The last thing I did, before leaving, was to uncap the lens; and after that I went off to my bedroom, and to bed; for I intended to be up at midnight; and to ensure this, I set my little alarm to call me; also I left my candle burning.

Light which enters the collimating lens partly passes through the prisms and is partly reflected from the first surface of the prism; that we utilize, thus giving a second shadow.

" He handed me the lens and I scrutinised every part of each hand without being able to detect the faintest trace of any recent wound.

The apparatus consists of three parts, A, B, and C. A is rigidly fixed; it contains the dark slide and the contrivances by which the position of the image can be viewed; the eye-hole, e, already mentioned, being part of A. B is a travelling carriage that holds the lens, and is connected by bellows-work with A.

In the centre of the floor and in that of the roof respectively I placed a large lens of crystal, intended to act as a window in the first instance, the lower to admit the rays of the Sun, while through the upper I should discern the star towards which I was steering.

The author has had constructed a cylindrical lens in which the axis remains constant in direction and amount of refraction, while the refraction in the meridian at right angles to this varies continuously.

The portion behind the iris forms the posterior chamber, and contains the crystalline lens and a transparent, jelly-like fluid, the vitreous humor.

One of the easiest ways of accomplishing this double purpose is to cut a convex lens through the middle, grind the curves of the two halves down to straight lines, and join them by their thin edges.

The major directed a careful lens at this survivor.

With a trembling hand, I drew out my lens to examine it more closely; and, as it came into the magnified field, my heart seemed to stand still.

I waited till I thought they were 'most across, and then I rubbed the lens.

A materialistic friend suggested that he was adjusting the focus of his wonderful eyes, and the action was certainly like that of an optician examining a lens; but I feel that there was something more ceremonial about it.

" I focussed the lens on the flush-cut surface of closely-rolled leaf, and explored every part of it minutely.

" He handed me his lens, and, when I had verified his statement, he produced from his pocket a small tin box with a closely-fitting lid in which he deposited the paper, having first folded it up into a small parcel.

I snatched out my lens and brought it to bear on those astounding impressions.

However, it will be near enough for our purpose if you get a sharp image of the sun on a piece of paper, and while you hold lens and paper, get some one to measure the distance from the paper to the diaphragm aperture, or, in the case of a single lens, to the center of the lens.

Thus, while the whole effect of the picture is brilliant and harmonious, we shall find, on taking a lens, that we can count every individual bead in the chaplet of the monk who is one of the more conspicuous reliefs on the sarcophagus.

FRESNEL, AUGUSTIN JEAN, French physicist, born at Broglie, Eure; as an engineer he rose to be head of the Department of Public Works at Paris; in 1825 he was elected an F.R.S. of London; he made discoveries in optical science which helped to confirm the undulatory theory of light, also invented a compound lighthouse lens (1783-1827).

Newton surmounted this difficulty by laying a double convex lens, the radius of the curvature of each side of which was fifty feet, upon the flat surface of a plano-convex object-glass, and in the way he obtained a plate of air, or of space, varying from the thinnest possible edge at the centre of the object-glass where it touched the plane surface to a considerable thickness at the circumference of the lens.

On August 25th I made experiments on my left eye, with good measures, and on Aug. 26th ordered a cylindrical lens of Peters, a silversmith in the town, which I believe was never made.

A limit is soon reached, however, for the quantity of light received diminishes very rapidly as the revolving mirror approaches the lens.

He produced from his pocket a powerful doublet lens, with the aid of which he examined every part of the surface of the cigar, and finally, both ends.

Two such lenses mounted with axes parallel and with curvatures varying in opposite directions produce a compound cylindrical lens, whose refraction in the direction of the axes is zero, and whose refraction in the meridian at right angles to this is at any point the sum of the refractions of the two lenses.

Above the box, which was about two and a half feet square, was an electric motor from which ran a belt connecting with the inner mechanism; from the front of the box protruded the lens, its glassy eye so turned as to get a full sweep of the track; nearby on the ground were piled the storage batteries which were used to supply the current for the motor.

Then he pulled over me a great movable lens as of a microscope, which concentrated the insupportable light.