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sides outwards, are very pleasant 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:
"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; indeed of all our Senses. During that state
of collapse which it is just now the fashion to call "a Bilious Attack"
or a Nervous 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 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
Process, for which the Phrase of Fashion now is when you are Nervous or Bilious - the Eyelids are often affected with " Ophthalmia Tarsi," i.e. a slight Inflammation and an increased secretion of the glands about the Eye-lidswhich (in plain English) become gummed, and when the Eyes are first opened in the Morning, the Eye-lids feel stiff and the Eyes irritable.
The Eye-lids, are much oftener disordered than The Eyes;-perhaps three-fourths of what common people commonly call "Bad Eyes" are merely disease of The Eye-lids.
I have not space in my little Volume to descant on One of the 118 Principal Diseases of the Eye enumerated in the Work of the elaborately minute St. Yves, but having had Ocular demonstration of the efficacy and innocence of the following OINTMENT* FOR THE EYE-LIDS I here set it down.
One part of Citrine Ointment,
Three of fresh Lard
mix them thoroughly to
gether with an Ivory knife.
* "Whenever I am informed that the edges of the Eyelids have a disposition, be it ever so slight, to adhere to
The Eye-lids are to be anointed with a very little of this Ointment immediately before going
The Eye-lids should be washed in lukewarm water as soon as you rise in the morning — and every particle adhering to them, completely, but very gently and carefully removed — which is easiest done by soaking the Eye-lids by the repeated application of a soft cloth dipped into warm water till whatever sticks to them is loosened, then you may proceed cautiously to clean them.
each other after they have been long in contact, as during the time of sleep, and when this is accompanied with an uncomfortable sense of weight in the lids on the approach of night, in consequence whereof the patient involuntarily shuts them without being drowsy, and without any particular stimulus being applied to the Eye to give it pain, I always suspect that the secretion of the ciliary glands is in a diseased state; and in many such cases I have found the success attending the use of the Unguentum Hydrargyri Nitrati, recommended for the cure of this disorder, quite as effectual as in those other instances, where the excoriation and redness of the Eye-lids have been visible on the slightest inspection.” — Mr. WARE'S Chirurgical Obs. Vol. I. p. 116.
PRECEPTS FOR IMPROVING AND PRESERVING THE SIGHT.
THE Sensibility of the organ of Sight, is in proportion to the expansion of the Pupil* of the Eye, whose mean diameter is commonly calculated at about one 10th of an inch - but varies in magnitude, from One to at least Two tenths, according to the brightness of the object which is presented to it. See DR. HERSCHELL'S Paper in the Appendix.
When the Light is too strong, or the object too bright, the Pupil closes in order to inter
* In the 91st vol. of the Phil. Trans. page 86, in Dr. T. Young's paper on the Mechanism of the Eye-the Dr. has given in Plate v. Fig. 19, a drawing of the front view of his left Eye; "when the Pupil is contracted," the diameter of it is rather more than a tenth of an inch: and in Fig. 20, "The same view when the Pupil is dilated;" the latter measures almost two tenths and a half. See Copies of these Figures in Plate fronting the Title, Nos. 2 and 3, - in the openings of the Spectacle frame in the Frontispiece.