contemplation of truth.

From the third question of the "Ethics."

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RAGO, one of the founders of nineteenth-century science, was born near Perpignan, France, February 26th, 1786. His dis

coveries in magnetism and optics combined with his work as an astronomer to make him one of the most famous men of his day, and he increased his celebrity by his uncompromising republicanism. As a member of the French Chamber of Deputies in 1830, he was one of the leaders of the most advanced section of the Republican party. In 1848, after the fall of Louis Philippe, he became Minister of War and Marine, using his influence in the ministry to secure the abolition of slavery in the French colonies and of flogging in the army and navy. After the coup d'état he refused allegiance to Louis Napoleon, and offered his resignation from a scientific board of which he was a member. With a good taste he could show on occasion, Louis refused to accept it, and when Arago died, October 2d, 1853, decreed him a funeral with the highest possible honors. sides his numerous scientific works, Arago wrote a volume of studies of the lives of scientific men, which has become a part of popular literature in English as well as in French.

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THE CENTRAL FIRES OF THE EARTH

N ALL places of the earth, as soon as we descend to a certain depth, the thermometer no longer experiences either diurnal or annual variation. It marks the same degree, and the same fraction of a degree, from day to day, and from year to year. Such is the fact: what says theory?

Let us suppose, for a moment, that the earth has constantly received all its heat from the sun. Descend into its mass to a sufficient depth, and you will find, with Fourier, by the aid of calculation, a constant temperature for each day of the year. You will recognize further, that this solar temperature of the inferior strata varies from one climate to another; that in each country, finally, it ought to be always the same, so long as we do not descend to depths which are too great relatively to the earth's radius.

Well, the phenomena of nature stand in manifest contradiction to this result. The observations made in a multitude of mines, observations of the temperature of hot springs coming from different depths, have all given an increase of one degree of the centigrade for every twenty or thirty metres of depth. Thus, there was some inaccuracy in the hypothesis which we were discussing upon the footsteps of our colleague. It is not true that the temperature of the terrestrial strata may be attributed solely to the action of the solar rays.

This being established, the increase of heat which is observed in all climates when we penetrate into the interior of the globe is the manifest indication of an intrinsic heat. The earth, as Descartes and Leibnitz maintained it to be, but without being able to support their assertions by any demonstrative reasoning, thanks to a combination of the observations of physical inquirers with the analytical calculations of Fourier,-is an incrusted sun, the high temperature of which may be boldly invoked every time that the explanation of ancient geological phenomena will require it.

After having established that there is in our earth an inherent heat, a heat the source of which is not the sun, and which, if we may judge of it by the rapid increase which observation indicates, ought to be already sufficiently intense at the depth of only seven or eight leagues to hold in fusion all known substances, there arises the question, What is its precise value at the surface of the earth; what weight are we to attach to it in the determination of terrestrial temperatures; what part does it play in the phenomena of life?

According to Mairan, Buffon, and Bailly, this part is immense. For France, they estimate the heat which escapes from the interior of the earth, at twenty-nine times in summer, and four hundred times in winter, the heat which comes to us from the sun. Thus, contrary to general opinion, the heat of the body which illuminates us would form only a very small part of that whose propitious influence we feel.

This idea was developed with ability and great eloquence in the "Memoirs of the Academy," in "Les Époques de la Nature » of Buffon, in the letters from Bailly to Voltaire upon the "Origin of the Sciences" and upon the "Atlantide." But the ingenious romance to which it has served as a base has vanished like a shadow before the torch of mathematical science.

FRANÇOIS JEAN DOMINIQUE ARAGO

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Fourier, having discovered that the excess of the aggregate temperature of the earth's surface above that which would result from the sole action of the solar rays has a determinate relation to the increase of temperature at different depths, succeeded in deducing from the experimental value of this increase a numerical determination of the excess in question. This excess is the thermometric effect which the solar heat produces at the surface; now, instead of the large numbers adopted by Mairan, Bailly, and Buffon, what has our colleague found? A thirtieth of a degree, not more.

The surface of the earth, which originally was perhaps incandescent, has cooled then, in the course of ages, so as hardly to preserve any sensible trace of its primitive heat. However, at great depths, the original heat is still enormous. Time will alter sensibly the internal temperature; but at the surface (and the phenomena of the surface can alone modify or compromise the existence of living beings), all the changes are almost accomplished. The frightful freezing of the earth, the epoch of which Buffon fixed at the instant when the central heat would be totally dissipated, is then a pure dream. At the surface the earth is no longer impregnated except by the solar heat. So long as the sun shall continue to preserve the same brightness, mankind will find, from pole to pole, under each latitude, the climates which have permitted them to live and to establish their residence. These are great results. While recording them in the annals of science, historians will not neglect to draw attention to this singular peculiarity: that the geometer, to whom we owe the first certain demonstration of the existence of a heat independent of a solar influence in the interior of the earth, has annihilated the immense part which this primitive heat was made to play in the explanation of the phenomena of terrestrial temperature.

Besides divesting the theory of climates of an error which occupied a prominent place in science, supported as it was by the imposing authority of Mairan, of Bailly, and of Buffon, Fourier is entitled to the merit of a still more striking achievement: he has introduced into this theory a consideration which hitherto had been totally neglected; he has pointed out the influence exercised by the temperature of the celestial regions, amid which the hearth describes its immense orbit around the sun.

When we perceive, even under the equator, certain mountains covered with eternal snow, upon observing the rapid dimi

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