lens 
(Sec focus, I.) A concave lens always renders still more 
divergent rays emanating from a point and so forms only 
VIM iial foci. If the source of li^ht is an extended *u 
then the pencil of rays emanating from farh point forms 
its own focus; and the collection of foci constitutes an 
imw.ie. which is real and inverted if the foci are real, but 
virtual and erect if they are virtual. The relative sizes 
of the object and image are sensibly proportional, if the 
lens is thin, to their respective distances from the optical 
center; if the lens is thick, the distances must be reck- 
oned from the two so-called principal points of the lens 
(see priiKipal point, under point), which lie on the axis 
on each side of the optical center. An image formed 
by a single lens is never perfectly distinct, on account of 
the spherical and chromatic aberrations of the lens. (See 
aberration, 4.) The former is due to the fact that a lens 
bounded by spherical surfaces converges marginal rays 
to a point nearer the lens than that in which the central 
rays meet; the latter, to the fact that rays of different 
color form their foci at different distances, the focal dis- 
tance for violet rays being (with a glass lens) nearly a 
seventh part shorter than that for the red rays. The 
spherical aberration can be corrected by making the sur- 
faces of forms other than spherical, or by combining two 
or more lenses properly proportioned; the chromatic 
aberration, only by combining two or more convex and 
concave lenses of different materials, usually a convex of 
crown-glass with a concave of fiint-glass. 
2. In linn /.. in the eye, a double-convex body 
placed in the axis of vision behind the iris be- 
tween the aqueous humor and the vitreous hu- 
mor, serving to focus rays of light upon the 
retina ; the crystalline lens. See first cut under 
eye 1 . 3. Figuratively, photography, from the 
use of lenses in that art. 
So thoroughly has this region been set forth by the pen 
and the pencil and the lent that I am relieved of the ne- 
cessity of describing it Uarper's Mag., LXXVIII. 258. 
4. [cap.] [NL.] A genus of leguminous plants of 
the tribe Vicie<e. Jt is distinguished from Vicia by hav- 
ing but two ovules instead of many, as is generally the case 
in Vicia. The 8 species enumerated by some are gener- 
ally reduced to 2, which are low erector half -climbing herbs 
with pinnate leaves and small single or racemose pale- 
blue flowers, natives of the Mediterranean region and 
eastern Asia. One species, Lens esculenta, the seeds of 
which are called lentil*, ia probably one of the oldest of 
plants cultivated by man for food. See lentil. Achro- 
matic lens. See achromatic. Actinic lens, a com- 
pound lens so constructed that its chemical and lumi- 
nous foci coincide. AplanatiC lens, a compound lens 
in which both chromatic and spherical aberrations are 
corrected. Apochromatic lens, a microscope-objective 
made from certain peculiar kinds of glass, by means 
of which the aberrations can be more accurately cor- 
rected than in lenses made of the ordinary crown- and 
flint-glass. Burning-lens, a convex lens used to con- 
centrate the heat of the sun at its focus. Camera-lens, 
a combination of lenses used in a camera obscura. See 
camera. Capsule of the lens. See capsule. Carte- 
sian lens. See Cartesian. Coddlngton lens, a lens 
formed from a sphere of glass by cutting a deep and wide 
equatorial groove around it, and filling the groove with 
some opaque substance. Colllmating lens. See col- 
l ,'m,, tut'/ Concave lens, a lens that is thinner at the 
center than at the edge. Condenslng-lens, or con- 
denser, a convex lens or a combination of lenses used to 
concentrate a strong light upon some point or surface, 
as upon the slit of a spectroscope or a microscopic object 
or a photographic negative in the process of making an 
enlarged picture. Convex lens, a lens that is thicker 
at the center than at the edge. Copying-lens, a photo- 
graphic lens specially designed for copying engravings, 
etc. Crossed lens, a glass lens the spherical surfaces of 
which have radii bearing the ratio of 1 toe. It has less 
spherical aberration than any other form of glass lens 
with spherical surfaces. Crystalline lens. See def. 2, 
crystalline, and eyei, 1. Cylindrical lens, a lens which 
has one or both surfaces cylindrical : commonly used in 
eye-glasses to correct astigmatism of the eye. See agUg- 
mottnn. Diamond lens, a lens made from a diamond. 
Doublet (lena), a combination of two lenses separated 
by a small distance. Sometimes each of the two is itself 
compound. Field lens, in an eyepiece, the lens which 
is furthest from the eye, and has the special function of 
enlarging the field of view. Fluid lens. See fluid. 
Fresiiel lens, a lens (hearing the name of its inventor) 
formed of a central plano-convex 
^^tf^IZIZr'jLjSsI^ lens surrounded by segmental rings, 
all having the same focus. The 
" separate pieces are cemented to a 
plane glass or set in a metal frame. (Fig. 4 represents 
the cross-section of such a lens.) It is used in lighthouses 
and signal-lamps. Immersion-lens, a microscope-ob- 
jective which requires a drop of water or other liquid to 
be put between it and the cover of the object under ex- 
amination, thus increasing the angle of aperture and ob- 
viating loss of light by reflection. Landscape lens, a 
photographic lens specially adapted to landscape photog- 
raphy. Magnify ing-lens, a lens used to Increase the 
apparent size of 
an object seen 
through it A 
convex lens held 
near the eye pro- 
duces this effect 
when the dis- 
tance of the ob- 
ject from the lens 
is less than the 
principal focal 
length of the lens. 
(0 F in fig. 5.) The rays from the object A B, after passing 
through the lens, reach the eye as if they came from the vir- 
tual image a b. Multiplylng-lens, a plano-convex lens 
the convex side of which has been worked into a number 
of plane facets, each of which presents a separate image 
(virtual, and not magnified) of the object viewed through 
it Orthoscoplc lens, a form of achromatic doublet 
3409 
giving n very flat and nndUtorted field of view. Perl- 
BCOiilc lens, a lens with * very wide field of view. The 
numr is specially applied to up, ctai-lr-lrnsi-s which me 
concave on the surface next the eye ; also to some wi.lr 
angle photographic lenses. Photographic lens, a lens 
or combination of tenses adapted for photography. Ordi- 
narily the lens of the photographic camera is a combination 
of two achromatic lenses of pe- 
I collar curves, mounted In a tube 
with a considerable space be- 
tween them. (See fig. 0.) The 
photographic objective of a tel- 
escope is like an ordinary achro- 
matic objective, except that its 
curvet are adjusted to bring the 
blue and violet rays to the most 
accurate focus possible, rather 
than the yellow and green rays, 
Fig. 6. Photographic 1-em 
(Type of Portrait Kens). 
which are most effective in vision. Polyzonal lens. 
Same as Fresnel lent. Portrait-lens, a photographic 
lens specially adapted to the taking of portraits. Rec- 
tilinear lens, a photographic lens so constructed that 
straight lines in the object will not be distorted Into 
curved lines in the picture. Side-condensing lens, a 
condensing-lens so attached to a microscope as to illumi- 
nate an opaque object by side-light Stanhope lens, a 
lens of small diameter with two convex faces of different 
radii, Inclosed in a metallic tube. Triplet lens, a . om- 
bination of three lenses, usually all achromatic. The or- 
dinary form of microscope-objective is a triplet Wide- 
angle lens, a photographic lens capable of making a dis- 
tinct and undistorted picture of objects which subtend 
angles of 60' to 100" or more as seen from the camera; 
also, a microscope-objective which admits from each point 
of the object a pencil of rays of wide angle (often as much 
as 140" and upward); an objective of large angular aper- 
ture. See aperture, 4. 
lens-cap (lenz'kap), n. A cap or cover fitting 
over the opening of the tube of a lens. 
lens-holder (lenz'hol'der), n. A device for 
supporting a lens, or a combination of lenses, 
during the adjustment to the focus of an ob- 
ject on an adjustable forceps or stage below. 
E. H. Knight. 
Lent 1 (lent), n. [< ME. lent, lente, an abbr. of 
lenten 1 , the final syllable being appar. taken 
as inflexive: see lenten 1 .] An annual fast of 
forty days, beginning with Ash Wednesday and 
continuing till Easter, observed from very early 
times in the Christian church, in commemora- 
tion of Christ's forty days' fast (Mat. iv. 2), and 
as a season of special penitence and preparation 
for the Easter feast. The lenten fast is now observed 
as obligatory by the Orthodox Greek and other Oriental 
churches, and by the Roman Catholic, Anglican, and Lu- 
theran churches, and as a profitable exercise by many mem- 
bers of other churches. It has varied in length at different 
times and in different parts of the church, and has begun 
later or earlier according as Sundays only or Saturdays also 
were excepted from fasting. In the Western Church it 
begins on Ash Wednesday, forty-six days before Easter ; 
but as the Intervening Sundays, called Sundays in (not of) 
Lent, are (on the ground that Sunday is always a feast- 
day) not counted part of Lent the fast lasts only forty 
days. The first Sunday In Lent is known as Quadragenima 
Sunday, the fourth as Mid-Lent Sunday, the fifth as Pas- 
sion Sunday, and the sixth (beginning Holy Week) as Palm 
Sunday. The two weeks and a half preceding Lent, be- 
ginning with Septuagesima, following which are Sexagesi- 
ma and Quinquagesima Sundays, form the pre-lenten 
season, a transition between the joyful Christmas and 
Epiphany season and the penitential season of Lent. In 
medieval times the name Lent (or, in Latin, Quadragesi- 
ma) was given to other periods of fasting also. Forty days 
between Martinmas (November llth) and Christmas Eve 
were called St. .Martin* Lent (Quadragesima S. Martini), 
and another Lent preceded St John Baptist's day (June 
24thX In distinction from these, the period between Ash 
Wednesday and Easter was called Great Lent and Clean 
Lent, the last name being probably given on account of 
the preceding confession and absolution. In the Greek 
Church Lent (Teero-npo/coo-nj) begins on the Monday after 
Tyrophagus (Quinquagesima), and the first third, and 
sixth Sundays are called Orthodoxy Sunday, Stauroproricii- 
netimos (Sunday of the Adoration of the Cross), and Palm 
Sunday respectively. 
If it may be, fast 
Whole Lents, and pray. 
Tennyson, St. Simeon Stylites. 
Great Lent, Great fast, in the Or. Ch., the lenten fast, 
as the most important fast of the year, in distinction from 
other seasons of fasting, to which the name Lent (as equiva- 
lent to T(7o-ap<utoo-Tii) Is also given by Western writers : 
namely, that between St Philip's day (November 14th) 
and Christmas (Fast of St Philip or of the nati vity j. that 
after All Saints' Sunday, which corresponds to the Western 
Trinity Sunday (Fast of the Apostles), and that from August 
1st to the 14th, the eve of the Repose of Theotocos (Fast 
of the Theotocos). Head of Lent. See head. Lent 
collectors. See collector, 5. Lent determination. See 
determination, 12. 
lent 2 (lent). Preterit and pastparticiple otlend 1 . 
lent 3 (lent), a. [< OF. and F. lent = Sp. Pg. It. 
lento, pliant, flexible, tenacious, slow, sluggish, 
easy, calm, < li.lentus (in form as if contr. of 
lenitus, pp. of lenire, soften), < lenis, soft, smooth, 
gentle, akin to E. lithe: see lenity, lenient, etc., 
tm&leath 1 , lithe 1 . Hence relent.] If. Slow; gen- 
tle; mild. 
We must now Increase 
Our fire to ignis ardens : we are past 
Kinius equimis, balnei cineris, 
And all those lenter heats. 
/;. Johnson, Alchemist, iii. 2. 
2. In music, same as lento. 
lenticnla 
lentando (len-tan'do), ailr. [It., ppr. of Irn- 
1'iri, make slow, < lento, slow : see lent 1 *, a.] In 
music, slackening; retarding: a direction to 
singorplay with increasing slowness the notes 
IIVIT which it is writtrii. 
lentet, . [ME., < OF. Irate, < L. len(t-), a len- 
til: HOC Icnx, l<-iitil,] A lentil. H'yrlif. 
lenten 1 (len'ten), n. and a. [< ME. lenten, rare- 
ly lenton, leinten (also abbr. lente, leinte, whence 
mod. E. lent), < AS. lencten, lengten, rarely lenten 
( = D. lente = MLG. lente, lenten, linte = OHO. 
n, lengizin (in lengizinnianoth), also lento, 
MHO. lenze, Q. lenz), the spring, later applied 
esp. to the fast beginning in the spring, called 
in full lenctenfasten, i. e. ' spring-fast, usually 
derived < lang, long (whence also length and 
lengthen), "because the days become longer in 
spring": see long 1 , a. This derivation is sup- 
ported by the var. forms OHG. langiz, Mll< .. 
langes, langeze (ujipur. < lang, long); but the 
deriv. is irreg. in form and thought, and the 
OHO. MH6. var. forms may be due to popular 
etymology. It is not probable that the word 
ia connected with long. In mod. use lenten as 
a in HIM is abbr. to lent, while in attrib. use it re- 
mains unchanged, being taken as an adj. in 
^w 2 .] I.t 1. The spring; the season follow- 
ing winter. 2. A fast observed in the spring: 
same as Lent 1 (of which lenten is the older form). 
To leue ne to lere, ne lenlenu to faste. 
Piers Plowman (C), xlv. 81. 
II. a. [cap. or I. c.] 1. Pertaining to Lent; 
used in Lent: as, Lenten sermons; the lenten fast. 
And perhaps it was the same politick drift that the Div- 
ell whipt St Jerom in a lenten dream, for reading Cicero. 
MUton, Areopagitica, p. 14. 
Hence 2. Characteristic of or suitable for 
Lent; spare; plain; meager: as, lenten fare. 
If you delight not in man, what lenten entertainment 
the players shall receive from you. 
Skat., Hamlet, ii. 2. 820. 
Who can read 
In thy pale face, dead eye, and lenten suit, 
The liberty thy ever-giving hand 
Hath bought for others? 
Beau, and Fl., Honest Man's Fortune, Iv. 1. 
Meanwhile she quench'd her fury at the flood, 
And with a lenten sal hid cool'd her blood. 
Drydtn, Hind and Panther, III. 27. 
3f. Cold; austere: as, a lenten lover. Com- 
pare Lent-lover. Cotgrave Lenten flg, a dried fig ; 
a raisin. Lenten hearse. Same as tenema-heant. 
Lenten veil, a curtain formerly suspended in the West- 
ern Church before the high altar during Lent and said to 
be still in use in Spain. It was a survival of the primitive 
amphithyra, retained in the Greek Church. 
lenten'-* (len'ten), n. A dialectal variant of 
linden. 
lenten-crab (len'ten-krab), n. A fresh-water 
crab of southern Europe, Thelphusa ftutiatilis, 
allowed to be eaten in Lent. 
lenthet, n. A Middle English form of length. 
Lentibulariese (len-tib-u-la-ri'e-e), n. pi. [NL. 
(Lindley, 1845), < Lentibularia (said to be ( irreg. ) 
< L. lens (lent-), a lentil, + tubttltts, a small pipe 
or tube), old name for Utricularia, + -ece.] An 
order of dicotyledonous gamopetalous plants 
of the cohort Personates, distinguished by the 
one-celled ovary containing a free central pla- 
centa. See Utricularia. 
lenticel (len'ti-sel), . [Also lenticelle ; < F. 
leitticelle, dim. of lenticule, lens-shaped: see len- 
ticule.] 1. In hot., a lens-shaped body of cells 
formed in the peridenn or corky layer of bark, 
which by its enlargement soon ruptures the 
epidermis, or the older corky layers where such 
are present. Outwardly lentlcels appear In the earliest 
stage merely as brighter spots, then as oval warts, becom- 
ing two-lipped; while in some plants they widen with the 
growth of the stem into transverse stria?. They are pro- 
duced either beneath a stoma or group of stomata or in- 
dependently. Their intercellular spaces are In commu- 
nication with the outer air, and they thus serve the pur- 
pose of cortical pores, which name they sometimes bear. 
The outer (not corky) cells of a lenticel are termed packing 
or complementary celis; the inner (corky) cells have been 
called phellem. Lenticels occur on the great majority of 
stems which produce bark in annular layers, also on the 
footstalks of many ferns. 
2. In mutt., one of the small mucous crypts or 
follicles of the base of the tongue having the 
shape of a lentil; a lenticular gland. 
lenticellate (len-ti-sel'at), a. [< lenticel + 
-ate 1 .] Pertaining to or having lenticels. 
lenticelle, n. See lenticel. 
lenticula (lrn-tik'u-18), .; pi. lenticula (-le). 
[L., a lentil, a lentil shape, a vessel of lentil 
shape, a freckle: see lentil, lenticule.] 1. In 
optics, a small lens. 2. In hot.: (a) A lenti- 
cel. (6) The spore-case of some fungi. 3. A 
freckle; an epnelis. 
Also fe timle. 
