shear-tail 
genus Thaumastura is now usually restricted, the others 
formerly referred to it being placed In Doricha) the struc- 
ture of the tail is peculiar; for the 
middle pair of feathers is so short as 
to be almost hidden by the coverts, 
while the next pair Is suddenly and 
extremely lengthened, and then the 
other three pairs rapidly shorten 
from within outward. In Voricha 
(D. henicura, etc.) the shape of 
the tail is simply forlicate, as 
the feathers lengthen from the 
shortest middle pair to the 
longest outer pair, like a 
Sheartail ( Thaumaslura Cera). 
tern's. In all these cases the long feathers are very 
narrow and linear, or of about uniform width to their 
ends. The peculiar formation is confined to the males. 
T. '"/'/ has the tail (in the male) about 4 inches long, 
though the length of the bird is scarcely 6 inches; It 
is golden-green above and mostly white below, with a 
metallic crimson gorget reflecting blue in some lights, 
and the tail black and white. The female is S\ inches 
long, the tail being i ;. It inhabits Peru. Five species 
of Doricha, range from the Bahamas and parts of Mexico 
into Central America. 
2. A sea-swallow or tern: from the long forked 
tail. See cut under roseate. [Prov. Eng.] 
3. A British shears-moth, as Hadena dentina. 
shearwater (sher'wa'ter), n. [Formerly also 
skeerwater, sherewater; <. shear, v., + obj. ma- 
ter.'] 1. A sea-bird of the petrel family, Pro- 
cellariidie, and section Puffinese, having a long 
and comparatively slender, much-hooked bill, 
short nasal tubes obliquely truncate and with 
a thick nasal septum, long pointed wings, short 
tail, and close oily plumage. There are many spe- 
cies, mostly of the genus Piiffinus, found on all seas, where 
they fly very low over the water, seeming to shear, shave, 
or graze it with their long blade-like wings (whence the 
name). Some of them are known as hags or hagdens. 
Three of the commonest are the greater shearwater, P. 
major; the Manx shearwater, P. anolorum; and the sooty 
shearwater, P.fvliginomt, all of the North Atlantic. They 
nest in holes by the seaside, and the female lays one white 
egg. See cut under ttagden. 
2. Same as cutwater, 3. See lihynchons. 
sheat 1 !, An obsolete form of sheet*. 
Sheat 2 (shet), n. [Prob. a var. of shote? (cf. 
slieafi, var. of shote*). Cf. sheat-fish.] The 
shad. Wright. [Prov. Eng.] 
sheat 3 , >i. An obsolete or dialectal form of 
. 
sheat 4 t, a- [Origin obscure.] Apparently, trim, 
or some such sense. 
Neat, sheat, and fine, 
As brisk as a cup of wine. 
Greene, Friar Bacon, p. 163. 
sheat-fish (shet'fish), . [Formerly also (er- 
roneously) sJieath-fish ; appar. < sheat 2 , a shote, 
+ fisW-.'} A fish of the family Siluridje, espe- 
cially Silurus glanis, the great catfish of central 
and eastern Europe, the largest fresh-water fish 
of Europe except the sturgeons, attaining a 
weight of 300 or 400 pounds. The flesh is edible, 
the fat is used in dressing leather, and the sound yields a 
kind of gelatin. It is of elongate form with a small dor- 
sal, no adipose fin, a long anal, and a distinct caudal with 
a roundish margin ; there are six barbels. It takes the 
place in Europe of the common catfish of North America, 
and belongs to the same family, but to a different sub- 
family. (See cut under Siluridee.) With a qualifying term, 
sheat-fish extends to some related families. See phrases 
following. 
At home a mighty sheat-fish smokes upon the festive board. 
Kingsley, Hypatia, x. (Davits.) 
Electric sheat-fishes, the electric catflshes, or Malapte- 
ruridse. Flat-headed sheat-fishes, the Aspredinida. 
Long-headed sheat-fishes, the Ptenmotidie. Mail- 
ed sheat-fishes, the Luricariidit. Naked sheat-fishes, 
the Pimelodidee. True sheat-fishes, the SUurida. 
sheath (sheth), n. [< ME. shethe, schethc, also 
shede, < AS. scseth, scdth, scedth = OS. scethia, 
seedia = D. scheede = MLG. schede, LG. schede, 
sehee = OHG. sceida, MHG. G. scheide = Icel. 
skeithir, fern, pi., also skithi, a sheath, = Sw. 
5558 
skida, a sheath, a husk or pod of a bean or pea, 
= Dan. skede, sheath: appar. orig. applied (as 
in Sw.) to the husk of a bean or pea, as 'that 
which separates,' from the root of AS. scddaii, 
xceudan, etc., separate : see shed 1 , v. Cf. shide.} 
1. A case or covering, especially one which fits 
closely: as, the sheath of a sword. Compare 
scabbard^. 
His knit he drajh out of his schethe, 
& to his herte hit wolde habbe ismlte 
Nadde his moder hit vnder hete. 
King Horn (E. E. T. S.), p. 104. 
Put up thy sword into the sheath. John xviii. 11. 
A dagger, in rich sheath with jewels on It 
Sprinkled about in gold. 
Tennyson, Aylmer's Field. 
2. Any somewhat similar covering, (a) in bot., 
the part of an expanded organ that is rolled around a stem 
or other body, forming a tube, as in the 
lower part of the leaves of grasses, the 
stipules of the Polygonacex, the tubular 
organ inclosing the seta of mosses, etc. ; 
a vagina ; also, un arrangement of cells 
inclosing a cylindrical body, as the med- 
ullary sheath. See cuts under Eguise- 
turn, exogen, and ocrea. 
The cleistogamic flowers are very small, 
and usually mature their seeds within 
the sheaths of the leaves. 
Darwin, Different Forms of Flowers, p. 
[333. 
(b) In Z"'it., some sheathing, enveloping, 
or covering part. (1) The preputial 
sheath into which the penis is retracted 
in many animals, aa the horse, bull, dog, 
etc. This sheath corresponds in the 
main with the foreskin of man, and is 
often called prepuce. (2) An elytron, 
wing-cover, or wing-case of an insect (3) 
The horny covering of the bill or feet of 
a bird ; especially, a sort of false cere of 
some birds, as the sheathbills, jagers, etc. 
See cuts under pujfin. (4) The lorica or 
test which envelops many infusorians or 
other protozoans, some rotifers, etc. (5) 
lie claws of 
Leaf of l.oliutii 
perennt, show- 
ing sheath. 
The fold of skin into which thi 
a cat or other feline may be retracted, (c) 
In anat., specifically, a membrane, fascia, 
or other sheet or layer of condensed con- 
nective tissue which closely invests a part or organ, and 
serves to bind it down or hold it in place. Such sheaths 
may be cylindrical, as when investing a nerve or blood- 
vessel and extending In Its course ; or flat and expansive, 
as when binding down muscles. A layer of deep fascia 
commonly forms a continuous sheath of all the muscles 
of a limb, as notably in the case of the fascia lata, which 
envelops the thigh, and is made tense by a special muscle 
(the tensor fasciee latse). See/owta, 7. 
3. A structure of loose stones for confining a 
river within its banks. Carotid, chordal, corti- 
cal, crural, femoral sheath. See the adjectives 
Cirrus- sheath. See cirrus. Dentinal sheath of Neu- 
mann, the proper sheath of the dentinal fibers ; the wall 
of the dentinal canaliculi. Also called dental sheath. 
Leaf-sheath, in tat.: (a) The sheath of a leaf. Specifi- 
cally (b) The membranous toothed girdle which sur- 
rounds each node of an Equisetum, corresponding to the 
foliage of the higher orders of plants. See cut under 
Equisetum. Medullary, mucilaginous, penial, peri- 
vascular, rostral sheath. See the adjectives. Pro- 
tective sheath, in bot.. the sheath or layer of modified 
parenchyma-cells surrounding a flbrpvascular bundle. 
Sheath of Henle, a delicate connective-tissue envelop of 
a nerve-fiber outside of the sheath of Schwann, being a 
continuation of the perineurium. Sheath of Mauthner, 
the protoplasmic sheath underneath Schwann's sheath, 
and passing inward at the nodes of Ranvier to separate 
the myelin from the axis-cylinder. It thus Incloses the 
myelin in a double sac. (Ranvier.) The outer leaf be- 
comes thickened about the middle of the internode, in- 
closing a nucleus Sheath of Schwann. Same as /< 
rilemma, or primitive sheath (which see, under primitive). 
Sheath of the optic nerve, that continuation of the 
membranes of the brain which incloses the optic nerve. 
Sheath of the rectus, the sheath formed, above the fold 
of Douglas, by the splitting of the aponeurotic tendon of 
the internal oblique muscle, and containing between its 
layers most of the rectus muscle. 
sheath (sheth),*. /. Same as sheathe. 
sheathbill (sheth'bil), n. A sea-bird of the 
family Chionididse. There are two species, Chionis 
alba, in which the sheath is flat like a cere, and C. (or 
Chionarchtts) minor, in which the sheath rises up like the 
sheave 
pigeon. They are known to sailors as kelp-pigeon and 
sore-eyed pigeon. 
Sheath-billed (sheth'bild), a. Having the bill 
sheathed with a kind of false cere. See shctith- 
bill. 
Sheathclaw (sheth'kla), n. A lizard of the 
genus fhecodactylus. 
sheathe (sheTH), v. t. ; pret. and pp. sheathed, 
ppr. sheathing. [Also sometimes sheath, which 
is proper only as taken from the mod. noun, 
and pron. sheth ; < ME. schethen, sclieden = Icel. 
skeitha, sheathe; < sheath, .] 1. To put into 
a sheath or scabbard; inclose in or cover with 
or as with a sheath or case: as, to sheatlii- a 
sword or dagger. 
Tis in my breast she sheathes her dagger now. 
Dryden, Indian Emperor, Iv. 4. 
Sheathe thy sword, 
Fair foster-brother, till I say the word 
That draws it forth. 
William Morris, Earthly Paradise, II. 273. 
2. To protect by a casing or covering; cover 
over or incase, as with armor, boards, iron, 
sheets of copper, or the like. 
It were to be wished that the whole navy throughout 
were sheathed as some are. Raleigh. 
The two knights entered the lists, armed with sword 
and dagger, and sheathed in complete harness. 
Prescott, Ferd. and Isa., ii. 11. 
3. To cover up or hide. 
Her eyes, like marigolds, had sheathed their light. 
Shak. , Lucrece, 1. 397. 
In the snake, all the organs are sheathed ; no hands, no 
feet, no tins, no wings. Emerson, Civilization. 
4. To render less sharp or keen ; mask; dull. 
Other substances, opposite to acrimony, are called de- 
mulcent or mild, because they blunt or sheathe those sharp 
salu ; as pease and beans. Arbuthnot. 
To sheathe the sword, figuratively, to put an end to war 
or enmity ; make peace. 
Days of ease, when now the weary sword 
Was sheath'd, and luxury with Charles restored. 
Pope, Imit. of Horace, II. I. 140. 
sheathed (sheTHd),^>. a. 1. Put into a sheath ; 
incased in a sheath, as a sword ; specifically, in 
bot., zool., and anat., having a sheath; put in 
or capable of being withdrawn into a sheath; 
invaginated ; vaginate. 2. Covered with 
sheathing or thin material, inside or outside. 
sheather (she'THer), n. [< ME. scJiethere; < 
sheathe + -erl.] One who sheathes, in any 
sense. 
sheath-fish (sheth'fish), n. A false form of 
sheat-fish. Encyc. Brit. ; Web. Int. Diet. 
sheathing (she'THing), n. [Verbal n. of sheathe, 
.] 1. The act of one who sheathes. 2. That 
vhi 
pommel of a saddle. Both inhabit high southern lati- 
tudes, as the Falkland Islands and Kerguelen Land; the 
plumage is pure-white, and the size is that of a large 
which sheathes, covers, or protects, or may be 
used for such purpose. Specifically (a) In carpen- 
ter-work, boarding applied to any surface, or used to cover 
a skeleton frame ; especially, such boarding when forming 
the inner or rough covering intended to receive an outer 
coating of any sort, (b) Thin plates of metal used for cov- 
ering the bottom of a wooden ship, usually copper or yel- 
low metal, and serving to protect it from the boring of ma- 
rine animals ; also, a covering of wood applied to the parts 
under water of many iron and steel vessels, to prevent cor- 
rosion of the metal and to delay fouling of the bottom, (c) 
Anything prepared for covering a surface, as of a wall or 
other part of a building : applied to tiles, metallic plates, 
stamped leather hangings, etc. 
Mural sheathinffs imitative of the finest Persian patterns. 
Art Jour.,X. S., VII. 36. 
(a) A protection for the main deck of a whaling-vessel, as 
pine boards, about one inch in thickness, laid over the deck 
to prevent it from being cut up by the spades, being burned 
while trying out oil, etc. 
sheathing (she'THing), p. a. Inclosing by or 
as by a sheath : as, the sheathing base of a leaf; 
sheathing stipules, etc. See cut under sheath, 2. 
Sheathing canal. See canali. 
sheathing-nail (she'THing-nal), . A nail suit- 
able for nailing on sheathing. That used in nail- 
ing on the metallic sheathings of ships is a cast nail of an 
alloy of copper and tin. 
sheathing-paper (she'THing-pa^per), n. A 
coarse paper laid on or under the metallic 
sheathing of ships, and used for other like pur- 
poses; lining-paper. 
sheath-knife (sheth'nif), n. A knife worn in 
a sheath attached to the waist-belt, as by mer- 
chant seamen and by riggers. 
sheathless (sheth'le's), a. [< sheath + -less.'] 
Having no sheath ; not sheathed ; evaginate. 
sheath-winged (sheth'wingd), a. Having the 
wings sheathed or incased in elytra, as a beetle ; 
sharded; coleopterous; vaginipennate. 
sheathy(she'thi), o. [< sheath + -#!.] Sheath- 
like. Sir T. Browne, Vulg. Err., iii. 27. 
shea-tree, . Same as shea. 
sheave 1 (shev), '. t. ; pret. and pp. sheared, ppr. 
shearing. [< xheuf 1 , n. Cf. sheaf 1 , c., and 
