thalassographic 
The Held of work opened to naturalists by i 
graphic surveys is of the greatest Importance. 
A. AyaHxiz, Tlireu Cruises of the Itlake, 1. vii. 
thalassography (thal-a-sog'ra-li), n. [Of. MGr. 
tlu'/tinnii; JUI^IIH ;, Jeseribiiij; t lie sea ; <(>r. Ihi/.tioaa, 
the sea, + j^ii^r/i 1 , write.] The science of the 
ocean; oceanography; that branch of physical 
geography which has to do with the phenomena 
of the ocean. 
The need of some simple word to express the science 
which treats of oceanic basins lias led to the construction 
of this term [thalfln>ti)(fT(iphif\. 
A. AyuKHij, Three Cruises of the Blake, I. i. 
thalassometer (Hml-a-som'o-ter), M. [< Gr. 
iin/iinmi, the sea, + utrpw, measure.] A tide- 
gagf. 
Thalassophila (thal-a-sof'i-lii), . pi. [NL., 
neut.pl. of 'tlialamophilii.i: see t/tn lassOpkUOHt.] 
A suborder or other group of pulmonate gas- 
tropods, living on sea-shores or in salt-marshes, 
as the WpkoMrMdlB and .tni/>hibolidx. 
thalassophilous (thal-a-sof'i-lus), a. [< NL. 
"thalaxiHiiiliilitu, < Gr. HA'/.aaaa, the sea, + ij>t).eiv, 
love.] Fond of the sea; inhabiting the sea: 
specifically noting the Thalassophila. 
thale-cress (thalTcres), n. [< "thale (abbr. < 
Tluiliaiia: see def.), so called from a German 
physician Thai or Thaliux, + cress.'] The mouse- 
ear cress, fii.il/iii/iriiiiii Thaliana, a low slender 
herb of the northern Old World, naturalized in 
the United States. 
Thaleichthys(thal-e-ik'this), H. [NL. (Girard, 
1859), < Gr. tial.ua, blooming, + i^c, a fish.] 
A genus of argentiuoid fishes, related to the 
smelts and caplins. T. pacificus is the candle- 
fish or eulachon. See cut under candle-fish, ]. 
thaler (ta'ler), . [< G. thaler, a dollar: see 
dollar.-] A 
large silver 
coin current 
in various Ger- 
man states 
from the six- 
teenth cen- 
tury. The tha- 
ler of the present 
German empire 
is equivalent to 
three marks, and 
Is worth about 
3& English (72 
cents). 
Thalessa(tha- 
1. Asubgenus 
of Purpitni. 
Adams, 1858. 
2. A curious 
genus of ich- 
neumon-flies, 
of the sub- 
family Pim- 
plinse, notable 
for their size 
and the great 
length of the 
ovipositor. The 
larvm live exter- 
nally upon those 
of horntails and 
wood-boring bee- 
tles, and the long 
ovipositor of the 
adult enables it 
to bore for a con- 
siderable distance through solid wood. T. atrata and T. 
tunntor are common parasites ot Tremex columba iu the 
lulled States. Holmgren, 18511. 
Thalia (tha-li'ji), . [= F. Thalie, < L. Thalia, 
sometimes Thalea,<.Qr.Qafeia, one of the Muses, 
< tfn/ria, luxuriant, blooming, < ffdi'/.eiv, be luxu- 
riant or exuberant, bloom.] 1. In (Jr. myth., 
the joyful Muse, to whom is due the bloom of 
life. She Inspired gaiety, was the patroness of the ban- 
quet accompanied by song and music, and also favored 
rural pursuits and pleasures. At a late period she became 
the Muse of comedy, and to the Romans was little known 
in any other character. In the later art she is generally 
represented with a comic mask, a shepherd's crook, and a 
wreath of ivy. See cut in next column, and cut under 
mask*, i. 
2. The twenty-third planetoid, discovered by 
Hind in London iu 1852. 3f. In zool. : (a) A 
genus of salps, giving name to the Thalix or 
Tliii/inciti : same as Sal/>a, 1. (b) A genus of 
coleopterous insects. Hope, 1838. 
Thaliacea (tha-li-a'se-a), . pi. [NL. (Menke, 
1830), < Thalia (in allusion to its phosphores- 
cence: see Thalia) + -<v.] A division of 
tunicates, containing the free-swimming forms, 
or the salps and doliolids : distinguished from 
A.iriiliafi'a. Also Thaliir, Thaliudie, Thalida, 
Thai i i !(.. 
Reverse. 
Thaler of LQneburg. 1547. British Museum. 
(Size of original.) 
thaliacean. (tha-li-a'se-an), a. and w. I. a. Of 
or pertaining to the lhaliacea. 
II. n. A member of the Thaliacea, as a salp 
or doliolid. 
Thalian (tha-li'an), a. and w. [< Thalia + 
-an.] I. a. 1. Of or relating to Thalia, espe- 
cially considered as the Muse of pastoral and 
comic poetry; comic. 2. [<". e.] In 067., same 
as thaliacean. 
II. n. Same as thaliacean. 
Thalictrtun (tha-lik'trum), . [NL. (Tourne- 
fort, 1700), < L. thalictrum, thalitruum, < Gr. 
6al.iK.Tpav, a plant, prob. Thalictrum minus ; per- 
haps so called from the abundant early bright- 
green foliage, < OdM.etv, be luxuriant : see thai- 
lug."] A genus of plants, of the order Ranuncu- 
laeeee and tribe A nemoneee. It Is distinguished from 
the similarly apetalous genus Anemone by its lack of an in- 
volucre. It includes about 70 species, mostly natives of 
the north temperate or frigid regions, with a few In tropi- 
cal India, the Cape of flood Hope, and the Andes. They 
are delicate or tall herbs with a perennial base, and orna- 
mental ternately decompound leave* of many leaflets, 
which are often roundish and three-lobed, suggesting 
those of the columbine or maidenhair fern (see cut e un- 
der lea/). The flowers are commonly small, polygamous, 
and panicled, pendulous in T. divicwn and T. minus, and 
reduced to a raceme in T. aininum. They consist chiefly 
of four or five greenish, yellowish, purple, or whitish se- 
pals ; the several or many carpels commonly become com- 
pressed etalked tailless achenes : the anthers are usually 
long and exserted or pendent, giving the inflorescence a 
graceful feathery appearance, and are especially conspicu- 
ous in T. aquilty\folium and T. Jtavum from their yellow 
color. The species are known in general as meadow-rue ; 
3 are natives of England, and 10 or more of the United 
States ; the former T. anemonaides, the rue-anemone, a fa- 
vorite early spring flower of the eastern and central United 
States, is now classed as A nemone thalictroide*, or by some 
as Anemonella ttialictroidts. (See cut under apocarpous.) 
A few dwarf species are used for borders or rock-work, as 
'/'. minus and T. aininum, the latter native of the moun- 
tains of Europe and Asia, as also of the Rocky Mountains, 
and reaching latitude 66 X. About 24 of the taller spe- 
cies are In cultivation, especially T. glaucum of Spain and 
the Austrian '/'. aqutlemfolittm, known as Spanish-tuft and 
feathered or tufted columbine. T. polygamum (formerly 
T. Carnvti), a conspicuous ornament of wet meadows in 
the United States, reaches the height of 4, sometimes 7. 
feet T.flamin is known in England t fen-rue ot maiden- 
hair rue, and as false, monk's, or pour-man's rhubarb. T. 
foliolotum, the yellowroot of the Himalayas, produces tonic 
and aperient roots used iu India in intermittent fevers. 
thalllC (thal'ik), a. [< thallium + -ic.] In 
client., of, pertaining to, or containing thalli- 
um: as, thallic acid. 
thallifonn (thal'i-fdrm), a. [< NL. thallus, q. v., 
+ L. forma, form.] In hot., having the form of 
a thallus. 
thalline (thal'in), a. [< Gr. BaM-ims, of or per- 
taining to a green shoot,< BalMf, a green shoot : 
see thallus.'] In bot., relating to, of the char- 
acter of, or belonging to a thallus Thalline 
exclple. See exeiple. 
thallious (thal'i-us), a. [< thallium + -ous.~] 
Same as that/it: 
thallite (thal'it), n. [< Gr. 6a?Ms, a green 
shoot (see thallus), + -ite 2 .] Same as i/ii<loti-. 
thallium (thal'i-um), n. [NL., so called in allu- 
sion to the green line it gives in the spectrum, 
which led to its discovery ; < Gr. floA/d? , a green 
shoot: see thalhi.i.] Chemical symbol, Tl ; 
atomic weight, 204.2. A rare metal which was 
discovered in the residuum left from the distil- 
lation of selenium by Crookes, in 1861, and was 
thamnium 
lirsl supposed to contain tellurium, but after- 
ward proved, liy the aid of (lie spectroscope, to 
lie new. Thallium as prepared artificially has a bluish- 
white tint and the luster of lead. It is malleable, and so 
soft that It can be scratched with the nnger-iiail. Its 
specific gravity IB 11.8. Thallium Is somewhat widely 
distributed, but never occurs in laige quantities, 'the 
rare mineral called croolcegitt, found In Sweden, is an alloy 
of thallium, selenium, and copper, with a little silver. 
Thallium seems to be present in both linn ami eop|)ei 
pyrites from various localities, and it is from the tine- 
dust from sulphuric-acid works in which pyrites in burned 
that the metal is chiefly obtained. Thallium Is chemical- 
ly classed with the metals of the lead group, hut its reac- 
tions are in certain respects very peculiar and exception- 
al. It has been employed in the manufacture of glass, 
and is said to furnish a glass of extraordinary brilliancy 
and high refractive power. 
thallium-glass (thal'i-um-glas), n. Glass iu 
which thallium is used instead of lead, to give 
density and brilliancy. Compare crystal, 2. 
thallodic (tha-lod'ik), a. [< thnllwi + -<>,!,- 
(-/lid) + -i<:] In but., of or pertaining to the 
thallus ; thalline. 
thallogen (thal'o-jen), n. [< Gr. Oa'/.'/jf, a 
young shoot (see thallus), + -;<rw?f, producing: 
see -yen.~\ In hot., game as titallo)>hyte. 
thallogenous (tha-loj'e-nus), a. [< tliallni/,,1 
+ -oun.] In hot., of or belonging to the thal- 
logens. 
thalloid (thal'oid), a. [< thalluit + -oi>/.] In 
lint., resembling or consisting of a thallus. 
Thalloid hepaticae, hepaticw In which the vegetative 
body does not consist of a leafy axis. 
thallome (thal'om), . [< thallus + -ome(-oma).'] 
In bot., a thallus ; a plant-body undifferentiated 
into members, characteristic of the Thallophyta. 
Thallophyta (tha-lof'i-tft), n. pi. [NL., pi. of 
thallaphytum : see thallophttte.} A subkingdom 
or group of the vegetable kingdom, embracing 
the Myxomycetes, IHatomacete, 8chi:ophyta, Al- 
ga, and Fungi the lower cryptogams, as they 
are still most frequently called. They are planta 
In which the vegetative body usually consists of a thallus, 
which shows no differentiation Into stem, leaf, and root, 
or if there is such differentiation it Is hut rudimentary. 
In regard to complexity of structure, they set out from 
the simplest forms which show no outward distinction of 
parts, and ascend through numberless transitions to more 
and more complex forms of cell and tissue, but even in 
the higher forms they are never differentiated into the 
sharply separated systems of tissue that characterize the 
higher plants. They never have either true vessels or 
woody tissue. In regard to the modes of reproduction, 
they are In as great variety as are the grades of structural 
complexity, ranging from the forms which are propagated 
by simple flsslon to forms that have the sexes as clearly 
differentiated and almost as perfect and complex as are to 
be found In the higher plants. Compare Bryophyta, Pteri- 
dophyta, SpermnphyUt, and Connophyta. 
thallophyte (thal'o-Ht), w. [< NL. thallophy- 
tum, < Gr. 8aA./.6f, a green shoot, + ifivrov, a 
plant.] A plant of the subkingdom Thallophy- 
ta ; one of the lower cryptogams. 
Arboreal plants having structures akin to those of thai- 
lophytes. Pop. Set. Mo., XXXII. 792. 
thallophytic (thal-o-fit'ik), a. [< thallophyte 
+ -M-.J In bot., of or pertaining to the Thal- 
lophyta or thallophytes. 
thallose (thal'os), a. [< tliallus + -one.'] In 
bot.. same as tltalloid. 
thallUB (thal'us), w. [NL., < L. thallus, < Gr. 
toA/Ar, a young shoot or twig,< fldW-nv, be luxu- 
riant, bloom, sprout.] In hot., a vegetative 
body or plant-body undifferentiated into root, 
stem, or leaves; the plant-body characteristic 
of the Thallophyta. Also Ihalamus. See cut 
under applanate Filamentous thallus. Same u 
frutieulfae thallus. Follaceous or frondose thallus, 
in lichens, a flat more or less leaf-like tliallus which 
spreads over the surface of the substratum, but is at- 
tached at only a few points and can be easily separated 
therefrom without much injury. Frutlculose thallus, 
in lichens, a thallus which Is attached to the substratum 
by a narrow base only, from which it grows upward as a 
simple or more or less branched shrub-like body. Strati- 
fied thallus. Sec ttratijied. 
Thalmudt, Thalmudistt, . Obsolete forms of 
Talmud, Talmudist. 
thalweg (G. pron. tal'vech), . [G., < thai, val- 
ley, + tcea, way.] A line upon a topographical 
surface which is a natural watercourse, having 
everywhere the direction of greatest slope, and 
distinguished by having the lines of straight 
horizontal projection which cut it at right an- 
gles on the upper sides of the curves of equal 
elevation to which they are tangent. 
Thammuzt (tham'uz), . Same as Tamniii:. L'. 
Milton, P. L., i. 446, 452. 
thamnium (tham'ni-um), n. [NL., < Gr. 6a/i- 
viov, dim. of ffauvof, a bush, shrub, < 6a>av6f, 
equiv. to Baufiof, crowded, thick, close-set, < 
"aa/ilf, in pi. Qaufec, thick, close-set; cf. Baua, 
often.] In bot., the branched bush-like thal- 
lus of fruticulose lichens. 
