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 Eye

lids 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

to rest.

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.

CHAPTER XII.

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 Frontis piece.

G

cept that excess of Light* which would otherwise offend the Eye :- when the Light is faint, the Pupil expands that a greater quantity of it may enter the Eye, and thus make a stronger impression upon it.

the

This contraction and dilation of the Pupil, you may easily discern by holding a lookingglass before your Eye at a window and turning gradually round from the window continually looking at your Eye in the looking-glass lowest small speculum of a Gregorian Telescope, as it magnifies a little, will shew you this still plainer:-and it may be easily and perfectly observed by attentively watching the Eye of another, during such a change of posi

*"95. The sensibility of the Eye, and its power to discern objects without inconvenience by different quantities of Light is vastly extensive. For instance, the disproportion in the quantities of Light cast upon the horizon by the Sun, and Moon, at equal altitudes, I find is no less than 90,000 to 1, when the Moon is full.

"Day-light is to Moon-light as the surface of an Hemisphere whose centre is at the Eye, to the part of that surface which appears to be possessed by the enlightened part of the Moon: so that the whole Heavens covered with Moons would only make Day-light."-Dr. SMITH's Optics, 4to. 1738, p. 29.

tion-it is most visible in a fine full bright blue Eye.

The fact that the sensibility of the Sight* is in proportion to the diameter of the Pupil, is strongly illustrated by the following circumstance. "What can be the reason," a very intelligent and accurately observing Artist said to me, who was sitting by the side of his window," that when I look at that portrait opposite to me, it looks Warm with my left Eye, and Cold with my Right; i. e. with my Left Eye, which is from the window, it appears

* We can never be certain that an Object does now appear to us of the same precise Colour of which it appeared last Day or last Week: neither can our being insensible to any change ever prove to us that the Colour is the same. Not only different Persons may have different sensations of Colours, proceeding from the different dispositions of their optic nerves and Retinæ, or from the different tinctures wherewith their Eyes are tinged, but also the same person may, from the same causes, see the same Object, differently coloured at different times without being sensible of it; and experiments are not wanting, whereby it appears, that the same object was seen of different colours, according as it was viewed with the right or left Eye."-Dr. PORTERFIELD on the Eye, 8vo. 1759, Vol. I. p.128.