Pascal, then only twenty-four years of age, propos ed to write a treatise on the subject of those inquiries ; but thought proper, in the meantime, to publish a abort abstract of it, which appeared in 1647, and in volved him in a wretched controversy. Father Noel, rector of the Jesuits' College at Paris, keenly' attacked it, armed with all the miserable sophisms of the schools, and the absurd dogmas of the Romish church. He contended, that the space above the mercurial column was corporeal, because it was vi sible and admitted light ; that a void being a mere non-entity, cannot have different degrees of magni tude ; that the separation produced in the experi ments was violent and unnatural ; and he presupposed that the atmosphere, like blood, containing a mixture of the several elements, the fire and the finer part of the air were detached from it, and violently forced through the pores of the glass, to occupy the desert ed space. To enforce these puerile arguments, the reverend Jesuit did not scruple to employ the poi soned weapon which his order has often wielded with deadly effect,—the hinting an oblique charge of heresy. This rude attack only roused Pascal, and disposed him boldly to throw off the fetters of inve terate opinion. He began to perceive that " abhor rence" cannot, in strict logic, be applied to nature, which is a mere personification, and incapable of pas sion ; and was inclined, by degrees, to adopt the clear disembarrassed explication of Torricelli, referring the suspension of the mercurial column to the pressure of the external atmosphere. In stating this conclu sion, he makes some remarks which would deserve the serious attention of philosophers in the present age. " When the weakness of men is unable to find out the true causes of phenomena, they are apt to employ their subtlety in substituting imaginary ones, which they express by specious names that fill the ear, without satisfying the judgment. It is thus that the sympathy and antipathy of natural bodies are as serted to be the efficient and unequivocal , causes of several effects, as if inanimate substances were really capable of sympathy and antipathy. The same thing may be said of the antiperistasis, and various other chimerical causes, which afford only a vain relief to the avidity of men to know hidden truths, and which, far from discovering them, only serve to conceal the ignorance of those who invent such explications, and nourish it in their followers." These remarks, equally and profound, are the more striking, since rd Bacon, while he proposed to reform and new model the whole structure of human learning, yet complied with the taste of his age in retaining much of the jargon and barbarous distinctions of the schools.
But Pascal did not rest satisfied with mere reason ing, however strictly conducted ; and he soon devised an experiment which should palpably mark, under different circumstances, the varying effects of atmo spheric pressure. It occurred to him, that, if the mercury in the Torricellian tube were really support ed by the counterpoising weight of the atmosphere, it would be affected by the mass of superincumbent fluid, and must therefore partially subside in the higher elevations. He was impatient to have his con jecture tried in a favourable situation, and, in Novem ber 1647, he wrote a letter communicating those views to his brother-in-law, Perier, who filled an of fice of considerable trust in the province, and com monly resided at Clermont in Auvergne, in the im mediate vicinity of the Puy de Dome, a lofty coni.
cal mountain, which rose, according to estimation, 'above the altitude of 500 toises. Various avocations, however, prevented that intelligent person from com plying with his instructions, till the following year.
Early in the morning of the 19th of September 1648, a few curious friends joined him in the garden of a monastery, situate near the lowest part of the city of Clermont, where he had brought a quantity of mer cury, and two glass tubes hermetically sealed at the top. These he filled and inverted, as usual, and found the mercury to stand in both at the same i height, namely, 26 inches and Spines, or 28 Eng lish inches. Leaving one of the tubes behind, in the custody of the subprior, he proceeded with the other to the summit of the mountain, and repeated the ex periment, when his party were surprised and delighted to see the mercury sink more than three inches under the former mark, and remain suspended at the height of 23 inches and 2 lines, or 24.7 English inches. In his descent from the mountain, he observed, at two se veral stations, that the mercury succ,essively rose ; and, on his return to the monastery, he found it stood exact ly at the same point as at first. Encouraged by the suc cess of this memorable experiment, Perier repeated it on the highest tower of Clermont, and noted a difference of two lines at an elevation of 20 toises. Pascal, on his part, as soon as the intelligence reached him at Paris, where he then chanced to be, made similar observa tions on the top of a high house, and in the belfry of the church of St Jacques des Boucheries, near the border of the Seine ; and so much was he satisfied with the results, that he proposed already the appli cation of the barometer for measuring the relative height of distant places on the surface of the globe.
The investigation of the existence and effects of atmospheric pressure was now completed, and it threw a sudden blaze over the whole contexture of physical science. The fame of the experiments per formed in Italy and in France, quickly spread over Europe. Yet such is the force of habit and early prejudice, that, after the first moments of surprise and confusion, few of the learned at this period had the courage to open their eyes to the light which had so unexpectedly burst upon them; but, secretly che rishing their inveterate notions, they sought to com fort themselves, by starting a variety Of captious ob jections. Father Mersenne, though a man of some abilities, conceived that suction was occasioned by certain hooked particles dispersed through the atmo sphere, which laid hold of any fluid in contact with them, and drew it towards the general mass. Father Linus, plunging still deeper in mysticism and ab surdity, gravely proposed the funicular hypothesis, which attributes the suspension of the mercurial co lumn to the agency of certain small invisible threads. But others of the clergy attacked Pascal with en venomed bitterness. The Jesuits of the college of Montserrand scrupled not, in their public theses, to pervert his expressions, and even contest the origi nality of his experiments. The philosopher was just ly incensed at their base conduct; and those repeat ed provocations served, no doubt, to give a keener edge to his wit, when he afterwards directed it with such overwhelming energy against that insidious and formidable order of priesthood. He composed in 1653, though they were not published till after his death, two short treatises, On the Equilibrium of Liquors, and On the Weight of the Mass of Air, remarkable for their neatness, perspicuity, and lucid order. The laws of the equilibrium of fluids are there beautifully deduced from a single principle, which suggests a variety of original views and admirable remarks. In those tracts, he likewise gives a description of the Hydraulic Press, a most useful and powerful ma chine, which has lately been revived in this country, and considered as a new invention.