quote, with great readiness, the books, of which he had acquired a knowledge only from having heard them read by others.*

To these instances, we may add that of the COUNT DE PAGAN, who was born in the beginning of the seventeenth century, and has been accounted the father of the modern science of fortification. Having entered the army, at the early age of twelve, he lost his left eye, before he was seventeen, at the siege of Montauban. He still, however, pursued his profession, with unabated ardor, and distinguished himself, by many acts of brilliant courage. At last, when about to be sent into Portugal with the rank of field-marshal, he was seized with an illness, which deprived him of his remaining eye. He was yet only in his thirty-eighth year, and he determined that the misfortunes, he had already sustained, in the service of his country, should not prevent him from recommencing his public career, in a new character. He had always been attached to mathematics, and he now devoted himself, assiduously, to the prosecution of his favorite study, with a view, principally, to the improvement of the science of fortification, for which his great experience in the field, particularly fitted him. During the twenty years after this, which he passed in a state of total blindness, he gave a variety of publications to the world; among which, may be mentioned, besides his wellknown and largest work, on Fortification, his Geometrical Theorems,' and his Astronomical Tables.' He is also the author of a rare book called 'An Histo

(

* It was the example of Nicaise de Vourde, which excited another blind individual, Dr. Nicholas Bacon, to pursue the study of the law. Dr. Blacklock, in the article on the Blind, which he wrote for the Encyclopædia Britannica, informs us, that he had corresponded by letter with this gentleman, who resided in the Netherlands, but was, he says, of the same family with the Lord Chancellor Bacon. He lost his sight, when only nine years old, by a wound from an arrow; but, having recovered his health, he determined to continue his studies as before, until, as well as Nicaise, he should obtain his degree of Doctor of Laws. Accordingly, having finished his education at school, he proceeded to college, where, having greatly distinguished himself, he in due time attained the title of which he was so ambitious, and became, eventually, one of the most eminent advocates in the council of Brabant.

I.

20

P. K.

rical and Geographical Acccunt of the River of the Amazons,' which is remarkable, as containing a chart, asserted to have been made by himself, after he was blind. It is said not to be very correct, although a wonderful production for such an artist.

The distinguished mathematician, EULER, was struck with blindness, in his fifty-ninth year, his sight having fallen a sacrifice to his indefatigable application. He had literally written and calculated himself blind. Yet, after this misfortune, he continued to calculate, and to dictate books, at least, if not to write them, as actively as ever. HisLlements of 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 spcke; with such admirable clearness and simplicity is the work composed. His Algebra was followed by several other most 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 circum

stances.

But Euler affords us, in every way, the most remarkable example, on record, of activity in scientific labors. 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

* Eiographie Universelle.

the Academy of Petersburgh 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 thein of considerable magnitude. 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 labors 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; one volume, quarto, and six, octavo, in German; and five volumes, octavo, in French.

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 smallpox, before he was three years old, so that he scarcely retained, in afterlife, any recollection of having ever seen. Yet he used to say, that he remembered having once observed a watermill 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 favorite 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 show 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 himself, he was remarkable for his cheerfulness and buoyant spirits. He contrived, for himself, a system of palpable arithmetic, on a different principle

DIFFICULTIES OCCASIONED BY BLINDNESS. 233

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 extraor dinary mental endowments, and who aflords 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 perspicucus. It has been reported, that he could distinguish colors by the touch; but, as this circumstance is not mentioned in his friend. Dr. Blacklock's article, just referred to, we may fairly as sume that he did not himself pretend to the possession of any such power.

CHAPTER XV.

Difficulties occasioned by Blindness, conquered:— Homer; Milton; Salinas; Stanley; Metcalf; Henry the Minstrel; Scapinelli; Blacklock; Anna Williams; Huber. NOTE.

MATHEMATICAL investigation is, strictly speaking, merely a mental exercise, and it is certainly conceivable, that every theorem, man has yet demonstrated, in alstract science, might have been discovered by him, without the aid of his external senses. But, on the other hand, every operation of mind is so greatly facilitated, by the employment of sensible symbols, and, especially, the