too before very long. Constantin Huygens, secretary to the Prince of Orange, a courtier and one of the beaux esprits of the day, was amongst the former; and his family, of whom the great mathematician of later days was one, were included in the number of the philosopher's acquaintance. Their country-house near the Hague must have been an agreeable place of resort. In Amsterdam, also, well supplied with butchers' shops, Descartes sometimes lived in order to find material for his anatomical studies, and at Endegeest, near Leyden, he had a charming abode, a portion of which is still to be seen in the midst of an asylum for the insane. It was in scenes like these that Descartes composed and published his Method' and 'Meditations.' But publication, both scientific and philosophical, was delayed owing to a matter which was agitating Europe.

On June 23, 1633, Galileo was condemned by the Inquisition for his 'Dialogue on the two greatest Systems of the World'-those of Ptolemy and Copernicus. The time-honoured doctrine of an immovable earth, in the centre of the universe, round which the firmament turned, was threatened, and the Holy Office felt the time had come to interfere. Now the movements of the earth had formed an integral part of Descartes' theory of physics, and he found himself to his alarm liable to a similar condemnation. No personal injury threatened him in the land he had chosen as the home of his exile; why should he have been so disturbed? M. Adam is clear that it was the ultimate triumph of his ideas that really troubled him, rather than any personal fears. He wanted them to gain entrance, not only to the enlightened spirits, but also to the universities and schools. He hoped to have on his side not only his old friends the Jesuit fathers, but the professors of Louvain and even Douai. What object was there, then, in publishing his 'World,' which would certainly set all these influential persons by the ears? The suppression of this, his first important work (it appeared finally in another form), was not the greatest harm that was done by Descartes' fears. As M. Adam justly remarks, through the sentence of the Inquisition we are deprived of the true Descartes. The Church brought about a moral intimidation which really retarded the progress of science and philosophy for the

time. Science was compelled to disown her findings. The philosophic figures of the century, the new philosophy that was to carry its influence right down to the present day, suffered a check. In point of fact, Descartes found means of presenting his ideas in a modified form, so that he should not have reason to feel anxious about the results that they might bring about. He carefully explained that his system of the heavens resembled that of Tycho-Brahé, rather than that of Copernicus, thereby effecting a sort of half-hearted compromise. But so far as his theories of the world were concerned, they never again displayed the absolute spontaneity that they would otherwise have possessed.

His first actual publication took the form of Essays on Dioptric [which M. Adam thinks might have been called the Telescope], Meteors and Geometry,' with the ever-famous 'Discourse on Method,' an autobiography as well as a discourse, as their preface. This appeared in 1637, and the following years were taken up with the usual polemics that in those days followed the publication of a notable book on controversial subjects. It was three years later that the 'Meditations' were ready for the printer, and it was written in Latin, whereas the first work had been in French, so that anyone-' even women -might read and understand it. The Meditations' had been sent round the learned of the day for purposes of criticism, and amongst those who responded were Arnauld, of Port Royal fame, and the English Hobbes. With the latter Descartes, of course, had little in common, but Arnauld-the great Arnauld-was an opponent for whom he had an almost exaggerated respect; and it was with him that he discussed that never-failing topic, the true meaning of the Eucharist. In 1644 there followed Descartes' other great work, the 'Principles,' though meanwhile he had been engaged in interminable disputes with theologians and philosophers. This book is a complete scientific statement of how the world and all its manifestations in nature were capable of explanation by methods which were at least rational and possible, however strange they may seem to us. Descartes' idea always was to have a theory of how the operations of nature might be rationally carried on, rather than to trust to the vague surmises and traditional

beliefs of his predecessors; and this was a real advance in the scientific standpoint.

But while immersed in his profounder studies an influence had come into Descartes' life of a quite new kind. Love, as we have said, did not play any great part in his existence, but with Platonic friendships it was otherwise. The strange thing about these friendships was that both of them were with women of royal blood; and we cannot help wondering whether his extraordinary reverence for royalty had not something to do with the exuberance of his feelings. His doctrines of Divine Right are not such as we often hear in these days; he believes that 'the means taken by princes to establish themselves are nearly always righteous if they believe them so to be,' and 'God gives the right to those to whom he gives the strength.' This was written to Princess Elizabeth, eldest daughter of Elizabeth of Bohemia, the Queen of Hearts, and granddaughter of our King James I, and to Frederick V, Elector Palatine, who was crowned at Prague and lost his kingdom in the following year by that battle at which Descartes himself was very probably present. The family took refuge at the Hague, where they kept up a little exile court. After her husband's death, the Electress continued to make the Hague her home and that of her ten children, who must indeed have been a lively crew. Amongst them were Rupert of the Civil Wars, Maurice, and Sophia, mother of King George I of England. Elizabeth was the eldest of the daughters, and besides being remarkably gifted intellectually by nature, she was well instructed by her teachers in modern languages, Latin and mathematics. Although a strong Protestant in religion, she was strongly attracted by the distinguished philosopher whom she made her friend. In her younger days she was far from a recluse, but as time went on and trouble, family and other, came to her, she turned for consolation to the philosophy she had learned to care for from her friend and master. It was long after his death that she found peace in the Abbey of Hervorden, where, as Abbess, she was able to offer refuge to her old friend Anna Maria Schurmann, another learned lady of the day, and where she also entertained William Penn the Quaker. She died there, finding satisfaction in the somewhat mystical views of Labadie, though at the

same time she was always faithful to the teaching of Descartes.

Elizabeth was a remarkable woman, and her letters show true appreciation of the problems she discussed with Descartes when her correspondence was not occupied with her own woes, physical and mental. There was a family scandal at the Hague, as a result of which a Frenchman was killed by one of Elizabeth's brothers in circumstances not yet cleared up. But the issue was that Elizabeth, whether personally involved or not, departed from Holland and never returned-a sad distress to her. The subsequent execution of her uncle, Charles I of England, was one of the keen trials which she, like the rest of this suffering but courageous family, had to meet. And besides, there were frequent difficulties of other sorts, in all of which Descartes was ready with his sympathy. He always enjoyed prescribing for his friends, and he had ample opportunities of doing this in the young princess's case, for her health was often far from good, and he had the consolation that few lay physicians enjoy, of knowing that his advice would certainly be followed. A mind diseased appealed to him as strongly as a body, and 'The Passions of the Soul,' one of his later works, was written in order to meet the objections to his philosophy made by his royal friend. The complete correspondence between the two is to be found in the edition which is before us; some day it may be, one may hope, published in a separate and more accessible form.

Descartes' interest in science was, as we know, as keen as his interest in speculative philosophy, and at this time there was a scientific problem which concerned him deeply. The great and world-famed experiment on the decrease of barometric pressure with altitude was made on September 19, 1648, on the Puy-de-Dôme mountain in Auvergne. The nature and amount of atmospheric pressure was first discussed and measured by Torricelli, whose account of the subject was conveyed from Italy to France by Mersenne, who made it known to friends in Paris. Mersenne, however, could not satisfactorily repeat the experiment, despite many efforts in which Chanut helped him. Petit succeeded in doing so with mercury, and Pascal carried out further experiments with other

liquids and long tubes expressly made for the purpose. It was Descartes, however, who suggested that the experiment should be made of measuring the height of the column of mercury at the foot and at the top of a mountain respectively, since he expected that the pressure of air on the mercury would decrease as the mountain was ascended, and hence the mercury in the tube would fall. When he suggested this to Pascal, Pascal got his brother-in-law to carry out what became the famous experiment. Pascal published an account of it, but Descartes did not hear of the publication for several months subsequently, and was somewhat hurt at receiving no recognition of his suggestion. The whole story, with Jacqueline Pascal's account of Descartes' visit to her brother, then a young man of twenty-five living in Paris, is one of the most interesting of the many romances of scientific discovery. Descartes' part in it has been overlooked (just as was Mersenne's until recent times), but that he is entitled to a considerable amount of credit in the discovery of the behaviour of the barometer-credit which never was accorded to him-is indubitable if we are to accept M. Adam's account; and he has studied the whole question most carefully in connexion with the original documents, some of which were until recently overlooked.

To return to the story of Descartes' life. A visit to Paris during the troubles of the Fronde, when he found himself in the position of a 'guest arriving when the kitchen was in disorder and the saucepans upset,' gave Descartes little pleasure, though we cannot but feel a wish to have heard more of a dinner party given by the Marquis of Newcastle to Hobbes, Descartes and Gassendi, a very remarkable trio of guests. Back in his hermitage' at Egmond he set himself to work at his various experiments and also to complete the Passions,' the lastpublished of his books. But we have no reason, in spite of his solitary life, to look on Descartes as a pedant; he was also an honnête homme in the 17th-century sense of that phrase.

Now comes the last stage in this remarkable life story. Queen Christina of Sweden desired to make for herself and her country a reputation, but of another kind from