INTRODUCTION.

GENERAL OBSERVATIONS ON SPECTACLES.

WITHOUT SPECTACLES all the other working tools, of most Artists, soon after their 40th year, would be almost useless.

At that precious period of Life, when Genius begins to wait upon Judgment,† the persevering Student would no longer be able to enjoy the fruits of the labours of his Predecessors, or to preserve the produce of his own for the benefit of Posterity.

"Were there no other use of Optics, than the invention of Spectacles for the help of defective Eyes, I should think the advantage which mankind receives thereby, inferior to no other benefit whatever, not absolutely requisite to support Life." - MOLYNEUX's Optics.

"The exact time when years have ripened the Judgment, without diminishing the Imagination, by good critics is held to be punctually at Forty."-See MARTIN SCRIBLERUS on the Dunciad, p. 55.

The accomplished Artist, almost as soon as he acquires his Art, would be incapable of pursuing it, the seeds of perfection which he has been industriously cultivating during the First period of Life, would very soon after cease to be productive, and, but for the Eyeinvigorating Art of the Optician, his latter days would be melancholy and forlorn.

It is hoped that by a little attention to the following pages, that All who can hear,* may be enabled to procure precisely such Glasses as are most proper for them.

Every body is in want of such Information, because Nobody has given it,—therefore, I have endeavoured to render it as easily attainable, as it is universally desirable, by communicating it in such plain terms that Every body may understand.

The choice of Spectacles is one of those acts which cannot be properly performed by proxy - the Sight cannot be perfectly suited, unless

"Every Eye negociate for itself."

It is presumed, that the majority of the purchasers of this Work, cannot See! till they have learned how by the instructions herein given.

This is so absolutely true, that not only One Person cannot choose for Another- but One Eye has often very little notion what Glass will be best even for its own Brother, so extremely does the Left Eye occasionally differ from the Right.

No faculty of man varies more in its nature, or is susceptible of so high a degree of Improvement and Refinement by Art, as the Sense of Sight. The highest degrees of its discriminating power are acquired slowly and imperceptibly.

From organic imperfection and neglect of cultivation,* many People pass through Life who (it may be said, comparatively,) never Seei. e. whose Eyes never have the faculty of accurately appreciating either Form - or Colour:to very few indeed is it given to perfectly perceive and portray both.

There cannot be a more evident proof of the

"Every person acquainted with Optics and the nature of vision, knows that what is generally comprehended under the term Seeing, is a complex operation; an art acquired by degrees, in which judgment and imagination are concerned together with simple perception." — CRISP on Vision, 8vo. 1796, p. 106.

general defect in people's Sight — than the general acceptance of capricious and unreasonable Fashions, which appear to be prevalent, in proportion that they are in direct opposition to all the principles of good taste, and which to a fine Eye, are frequently frightful, and absolutely painful to behold.

From the different modes of colouring of different Artists, I suppose that the Eyes of no two Painters feel exactly the same impression of colours, and objects, appear of different Colours accordingly as they are illuminated with different Lights.

"The Mole's dim curtain, and the Lynx's beam,"

POPE. do not differ more extremely than does the Sight of different persons- and of the same persons at different Ages.

The peculiar conformation of the Eyes, differs quite as much in different persons, as the construction of their Noses;-it is just as impossible to guess exactly what Spectacles will best suit the Sight of another Person, as it is to tell what Tunes are most delightful to or what Tastes are most delicious

his Ear,

to his Tongue.

Nothing can be more erroneous than the common notion, that there is an invariable Rule, that a certain form of Glass is calculated for a certain Age. No Rule has more exceptions: but this Vulgar Error has been productive of great and irremediable Injury to the Eyes of Thousands !

Hence, the grand desideratum, is to instruct people how to choose wisely for Themselves which, I hope, even those who are totally unacquainted with the subject may do with the most perfect ease and accuracy, by the help of this Treatise, which is not published for the purpose of recommending some particular Oculist or of persuading the reader that the simplest of all Optical instruments, spherical Spectacle Glasses, can only be purchased of One Optician:- is not a collection of crude conceits, but is a plain impartial statement of all the Facts I have accumulated during my consideration of the subject for 30 years past in which I have

66

Nought extenuated, nor set down aught in malice."

My Motto, friendly Reader, is

"TRUTH, TEMPERED BY GOOD HUMOUR."