There are some perfectly authenticated instances of persons possessing the faculty of Sight as to the perception of Form—who had no sense of Colours-others who could not distinguish their difference by Candlelightand one I have met with who by Daylight cannot tell Red from Green-but recovers the power of discerning them correctly by Candlelight. The latter is a very singular anomaly of Vision.

THE

CUMUMBRA & SEMIUMBRA LAMPS,

Made at DEVILLE'S Manufactory, near Exeter 'Change, Strand.

THE shade of this Lamp is so contrived that it completely prevents any of its rays coming

changed in the same proportion. But if in the day-time you place Candles in a darkened chamber that every thing therein may be well illuminated, and then retire to another place illuminated with the Sun's light-the Objects illuminated with Candlelight, when viewed through the door of the room, will appear tinged with a yellow red, when compared with those that are seen at the same time illustrated with Daylight."-Dr. PORTERFIELD on the Eye, 8vo. 1759, Vol. I. p. 127.

to the Eyes- the pupil of which is therefore regulated solely by the object under examination. Every part of the Frame, &c. is coloured a dead black.

The faults of all the other Reading Lamps which I have seen, are, that the shade does not come either high or low enough to completely shade the light and at the top is partly composed of fretwork which shows the light through it and the frames are frequently painted with a light colour, and highly varnished.

To this Lamp may also be fixed a Half shade, which will screen the Light from the person reading, and at the same time light the Room which in some cases is a very desirable

contrivance.

It is so simple in its construction, that it is not liable to get out of order, and there is very little more trouble in trimming it for Seven hours, than there is in Once snuffing a Candle.

It is not only cheap in the purchase, but in use, for I think it affords more light than Two Candles at the cost of One. The Oil reservoir holds three-fourths of half a pint of Oil, which at the present price of the very best Lamp Oil,

(5s. 6d. per Gallon,) costs 3 pence, which divided by 12, (the number of hours it will burn,) gives the expense of this Light, i. e. A Farthing per Hour.

The Light of the Cumumbra is so good, that Persons whose Sight is beginning to fail, and who cannot read by Candlelight without Spectacles of 36 inches focus, with this Lamp read as well as they can by Daylight; and so it deserves all the praise which the pickpocket gave to the Gas light-"It is as bad as Daylight!”—i. e. for Opticians; for by the help of this Lamp persons may read a year or two longer than they would be able to do without -and always, with Glasses of the same magnifying power which they use by Day.

The effect of a strong Light* I have seen evidenced by the fact that Persons who have many years used Spectacles, when the Sun shines on their Book, can see without.

I believe, that the main Reason why the Sight

* "A person who has been obliged for some years to use Spectacles in reading, will, in the Sunshine, be able to read very easily without them."-Dr. PORTERFIELD ON the Eye, 8vo. 1759, Vol. I. p. 162.

is not so sharp at Night as it is in the Morning, is, that the Eyes are tired, by having been at work all Day.

The sensibility of the Sight is surprisingly recruited by Sleep. Dr. Porterfield, in p. 38 of Vol. II. of his Essay on the Eye, observes, "the Pupil is very large upon our first awaking."

I have for many years been accustomed to sleep with a light in the Room — and if at any time it has gone out, I have generally awoke just time enough before to previously light a Candle and have often wondered, that the diminution of so faint a light had such a strong effect on my Eye, as to awaken me out of a sound Sleep.

I read the above neer, and he said

to Mr. BUNDY the Engi"The very same thing happens to me - I always awake just before my Night Lamp goes quite out."

The best Light for burning all night is the Semiumbra Chamber Lamp, this may be set with perfect security on a Table by the Bedside within reach, and by turning it half round, you

* Made by DEVILLE, near Exeter 'Change, Strand.

may in a moment, have either Light or Shade a frame -may be made to carry it over a Bainmarie Saucepan, like the Nursing Lamps for keeping children's food warm, which will keep half a pint of Tea or Broth warm all Night. This will be a great Comfort to Invalids- especially to those afflicted with Nightmare, for which a draught of hot water will give more immediate, and more permanent relief, than any remedy I have tried.

See the Author's own Case in pages 206 to 214 of "THE ART OF INVIGORATING LIFE," 4th Edit. 12mo. 1822. Published by HURST and Co. No. 90, Cheapside.

The strongest objection to Candlelight is, that the degree of Light given by A Candle, and its distance from the Eye, is varying every moment;-A Lamp has not this disadvantage : by merely bringing it nearer to, or removing it farther from the object under examination, its Light may be either increased or diminished, and may be adjusted to almost any degree; and it will several hours.

continue the same for

Those who cannot recollect having played so much with a new Plaything, "and fancied