photophone 
One form consists of a thin mirror of silvered mica which 
receives the vibrations from the person speaking, and 
upon which a beam of light falls at the same time. This 
li"ht is reflected to the receiving-point at a distance. 
There it falls upon a concave mirror, and is brought to 
a focus upon a selenium-cell. The variation in the light 
produces a corresponding variation in the electrical re- 
sistance of the selenium, and this reproduces the spoken 
words in a telephone connected with it. 
In the earlier papers describing it [the radiophone] and 
the experiments which led to its invention it is called 
photophone, because at that time the effects were supposed 
to be wholly due to light. Afterwards, in order to avoid 
ambiguity, Bell changed the name to radiophone, and sug- 
gested that, to distinguish between instruments depending 
on the different kinds of radiation, the names photophone, 
thermophone, &c., should be employed. 
Encyc. Brit., XXIII. 130. 
photophonic (fo-to-fon'ik), a. [< plwtojthone 
+ -ic] Pertaining to or produced by the pho- 
tophone. 
photophony (fo'to-fo-ni), . [< photophone + 
-y3] The art or 'practice of using the photo- 
phone. 
pnotophosphorescent (fo-to-fos-fo-res'ent), a. 
[< Gr. 0uf (0ur-), light, + E. phosphorescent.] 
Exhibiting phosphorescence under the action 
of light. See phosphorescence. 
photophysical (fo-to-fiz'i-kal), a. [< Gr. dc 
(0ur-), light, + E. physical.] " Pertaining to the 
physical effect of light: opposed to photochem- 
ical. Athen/eum, No. 3235, p. 562. 
photopolarimeter (fo-to-po-la-rim'e-ter), w. 
[< Gr. <pi>f (<{>OT-), light, '+ E. polarimeter] A 
form of polarimeter devised (1885) by Cornu. 
It has a doubly refracting prism mounted at one end of a 
tube, which at the other has a diaphragm of such size 
that the borders of the two images, polarized at right an- 
gles, just coincide with each other. A nicol prism suit- 
ably mounted is made to revolve until these images have 
the same intensity, when the angular position of its plane 
of vibration gives a ready means of determining the de- 
gree of polarization in the light under examination. 
photo-process (fo'to-pros'es), n. [< Gr. fif 
(<t>ur-), light, + E. process.] Any process or 
method by which is produced, by the agency of 
photography, a matrix in relief or in intaglio 
from which prints can be made in ink ; espe- 
cially, the photographic production of relief- 
plates from which impressions are struck off 
in an ordinary printing-press. It thus includes 
photogravure, but Is especially applicable to such pro- 
cesses of photo-engraving as photolithography and photo- 
zincography. The chief kinds of photo process are differ- 
entiated as follows. Heliotype is the production of a ma- 
trix In gelatin, from which printing is done directly in a 
lithographic press. Photogravure is the production of 
incised or intaglio plates in metal. Photo-engraving is 
(properly) the production of relief-plates of any kind 
suited for printing, together with type, in an ordinary 
printing-press ; though the term is often used to include 
photogravure also. Photo-engraving is particularly ap- 
plicable to the reproduction of pen-drawings ; when used 
for pictures, such as ordinary photographs, it is necessary, 
in order to admit of printing, to employ some such device 
as the formation over the whole surface of the plate of an 
even series of nne lines, or a finely dotted or stippled 
ground. Such plates are called half-tone plates. (See 
half-tone process, under photo -engraving.) Also used at- 
tributively to note a relief-plate, or an impression from 
such a plate, made by photo-process. 
photopsia (fo-top'si-ii), n. [NL.,< Gr. 0<jf (^WT-), 
light, + oi/f, look, sight, < / OJT, see : see optic.] 
The condition of having the sensation as of light 
or of flashes of light without external cause. 
photopsy (fo'top-si), . [= F. photopsie = It. 
fotopsia, < NL. photopsia, q. v.] Same as pho- 
topsia. 
photo-relief (f 6"to-re-lef ' ), a. [< Gr. <t>af (<puT-), 
light, + E. relief.] Noting any process for ob- 
taining by photographic means a matrix in re- 
lief capable of receiving ink and communicat- 
ing impressions, or any block, plate, or print 
produced by such a process. See photography, 
photo-engraving. 
photoscope (fo'to-skop), n. [< Gr. <j>uf (4>"r-), 
light, + momlv, view.] 1. An instrument or 
apparatus for exhibiting photographs. E. H. 
Knight. 2. An instrument consisting of a se- 
lenium-cell, or an arrangement of some other 
substance whose electrical resistance varies 
with the degree of illumination, together with a 
telephone-receiver placed in the same electrical 
circuit, by means of which the varying intensi- 
ties of light may be detected. 
photosculpture (fo't _,__,, ... 
photosculpture ; < Gr. <t>uf (0ur-), light, + E. 
'to-skulp''!^), n. [= F. 
sculpture] Aprocess of sculpturing statuettes, 
medallions, and the like, by the aid of photog- 
raphy. The person whose likeness is to be taken is 
placed in the focus of a number of photographic cameras, 
placed at equal distances from one another, and is thus 
photographed all round. The resulting pictures are pro- 
jected in succession by means of a magic lantern on a 
transparent screen. The operator works behind this 
screen on a piece of modeling-clay, turning it round as he 
proceeds, and copying the images on the screen by means 
of a pantograph which has its reducing-point armed with 
4456 
a molding- or cutting-tool, so that, as the longer arm traces 
every figure on the screen, the shorter one reproduces it in 
the clay. 
photosphere (f'6'to-sfer), . [= F.photogpliere, 
< Gr. <j>af (0ur-), light, + mjialpa, sphere: see 
xphfre.] An envelop of light; specifically, the 
luminous envelop, supposed to consist of in- 
candescent matter, surrounding the sun. Ac- 
cording to Kirchhoff, the sun's photosphere is either solid 
or liquid, and is surrounded by an extensive atmosphere, 
composed of gases and vapors of the substances incan- 
descent in the photosphere. According to the view now 
more generally accepted, the photosphere is a shell of lu- 
minous cloud that is, the solid or liquid particles which 
produce the light are minute, and disseminated through 
the lower strata of the solar atmosphere. 
photospheric (fo-to-sfer'ik), a. [(.photosphere 
+ -ic] Of or pertaining to a photosphere, and 
specifically to the photosphere of the sun. 
phototachometer (f6"t6-ta-kom'e-ter), . [< 
Gr. 0uf (<p"T-), light, + E. tachometer] An in- 
strument for measuring the velocity of light. 
phototachometrical (fo-to-tak-o-met'ri-kal). a. 
[<phototachometr-y + -ic-dl] Pertaining to pho- 
totachometry. 
phototachometry (f6"to-ta-kom'et-ri), n. [< 
Gr. 0<if ((tor-), light, + E. tachometry.] The 
measurement of the velocity of light. 
phototactic (fo-to-tak'tik), a. [< plmtotaxis, 
after tactic.] In "hot., pertaining to, character- 
istic of, or exhibiting phototaxis. 
phototaxis (fo-to-tak'sis), 11. [NL., < Gr. 0<if 
(0wr-), light, + T<if<f, arrangement: see taate] 
In bot., the taking by certain organisms or or- 
tans of a definite position with reference to the 
irection of the incident rays of light, as when 
the zoospores of various plants (Hsematococcus, 
Vlotlirix, etc.) place their long axes parallel to 
the direction of the incident rays. 
photo-telephone (fo-to-tel'e-fon), . [< Gr. 0uf 
(0ur-), light, + E. telephone.] Same as photo- 
phone. 
phototheodqlite (fo"to-the-od'o-lit), n. [< Gr. 
0<if (<j>ar-), light, + E! theodolite.] An instru- 
ment for the performance of triangulation by 
means of photographs. 
phototonic (fo-to-ton'ik), a. [< phototonus + 
-ic] In bot., exhibiting phototonus; charac- 
terized by phototonus. Compare paratonic. 
phototonus (fo-tot'o-nus), . [NL., < Gr. 0wf 
(0cjr-), light, -r-Vwof," tension: see tone.] In bot., 
a term proposed by Sachs for the peculiar con- 
dition m which the protoplasm is capable of 
exhibiting irritability induced in certain plant- 
organs by exposure to light of a certain inten- 
sity. This tonic influence of light is exhibited in the res- 
toration of irritability in organs that have been kept for 
some days in continuous darkness. 
In contrast to the rigidity caused by dark, I have ap- 
plied the term Phototonus to the motile condition result- 
ing from permanent exposure to light. 
Sofhs, Botany (trans. X p. 790. 
phototype (fo'to-tip), . and a. [Cf. F.photo- 
typie; < Gr. <t>uf (</*>r-), light, + ri'Trof, type.] I. 
w. 1. A type or plate for printing, of the same 
nature as an engraved relief-block, produced 
by an application of the photographic proper- 
ties of gelatin sensitized with a bichromate 
(see photo-engraving), or by a combination of 
photographic and etching processes or a com- 
bination of photographic and mechanical pro- 
cesses, as when the lines in intaglio are pro- 
duced by mechanical pressure, these processes 
when combined being commonlv spoken of as 
a single general process; especially, the pro- 
cess known as photozincography. See photo- 
zincography, photolithography, and photoglyphy. 
2. A picture printed from a relief-plate pre- 
pared by a phototype process. 
II. a. Pertaining to or produced by means 
of phototypy : as, a phototype process, plate, or 
print. 
phototype (fo'to-tlp), v. t. ; pret. and pp. photo- 
typed, ppr. prototyping. [< phototype, .] To 
reproduce in phototype or by phototypy. 
phototypic (fo-to-tip'ik), a. [(phototype + 
-ic.] Of, pertaining to, or produced by means 
of phototypy. 
phototypogfaphic (fo-to-tl-po-graf'ik), a. [< 
Gr. ipuf (0ur-), light, -f- ri'Trof, type, + ypifttv, 
write.] Of, pertaining to, or using a photo- 
graphic relief-block adapted for printing in an 
ordinary press: as, the phototypograpMc pro- 
cess of Poitevin. 
phototypy (fo'to-ti-pi), . [< phototype + -yZ] 
The art or process of producing phototypes. 
A combined albumen and asphalt process of phototypy. 
Set. Amer., N. S., LVII. 385. 
photovoltaic (fo"to-vol-ta'ik), a. [< Gr. fif 
(^ur-), light, + E. voltaic.] Relating to an elec- 
Phragmites 
trie current as produced or varied in intensity 
by the action of light, as when the electrical re- 
sistance of selenium is altered by light. 
photoxylography (f6"to-zi-log'ra-fi), . [< Gr. 
0<jf (0wr-), light, + E. xylography.] The pro- 
cess of producing an impression of an object on 
wood 1 >y phot ography and subsequent processes, 
and then printing from the block. 
photozincograph (fo-to-/ing'ko-graf), n. [< Gr. 
(pijf (^r-), light, + E. zincograph.] A plate or 
picture produced by photozincography. Also 
hototnetallograi>h. 
otozincographic (f6-to-/,ing-ko-graf' ik), . 
[< photottnoograph-y + -ic] Of. pertaining to, 
or produced by photozincography. 
photozincography (fo'to-zing-kog'ra-fi), n. [= 
T.photozincographie; asGr. 4>af (((KJT-), light, + 
E. eincography.] A process of photo-engraving 
analogous to photolithography, but having the 
matrix formed on a plate of zinc instead of a 
lithographic stone ; also, photo-etching execut- 
ed on zinc. Alsophotozi>icoti//>i/. 
photozincotype (fo-to-zing'ko-tip), n. [< Gr. 
puf (?*"), light, + E.' zincotype] A plate pre- 
pared for printing by photozincography. 
In place of wood-cuts, photo- zincotypes are very often 
used. Set. Amer., N. S., LV. 49. 
photozincotypy (fo-to-zing'ko-tl-pi), u. [<j>l><>- 
tosincotype + -</3.] Same as photozincography. 
Set. Jmcr.,N. S..LV.94. 
photuria (fo-tu'ri-a), . [NL., < Gr. 0Sf (0t)T-), 
light, + ovpov, urine.] The passage of lumi- 
nous urine. 
Photuris (fo-tu'ris), n. [NL. (Leconte, 1851), 
< Gr. (jtaf (far-), light, + o'vpa, tail.] A genus 
of fireflies of the coleopterous family iMtnpi/ri- 
dee, with nearly 50 species, mainly South Ameri- 
can, three only being found in North America. 
P. pennsylvanica is the common firefly or lightning-bug 
of eastern parts of the United States, about half an inch 
long and of a yellowish color. Its larva is also luminous. 
, j, and cut under lightning-bug. 
Phoxinus (fok-si'nus), n. [NL. (Agassiz, 1837), 
< Gr. 0of<vof, an unknown river-fish.] In ichth., 
a genus of small cyprinoid fishes; the true 
minnows, of small size, tapering form, and 
brilliant colors, the lateral line incomplete if 
present, the dorsal fin behind the ventrals, and 
the mouth without barbels. The type is the com- 
mon European minnow, P. aphya ortei>i; several species 
of the United States are also described. See cut under 
minnow. 
Phractamphibia (frak-tam-fib'i-a), n.pl. [NL., 
< Gr. (ppaKToc., fenced, protected (< ippdoaeiv, fence, 
protect: see phragma), + NL. Amphibia] The 
mailed or loricate amphibians, as labyrintho- 
donts: opposed to Lissamphibia. 
phragma (frag'ma), . ; pi. phragntata (-ma-ta). 
[NL., < Gr. <j>pdy/ia, a fence, partition, < typanaeiv, 
fence in, fence, secure, fortify. Cf. diaphragm, 
etc.] 1 . In bot., a spurious dissepiment or par- 
tition, as that which occurs at the nodes of cer- 
tain calamites, and in various fruits. 2. In 
zoo'l., a partition, septum, dissepiment, or dia- 
phragm. Specifically, in entom. : (a) A transverse parti- 
tion descending from the dorsal surface into the cavity of 
the thorax. (6) The posterior inflexcd border of the pro- 
thorax, concealed by the mesothorax and wing-covers: it 
is found only in those insects in which the prothorax is 
movable. 
phragmacone (frag'ma-kon), . [< Gr. <t>pdy/ia, 
afence, partition (seephragma), + nuvof, cone.] 
The conical, spiral, or otherwise shaped and 
chambered or septate internal skeleton of fossil 
cephalopods, contained in the anterior part of 
the cavity of a hollow hard structure called 
the guard or rostrum. It is homologous with 
the chambered shell of other cephalopods. See 
cut under belemnite. 
phragmacqnic (frag-ma-kon'ik), . [< pJinii/- 
nidcoiie + -ic.] Having the characterof aplirag- 
macone ; relating to a phragmacone. 
phragmata, n. Plural oi phragma. 
Phragmites (frag-mi'tez), . [L., < Gr. <t>pay- 
/tirrn', growing in hedges, < typayfta, a fence : see 
phragma.] A genus of grasses of the tribe fes- 
tticeee and subtribe Artindincee, distinguished 
from its relative Arvndo by spikelets with the 
lowest flower staminate or sterile. There are 3 spe- 
cies, widely scattered throughout all temperate and sub- 
tropical regions. They are the tallest native grasses of the 
northern United States and of Great Britain, where they 
are useful in binding together the earth of river-banks by 
their creeping rootstocks. They are perennials with flat 
leaves and ample panicles, either dense and erect or loose 
and nodding, furnished with conspicuous tufts of long 
silky hairs enveloping the spikelets. P. cmnwunis is the 
marsh-reed of England and the Atlantic United States, 
with the aspect of broom-corn, and hearing ornamental 
plume-like panicles sought for decoration. Also known in 
England as ditch-reed and bennels, and in the western part 
of the United States as cane. 
