maticism I attribute in great measure its power of very distinctly shewing the division in the Ring of Saturn.

The visibility of the dark line, which proves the Ring to be double, depends not only upon the distinctness of the image formed by a Telescope, but on the power it has to shew a white object quite white, and a black one, black.

When Saturn is near the meridian, the division in its Ring is most plainly visible but it may generally be observed Two, and in very fine Nights, Three hours, before it comes to the Meridian.

Those who wish to see this in London, are advised that they will not discern the division in the Ring half so well before-as after 10 o'Clock.

In this "Elysium of Bricks and Mortar" we are so surrounded by "Groves of Chimneys," that until the majority, of the Great Fires of the great Manufactories are out - the obfuscated atmosphere of this monstrous metropolis defies all the penetrating power that the immortal Herschell himself could bring against it.

Objects which require all the powers of the Eye to be fresh, and in fine condition, should

not be examined when that Organ is tired with having been at work all Day.

If a Planet comes to the Meridian at Midnight, at 9 or 10 o'Clock lie down in a quiet darkened room, and rest your Eye by getting a nap previously. A little Horizontal Refreshment, you will find a proper and renovating preparative for such Contemplation; halfan-hour's Siesta will restore the tone of your Visual Organs, and sharpen your Sight prodigiously.

"Experto Crede."

I also saw the small Star near the Polar Star with my Beauclerc Telescope, which has a triple Object glass of 46 inches focus, with a Lens of the 22d of an inch focus, which gave this Glass a power of 1012 times.

This singularly perfect Telescope, which shews Stars as stark neat as ever Nature permitted them to be seen;-I purchased at the sale of Mr. Aubert's Instruments, when they were sold at his Observatory, at Highbury Place, by Mr. S. Sotheby, July 24th, 1806:—it was originally fitted up for the Honourable Topham Beauclerc, and Mr. Ramsden's name is engraven on the Eye-end of the Telescope - but Mr. Peter

Dollond informed me that he made the Object Glass and smiling at the time he gave me this information, said, "Yes, that Object Glass is one of the things which is to make me immortal," and I then gave him permission to engrave his title thereto on the tube of the Telescope.

To have produced such a perfect Instrument is so honourable to the talent of the artist, that, to avoid all appearance of prejudice to either of these eminent men, I have called it by the name of the person it was made for, Beauclerc.

In the Second Part of " THE ECONOMY OF THE EYES," which is now preparing for the Press,

"Paulo majora canamus”

the Illuminating and Magnifying Powers of NEWTONIAN, GREGORIAN,CASSEGRAINIAN, HERSCHELIAN Reflectors, and GALILEAN, HUGHENIAN and ACHROMATIC Refracting TELESCOPES of various sizes,—will be explained by Experiments made with 46 Telescopes of from 3 Inches to 7 Feet focus, which I purchased for that purpose, and have cost me upwards of £1200; and which all who

have Instruments of the like dimensions, may easily verify at the expense of a few shillings.

A circumstantial account will be given of their several performances and powers, as Astronomical and Day Telescopes, — being the results of 30 years' observation.

Concave

To enable my Readers to measure the respective merits, and the relative reflective powers of Convex, and Plane Small Specula-I shall lay before them, an abstract of their several pretensions as stated by preceding writers thereon; then proceed with those Practical Observations which I have made myself, and those which I have been favoured with by several scientific Opticians, and amongst them those experienced and excellent Makers of Reflecting Telescopes, Messrs. Watson - Tulley -- and Cuthbertwho have given me their Notes and Observations thereon, and the account of the Facts which they have actually ascertained in the course of their numerous experiments with Telescopes of various constructions. I have only room in this page to add, that the Opinions of these eminent Practical Opticians are perfectly unanimous, and in perfect unison

with those published by Sir I. Newton,—and that I believe, that their Evidence and Arguments are so true, and so convincing, and so plainly stated, that they will be perfectly satisfactory to the Reader, and will finally settle certain important points, which without such Illustration, seem to me, likely to remain as they are at present

"Puzzled with Mazes, and perplexed with Errors."

I shall also give an account of the invention and advantages of the PANCRATIC EYE-TUBE, which to a 3 Achromatic, gives in the most perfect manner every degree of Magnifying power from 100 to 400 times-which will be minutely described and explained by Engravings. N. B. Contributions on Optical Subjects, ad

dressed to the Publishers of this Work, will be gratefully acknowledged.

I have mentioned my own case of dimness of Sight, because, I believe many Artists, from the want of such a hint, have greatly injured their Eyes, by having been induced by similar Symptoms, prematurely to put on Spectacles: but, in such cases," Rest is the best Remedy."

"So great is the calamity entailed upon the