Green glass may be fixed in them, but it must be of a very light Colour.

Some more nice than wise folks, among other ridiculous refinements have recommended thin Green-Gauze or Crape, instead of Green Glass

-under the pretence, that while it moderates the Light, that it still admits the Air, and is, therefore, cooler to the Eyes.

All Coloured Glasses increase the labour of the Eyes, and soon bring them into such an irritable state as unfits them for all the ordinary purposes of Life: - there is scarcely an external or internal Sense, but may be brought by extreme indulgence, to such a degree of morbid delicacy and acuteness, as to render those organs which nature intended as sources of

which he took to gratify his revenge, and satiate the savage cruelty of his Temper, was accustomed to bring forth his miserable Captives from the deepest recesses of the darkest Dungeons, into white and well lighted Rooms, that he might blind them by the sudden transition from one extreme to the other.

"Actuated by principles equally barbarous, the Carthaginians cut off the Eye-lids of Regulus and then exposed him to the bright rays of the Sun - by which he was very soon blinded."-G. ADAMS on Vision, 8vo. 1789, p. 8.

gratification — the frequent sources of Disappointment and Pain.

The most proper material for Spectacle Glasses, is that which shews objects the nearest to their natural Colour.

Lastly—Whatever Glasses you use

take

care to "keep them perfectly clean:" this is as important, as the choice of the Figure or the Colour of them.

finding that

Every time you wipe your Spectacles you scratch them a little, and "many a little makes a mickle"-therefore, when you have done using them, put them away carefully in their case, to prevent other people abusing themas a Naughty Boy did his Grand Pa's Spectacles - who took the Glasses out and when the old Gentleman put them on he could not see, exclaimed, " Marcy me, I've lost my Sight!"-but thinking the impediment to Vision might be the dirtiness of the Glasses -took them off to wipe them-when not feeling them, he, still more frightened, cried out, "Why what's come now, why I've lost my Feeling too!"

CHAPTER XIII.

GLASSES FOR SHORT-SIGHTED PERSONS.

I HAVE met with several persons of 30 and 40 years of Age who had no notion that they were Near-sighted, until they accidentally looked through my Spectacles at a distant object; when they exclaimed with surprise, "Bless me, how clearly I see! I never saw any Glasses before, that I could see so well with as with my naked Eye, and therefore had no idea that any Glass could improve my sight."

"I can see to read a small print, as well as any body I believe, but I have sometimes suspected that I did not see any thing across the street, or at a Theatre, quite so plainly as I have heard other people say that they did; and I suppose that the Spectacles which I tried before were not suitable to my Sightand so I had no idea that any Glass could improve my Sight."

For such Eyes I have procured a No. 1, or No. 2, Concave and they have been delighted —and said, "Well, I see now that I have never

S

before discerned the distinct outline of any object which has been further than a few feet from me."

Being a Short-sighted mortal myself, I write this Chapter with confidence, from my own. experience of upwards of 31 years, and hope to be able to give some good advice to those who are unfortunately what is called Near-sighted· by briefly narrating "the History of my own Case of Spectacles."

I was about 15 years old, when I first discovered that I could not discern distant objects so distinctly as people who have common Eyes usually do.

Mr. WARE, whose paper on Shortsightedness I had not seen till after I had written this Chapter, has remarked, (see Appendix,) that Young People seldom find out that they are remarkably Short-sighted, until about the time that I did; which is true, and perhaps for this reason, that Young Folks seldom attend to any thing in earnest before they attain to that Age - when seeing, that I could not see what persons with common Eyes frequently pointed out to me as well deserving my attention, I paid a

visit to an Optician and purchased a Concave Eye-glass No. 2.

After using this some little time, I accidentally looked through a Concave No. 3, and finding my Sight much sharper with this, than with No. 2-had my Spectacles glassed with No. 3, which appeared to afford my Eye as much assistance as it could receive.

After using No. 3 for a few Months, I chanced to look through No. 4, and again found the same increase of Sharpness, &c. which I perceived before when I had been using No. 2 and first saw through No. 3- therefore concluded that I had not yet got Glasses sufficiently Concave, and accordingly procured No. 4: - however, this soon became no more stimulus to the Optic Nerve - than its predecessors Nos. 2 and 3 had been.

I then began to think that the Sight is subject to the same laws which govern the other parts of our System; i. e. an increased Stimulus by repetition soon loses its power to produce an increased effect therefore, I refused my Eye any further assistance than it received from Spectacles glassed with No. 2, which I have