Algebra,' a work that has been translated into every language of Europe, was dictated by him when blind to an amanuensis, who was only a tailor's apprentice; but who, though altogether unacquainted with algebra when he began his task, is said to have acquired a complete knowledge of that science in the course of merely taking down what Euler spoke, with such admirable clearness and simplicity is the work composed. His Algebra was followed by several other inost ingenious and elaborate works, among which particularly deserve to be mentioned his New Theory of the Moon's Motions,' and the tables by which it was accompanied, the computation of which, by a person in Euler's situation, not only deprived of sight, but harassed by other misfortunes, (for while he was engaged on this work, his house was burned to the ground by a fire, from which he narrowly escaped with his life,) cannot but be regarded as one of the most wonderful triumphs ever achieved by the energy of mind over the opposition of circumstances. But Euler affords us in every way the most remarkable example on record of activity in scientific labours. The mere catalogue which has been published of his works extends to fifty printed pages. It may be asserted, without exaggeration," says Lacroix* "that he composed more than one half of the mathematical memoirs contained in the forty-six quarto volumes which the academy of Petersburg published from 1727 to 1783; and he left at his death about a hundred memoirs ready for the press, which the same academy inserts successively in the volumes it still continues to give to the world. In addition to this immense mass of productions, he composed various separate works, extremely important in respect of the subjects of which they treat, and many of them of considerable magnitude.

Biographie Universelle

He

likewise greatly enriched the collections of the academy of Berlin, during the twenty-five years which he passed in that city. He presented several memoirs to the Academy of Sciences of Paris, the prizes offered by which he ten times succeeded in carrying or dividing; nor did he disdain to contribute to the transactions of less illustrious associations of the learned. In fine, it requires the incontrovertible evidence of facts to convince us that so many labours can all have been performed by one man, who passed the last seventeen years of his life in a state of blindness." As a proof that even this statement rather underrates than exaggerates the amazing industry and fertility of Euler, we may just add, that, in the list of his works already referred to, there are enumerated, of separate publications alone, twenty-nine volumes quarto, and two octavo, in Latin; volume quarto, and six octavo, in German; and five volumes octavo, in French.

one

We may mention still another, though certainly a very inferior name, that of the late Dr. HENRY MOYES. Moyes was born at Kirkaldy, in Fifeshire, and lost his sight by small-pox before he was three years old, so that he scarcely retained in after-life any recollection of having ever seen. Yet he used to say, that he remembered having once observed a water-mill in motion; and it is characteristic of the tendencies of his mind, that even at that early age his attention was attracted by the circumstance of the water flowing in one direction, while the wheel (having been what is called an undershot wheel) turned round in the opposite, a mystery on which he reflected for some time before he could comprehend it. Blind as he was, he distinguished himself when a boy, by his proficiency in all the usual branches of a literary education. But "mechanical exercises," says Mr. Bew, who has given a short account of him

in the first volume of the Memoirs of the Literary and Philosophical Society of Manchester,' “ were the favourite employments of his infant years. At a very early age he made himself acquainted with the use of edged tools so perfectly, that, notwithstanding his entire blindness, he was able to make little windmills; and he even constructed a loom with his own hands, which still shew the cicatrices of wounds he received in the execution of these juvenile exploits." Besides a knowledge of the ancient languages, and of music, he is stated by Mr. Bew, who became acquainted with him about the year 1782, to have made himself extensively conversant with Algebra and Geometry, and with Chemistry, Mechanics, Optics, Astronomy, and the other departments of Natural Science. At this time he was engaged in delivering lectures on Chemistry and Natural Philosophy in the different large towns throughout the country. He used to perform all his experiments, we are told, with his own hands, and with extraordinary neatness. Moyes possessed all that extreme delicacy in the senses of touch and hearing for which the blind have usually been remarkable. We have been told, that having been one day accosted in the street by a young friend whom he had not met with for a good many years, his instant remark, on hearing his voice, was, how much taller you have grown since we last met! When first brought into a company, his custom was to remain silent for a short time, until by the sound of the different voices he had made himself acquainted with the size of the room, and the number of persons in it. He was then quite at his ease, readily distinguished one speaker from another, and shone greatly himself by his powers of conversation. Although at that time not in affluent circumstances, and having indeed nothing to depend upon except the very precarious

occupation to which he had betaken hi.nself, he was remarkable for his cheerfulness and buoyant spirits. He contrived for himself a system of palpable arithmetic, on a different principle from that of Saunderson, and possessing the advantage in point of neatness and simplicity. An explanation of it may be found in a letter from himself, inserted in the 'Encyclopædia Britannica' under the article Blind. Dr. Moyes, who must have been a person of extraordinary mental endowments, and who affords us certainly, next to Saunderson, the most striking example on record of attainments in the Mathematics, made without any assistance from the eye, received his degree from a college in America, in which country he lectured for some years.

He

eventually made in this way a good deal of money; and some time before his death had retired to the town of Pittenweem, not far from his native place, where his society was much courted. His lectures are said to have been well delivered, and his explanations were eminently perspicuous. It has been reported that he could distinguish colours by the touch; but as this circumstance is not mentioned in his friend Dr. Blacklock's article just referred to, we may fairly assume that he did not himself pretend to the possession of any such power.

CHAPTER XVIII.

Difficulties occasioned by Blindness conquered.

Homer: Milton; Salinas; Stanley; Metcalf; Henry the Minstrel; Scapinelli; Black lock; Anna Williams; Huber.

But,

MATHEMATICAL investigation is, strictly speaking, merely a mental exercise, and it is certainly conceivable that every theorem man has yet demonstrated in abstract science might have been discovered by him without the aid of his external senses. on the other hand, every operation of mind is so greatly facilitated by the employment of sensible symbols, and especially the processes of acquiring, apprehending, and recollecting knowledge, as well as of pursuing long and intricate calculations or deductions, receive such important assistance from those lines, figures, letters, and other marks which may be made to present the record of every thought faithfully to the eye, that we are justified in quoting any remarkable case of progress, even in abstract science, attained without the aid of this invaluable organ, as a noble example of what perseverance may accomplish in the face of the most formidable difficulties. It is much even for the mind to rise superior to so crushing a calamity as the loss of sight, and to maintain or recover its spirit of exertion under a deprivation which may be said to take from it for ever that which nature has appointed to be at once the chief helpmate and best sweetener of its labours. It would seem almost as if life could scarcely continue desirable to him whose hourly