makers of fine Pieces of Workmanship, such as Clocks and Watches, that many of the Workmen are almost Blind before they arrive at Old Age. I know a Jewish Woman in this City that had a peculiar way of stringing of Pearls, so as to cover their blemishes if there were any, and by that means got a deal of money; but when she came to be forty years of age, finding no manner of relief from Spectacles, she was forced to leave off the Business. I remember likewise to have heard several Printers complain, that they have given a considerable shock to their Eye-sight by composing small types.

"In earnest, I do not see how we can afford any Relief to the Workmen we now treat of; for it is not easy to persuade them to leave a beneficial and lucrative trade; and Physic is unprovided with any Remedy that can restore the primitive Strength and Mobility of the Eyes, after the Disorder has become inveterate: for neither Purging, nor Bleeding, nor other Medicinal Means, can take place in this Case, in regard the Patients are otherwise Well and Brisk, and their Spirits being neither clouded nor incrassated, it would be improper to punish an

innocent and sound Head with the Commotions

of Medicines.

"However, I would advise such Workmen not only to use Spectacles, but to intermit from their Work now and then, and refresh their Eyes by Diversity of Objects. For we can't imagine How much the Mobility of the Membranes of the Eyes, and the native Fluidity of the Humours, is kept up by viewing divers Objects; some near at hand, some remote, some directly, others obliquely; and, in fine, all manner of ways: for by this Means the natural Disposition of the Eye is preserved, so that the Ball is sometimes contracted, and sometimes dilated; and the Crystalline Humour approaches more or less to the Pupilla, according as the remoteness or nearness of the Object requires. Without this Diversity of Action, the Eyes undergo the same Fate with the other parts, that, by being long detained in one position, grow stiff and unfit for Motion."-RAMMAZZINI on the Diseases of Tradesmen, chap. xxix. of the Eng. Trans. 8vo. 1705, p. 219.

WATCH-MAKERS, ENGRAVERS, and those who are in the habit of using Strong Magnifiers, would feel their Eyes much less fatigued, if

the objects they examine were always placed at once, and kept at the proper focus: this might be contrived very easily, by fixing the Magnifying-glass in the opening of a Spectacle frame, or on a stand, and making a mark where the object of examination is most distinct.

Nothing can be more detrimental to the organ of sight than the clumsy practice of holding a glass by squeezing the orbicularis muscle, this cannot be done without distorting, and distressing, and much injuring the mechanism of the Eye.

The less the Magnifying Power of the Glass, the less the Eye will be fatigued by it, the less distressing the position of the Body in working with it, and the larger and more uniformly distinct the field of view: and where a moderate Magnifying power is sufficient-instead of a single magnifier, I think it will be better, especially for Etching, and for examining the general Effect of Engraving, &c. to wear Spectacles of 9 inches focus with which I think that Artists might work longer than with only one Eye.

The Compound Magnifiers, which are composed of two plano-convexes with their plane

sides outwards, are very pleasant as they have a large and uniformly distinct field.I have not met with any body who was aware this construction of Eye-glass was invented so long ago as appears by the quotation I

here insert:

[ocr errors]

"Eustachio Divini hath made a Microscope with two plano-convex Glasses, which are so placed as to touch one another in the middle of their convex surface and hath this peculiar quality, that it shews the object flat and not crooked; and although it takes in much, yet magnifieth extraordinarily."-See Phil. Trans. for 1668, Vol. III. p. 842.

Concaves which make objects appear the size Artists wish to draw them, are very useful to Miniature Painters, who should have them of two or three different degrees of Concavity-so mounted on a stem that they may be used separately or altogether: thus they may see an object of 6 Feet in diameter reduced to exactly the size it is to be delineated, i. e. to any degree between 6 Inches in Diameter, and half an inch in Diameter.

The condition of our Corporeal Machinery, has great influence on that of our Eyes; — and indeed of all our Senses. During that state

[ocr errors]

or a Nervous

of collapse which it is just now the fashion to call " a Bilious Attack" Paroxysm"-just in proportion that we are out of Heart, -the Circulation is feeble and languid, and every sense performs its functions imperfectly. During such prostration of the Vital powers, it is not uncommon to hear people complain of NERVOUS DEAFNESS.-It is equally common for them to be afflicted in an equal degreee with NERVOUS DIMNESS OF SIGHT.

This occasional dulness of the Ears, is oftener observed, than the dimness of the Eyes; - because the former defect is obvious to others, the latter is confined very much to ourselves; and unless we happen to want to minutely examine some minimum visibile, which requires all the powers of the Sight to be in full force to be discernible, such a paroxysm of Ocular obtuseness often passes unnoticed, and is seldom strong enough to excite the attention of healthful persons, until they have passed their 40th year; who will then generally find, that it may be traced either to over-exertion of the Eyes, or to some Disorder of the Digestive Organs.

During derangements of the Restorative

« VorigeDoorgaan »