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spiral unwinds itself from left to right, as shown in the figure; the contrary effect takes place when the temperature is lowered. The gold is placed between the two other metals, because it has an expansion intermediate between that of Fig. 163.

lowest temperature to which the instrument has been subjected.

The Thermometrograph.-The spiral thermometer of M. Breguet has been modified by his nephew, of the same name, so as to indicate the hourly state of the temperature. In order to effect this, the index or needle carries a small style or pen full of ink, and below it is a moveable plate, on which are drawn twenty-four equal and equidistant arcs, having the centigrade graduation. At every hour, a clock movement causes the plate to advance by a quantity equal to the interval between two arcs, and at the same time to strike a small blow on the style of the index which then marks a black point on the arc. The number of the arc indicates the hour, and the position of the black point gives the corresponding temperature.

Wedgwood's Pyrometer.-The instruments employed to measure the high temperatures for which the mereurial thermometer could not be employed because of the vaporisation of the liquid and the melting of the glass, are called pyrometers, (from the Greek, fire-measure). There are, however, no good pyrometers. All those which have been hitherto constructed are far from giving the exact measure of temperatures. Wedgwood, whose name has long figured on our best pottery ware, invented a pyrometer founded on the principle that clay contracts by the action of heat. This instrument is com posed of a plate of brass, on which are fixed three bars of the same metal, fig. 165. The length of each is about six inches. The first two, which are at first apart from each other by about half an inch, converge by about a sixth part of that distance between their extremities. The second and third, which follow the former, also converge by the same quantity; so that the whole length of the gauge is about a foot, and the convergence from one end to the other, about one part in seventy-two of the length. Every inch of the length is divided into 20%, which gives 240° on the whole length. In applying Fig. 164.

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silver and that of platinum. By only employing the two latter metals, their difference of expansion would occasion a rupture of the apparatus. This thermometer is graduated by comparing it with the mercurial thermometer as the standard. Rutherford's Thermometer.-In the case of meteorological observations, it is important to know the highest temperature of the day, and the lowest temperature of the night. The common thermometers can only give us this information by continuous observation at every minute of the 24 hours, a thing which is quite impracticable. In order to obviate this difficulty a great number of instruments has been invented; of which the best is that of Rutherford. On a rectangular glass plate, fig. 164, are fixed two thermometers, with their stems

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bent horizontally instead of being placed vertically. The first A is a mercurial thermometer; the second B is an alcohol thermometer. In the stem of the former there is a small iron cylinder at A, which slides freely in the tube, and serves as an index; for when it is put in contact with the extremity of the column of mercury, the instrument being arranged horizontally, if the mercury expands, it pushes the index before it; this index, however, is stopt in its motion as soon as the mercury ceases to expand; but it remains at the same point of the stem when the mercury contracts, for there is no adhesion between this liquid and the iron. The point where the index stops, therefore, marks the highest temperature which has been produced in a given period; in the preceding figure, the index shows about thirty-one degrees.

In the stem of the alcohol thermometer there is placed a small enamel cylinder в which is used as an index. If the temperature is lowered while the cylinder is at the extremity of the liquid column, the latter, when it contracts, draws the cylinder with it by the effect of adhesion, and the index moves on ward to the point where the maximum contraction of the liquid takes place. When the temperature is raised, the alcohol expands and passes between the sides of the tube and the index, without dieplacing the latter. Consequently, the extremity of the index opposite to the bulb indicates the

this instrument, small cylinders of clay, dried in a stove at the temperature of the boiling point, are employed; these cylin ders are made of such a diameter that, at the ordinary temperature, they enter the gauge just at the zero of the scale, as shown in fig. 165. at A. Raised to a high temperature in an oven, the cylinders undergo a contraction, which arises from

Fig. 165.

the commencement of vitrification: when cooled and put into the gauge, they pass the zero point owing to their contraction, and the point where they stop indicates, in degrees of the pyrometer, the temperature of the oven in which they were placed. Wedgwood estimated by approximation that

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the accuracy of this estimate; and the reason is obvious-the cylinders may not in
the zero of his pyrometer corresponded to 10770.5 Fahrenheit, and that each degree
of it was equivalent to 130° Fahrenheit; but other experimenters have questioned
times, and thus their indications are not comparable.
Brogniart's Pyrometer.-M. Brogniart caused to be made, for the ovens of the manu-
all cases be made of the same kind of clay, their construction may vary at different
It consisted of a bar of metal placed in a channel made on a porcelain plate.
factory of Sèvres, a pyrometer very similar to the apparatus represented in fig. 156.
At one end the bar was put in contact with the bottom of the channel; at the other
with a porcelain rod projecting from the oven where the apparatus is placed. This
rod rests on the short arm of an index or needle, of which the long arm moves over a
graduated circular are; so that, in proportion as the metallic bar lengthens by the
to the want of precision in their indications.
rise of its temperature, it pushes against the porcelain rod, and this rod again puts
the index in motion. This pyrometer and Wedgwood's are now scarcely used, owing

"It may, possibly, be thought that the preceding details respecting the construction
filled with quicksilver, could be described, and have its properties explained, in a
and use of thermometers may be elaborately minute, and that an instrument
much more limited space. It should, however, be remembered, that, trifling as this
apparently so trifling as a glass bulb blown on the extremity of a tube, and partially

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LESSONS IN GREEK.-No. XXIX

By JOHN R. BEARD, D.D.

THE AUGMENTS.

The Augment and the Reduplication.

root begins with ev; e.g. evxoμai, I pray, evxoμnv, less often nuxounv; but the Pluperfect is ŋvypai, the ɛ being augmented inton: Evρiokw, I find, discover, in good prose rejects the aug

ment.

Verbs which begin with ă and a following vowel have in the augmented form a instead of n, as aïw (a poetic word), I feel or apprehend, impf. aïov: in those which begin with a, av, ol, and a following vowel, there is no change for the augment, as αηδιζομαι, I am displeased, impf. ἀηδιζομην ; αυαίνω, I dry up,

We must now give fuller particulars respecting the Augment.impf. avaivov; ouw, I steer, impf. ocakizov: also avārior, The Augment is specifically the token of past time. Consequently, it forms a part of the historical tenses,-namely, the Imperfect, the Pluperfect, and the Aorist; but it is retained in no other mood than the indicative. The Perfect, though a principal tense, takes a Reduplication, and to this reduplicated form an Augment is prefixed to form the Pluperfect. The Augment, considered as distinct from the Reduplication, appears in two forms of these, one is called the Sylla bie; the other, the Temporal.

destroy, though no vowel follows the ā, has avāλwσa, avāatdw (in prose gow), I sing, and aïoow (Attic goow), I rush, λωκα, and also ανηλωσα and ανηλωκα. However, the poetic take the augment, as nedov (in prose yoov), niža (Attic yža). Otopar, I think, impf. youny, belongs not here, because the o following the or is not a part of the root.

The Syllabic Augment.

The Syllabic Augment is an e, which in verbs whose root begins with a consonant is prefixed to the stem of the Imperfect and the Aorist, and to the reduplication in the Pluperfect. Thereby is the word augmented (hence the name) by one syllable in the Imperfect and the Aorist, and by two syllables (including the reduplication) in the Pluperfect, e. g. Xvw, Imperfect ε-λυον, Aorist ε-λυσα, Pluperfect ελελύκειν.

When the root begins with p, the p is doubled before receiving the Augment, as ῥιπτω (I throw), Imperfect ερριπτον, Aorist ερριψα, Pluperfect ερριφειν.

In the three verbs, βούλομαι, I will, δύναμαι, I am alle, and peλw, I intend, the Augment with the Attics, the later rather than the earlier writers, is ʼn instead of ; as Impf. ηβουλόμην as well as εβουλόμην, Aorist ηβουλήθην as well as εβουλήθην, Impf. ηδυνάμην as well as εδυνάμην, Aorist ηδυνη θην as well as εδυνηθην (instead of εδυνάσθην), Impf. ημελλον as well as εμελλον : the Aorist is very seldom ημελλησα.

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i, ἱκετεύω, I entreat, impf. ἱκετευον, pf. ἱκετευκα,
pipf. ἱκετεύκειν.

ω, », ὁμιλεω, I accompany, impf. ὡμιλεον, pf. ώμιληκα,

plpf. ώμιληκειν.

ϋ,,, ύβρίζω, Γ insult, impf, ύβριζον, pf. βρικα,
plpf. υβρίκειν.

,,,aipew, I take, impf. yptov, pf. yoŋka, plpf.
ᾑρήκειν.

ην,,, αυλέω, I play on the flute, impf. ηυλεον, pf.
ηυληκα, plpf, ηυλήκειν.

Ψ,,, οικτίζω, I pity, impf. φκτιζον, pf. φκτικα,
pipf. φιτικειν.

In acpew, upeor, the a is lengthened inton, and the is sub-
script; thus, . In avλew, nvcov, the a is simply lengthened
into the n. In ouKTI, KTOV, the o is lengthened into w,
and the is subscript; thus, q.

The Augment is unattended with any change in the verbs
which begin with n, i, u, w, ou, and et, inasmuch as the initial
syllables are already long; as Traoμat, I submit (I am worse,
inferior), pf. ήττημαι, ppt. ήττημην, ἵποω, I press upon, aor.
έπωσα; υπνοω, I put to sleep, aor, ύπνωσα; ωφελέω, 1 benefit,
impi, ωφέλεον, ουτάζω, I wound, impf. ουταζον ; είκω, I yield,
impf, eurov, aor. eiga: Kalw, I liken, guess, forms an excep
tion, which, though but seldom, changes the inton and
underwrites the 4,
thus giving rise to these two forms, ɛikalov,

γκαζον; εικασα, γκασα ; εικασμαι, γκασμαι.
Those verbs also are commonly without the augment whose

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saw, I permit, impf. ewv, aor. Elaσa.
Ow, I accustom, aor. tioa, pf. swea, I am accustomed: eiσa
(from the stem ed), I establish, is poetic; in prose there
are only avaμevog and eraμevos, grounding, instituting.
Moow, I wind, roll, perf. mid. or pass. eiλeyμai.
Xxw, I draw, drag, aor. Eikvoa (stem, iλkv), tiλov (stem iλ),
I took, commonly called the Aorist of aipew, I choose, take.
έπομαι, Ifollow, impf, είπομην.
εργαζομαι, I labour, pf. ειργασμαι.
prw (¿pπvw), I creep, aor. 2. siproV.
ioriaw, I entertain a guest, pf. eioriāka
εχω, I have, aor. 2. είχον.

The ensuing verbs take the syllabic augment instead of the temporal; namely,

ayvμ, I break, a. eaga; perf. 2. ɛāya, I am broken.
άλισκομαι, I am being caught, pf. ἑάλωκα, also ήλωκα, I am
caught (captus sum).

avdavw, I please, impf. lavdavov, pf. ¿āda, aor. 2. ¿ãdov.
oupew, I make water, impf. sovpovv, pf. εovρηка.
woew, I push, impf. Ewlovv; sometimes without augment, as
διωθουντο.
ωνεομαι, I purchase, impf. εωνουμην, also ωνουμην.

The verb opralw, I celebrate a festival, takes the augment in the second syllable, as impf. ἑωρταζον. This happens also in Eikw, I resemble, pf, 2. ɛoɩka, I am like; eoɩke, it is likely; plpf.

εκειν.

έργω, I do, pt. 2. εοργα, plpf. εωργειν
ελπομαι, I hope, pf. 2. εολπα, plpf, εώλπειν } poetic.

The following three verbs have both the syllabic and the temporal augment; the aspirate of the root passes to the augment &:

όραω, I behold, impf. έωρων, pf. έωρακα, έωραμαι.
ανοιγω, I open, impf ανεωγον, a. ανέωξα (inhn, ανοιξαι).
άλισκομαι, I am being caught, a. ἑᾶλων, (infn. ἁλωναι,) also
ήλων.

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The Attic Reduplication.

Several verbs beginning with a or or o repeat in the Perfect and the Pluperfect, before the temporal vowel, the two first letters of the stem : this augmentation is called the Attic Reduplication. The Pluperfect very seldom takes a new augment, as διωρωρυκτο, from ορυσσω (I dig), fut. ορύξω, perf. ορ-ώρυχα, perf. pass. or mid. ορωρυγμαι, pipi, op. and ωρωρυγμήν : in ηκ-ηκόειν the Pluperfect is regular.

The Temporal Augment, as well as the Reduplication, remains in all the moods as well as in the participle. The Attic reduplication affects verbs of two classes: 1. Verbs whose stem-syllable is short by nature, e. g. αρόω, I plough,

ελέγχω, I convince,

ελάω (ελαύνω), I drive, ορύττω, 1 dig,

αρ-ηρόκα, αρ-ηρομαι αρ-ηρόκειν, αρ-ηρομην ελ-ήλεγχα, εληλεγμαι ελ-ηλέγχειν, ελ ηλεγμην ελ-ηλακα, ελ-ηλαμαι ελ-ηλακειν, ελ-ηλαμην ορωρυχα, ορωρυγμαι ορωρυχειν, ορωρυγμην

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συρ-ριπτω,

I cast together,

I arise in, εμβαλλω,

I throw in, συσκευάζω, I pack up,

συν-ερριπτον συνέρριφα

εν εβαλλον εμβέβληκα εν εβεβλήκειν συν-εσκευάζον συν-εσκευακα συνεσκευάκει

The Student should go carefully over this table and account for every change which it presents. I give an example or two. In αποβαλλω, the o of the preposition is dropped before the vowel of εβαλλον, to prevent the hiatus or gaping occasioned by two vowels coming immediately together; but as in βεβληκα the reason ceases, so the o is resumed, and you have αποβεβληκα; yet again αποεβεβλήκειν. In συλλέγω the of the verb has changed the of the preposition into its own sound, namely, A; but when the preposition is not immediately subjected to the form of the A, it resumes its own v as in συνελεγον.

Verbs which are made up of ους, hardly, with difficulty, take the augment of the reduplication, 1. in front, or at the beginning, when the root of the simple verb begins with a consoDant or with η or o ; and 2. in the middle, when the root of the simple verb begins with any other vowel except ŋ and wi

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I am unfortunate, ευς-ωπέω, I blush,

μυς-αρεστεω,

I displease,

ε-ἶυς-ωπουν δε δυς-ωπηκα είδε τις-ωπήκειν δυς-ηρεστούν ευςηρίστηκα δυς-ηρεστήκειν

These two laws are observed by compounds of ev, well; only that such compounds avoid the augment at the begin

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