The profits of this edition are for the benefits of the Watherlands
Opthalmio Hospital.

To determine tlie acuteness of vision, we measure tke smallest
angle at wkich. objects of known size and known form are distin-
guished.

The value of the angle at which the eye perceives difinite objects depends on the number of
percipient nerve elements which are implicated by the retinal image. The percipient elements,
however, are not distributed in equal number over every part of the retina, but decrease in a
certain order from the centre of the yellow spot to the periphery.

Correctly speaking, the acuteness of vision would be inversely proportioned to the number
of percipient retinal elements which, at the smallest visual angle under which definite forms
are recognized, are implicated by the retinal picture. On this account the determination of
the acuteness of vision, being in inverse ratio to the smallest visual angle, does not afford
us an absolute but only a relative value.

To determine visual angles we measure the extreme distance,
at which objects of definite size (e. g. letters) can be recognized,
or we measure the size of the objects which can be distinguished,
when placed at a definite distance (e. g. one foot).

The angles at which objects appear may be said to stand in inverse proportion to th®
distance amp; in direct proportion to the size of the objects, provided the angles are small; if
however larger angles are concerned, then the size of the object must be assumed to be twice
that of the tangent of half the angle.

Square letters whose limbs liavo a widtli equal to one fifth of
the letters height are generally distinctly visible to a normal eye
at an angle of five minutes.

As objects susceptible o£ mutual comparison, capital letters ot the type known as Egyptian
Paragon have been selected : They are square letters all whose limbs, whether horizontal or
vertical, are of one thickness.

To attain, if possible, more uniform distinctness 1. J, M. Q, W. X, are omitted.

As a standard of vision we adopt clear amp; accurate perception, not uncertain recognition of
objects.

The sizes of our letters, as well as that of the interstices by
which they are separated, accurately measured ofi' upon the
lithographic stone, are as foUows:

The number surmounting the type expresses in Par
distance at which the letters are seen at an angle of 5quot;.

THE DEGEBE OF ACTJTENESS OF VISION (V) IS EXPEESSED BY THE
BELATION OF THE DISTANCE AT WHICH THE LETTER IS ACTUALLY
BEEN (d), TO THAT AT WHICH THE LETTEE IS APPAEENT AT AN
ANGLE OF FIVE MINUTES (D).

If d and D be found equal, amp; No. XX be thus visible at a distance of 20 feet, then
g I 0 _ 1. in other words, there is normal acuteness of vision. Jf, on the contrary,
d be lis than D, and if No. XX is only visible at 10 feet. No. X only at 2 amp; No. VI only at
1 foot, these three eases are thus expressed respectively:

d may sometimes be greater than D, amp; No. XX be thus visible at a greater distance than
20 feet. In this case vision is more acute than the normal average.

Perfect acuteness of vision occurs only witt exact accommo-
dation for tiie given distance. By means of a complete series of
test-types tlie limits of a,ccommodation amp; refraction can tlms be
ascertained.

Since the acuteness of vision, witMn tlie limits of accommo-
dation, is necessarily tlie same for every number, it follows tbat
experiments with letters of different sizes, placed at appropriate
distances, supply a test of the patients sincerity amp; ensure the detection
of attempts on his part to simulate, exaggerate or dissemble.

In astigmatism horizontal and vertical lines cannot be seen
with equal clearness at one and the same time, because in it
the focal distances in the two meridian planes are unequal: In
consequence of this, the squares of a draught board appear
elongated in one direction as grey lines.

The extremes of difference in refraction, in cases of astigmatism, are found in meridian
planes which are perpendicular to each other. The direction of these planes however usually
deviates more or less from the horizontal and vertical.

The size of the pupil is not without its influence upon the
acuteness of vision. If there be little light, vision is more acute
in proportion to the dilatation of the pupil; contraction of the
pupil, on the contrary, increases the acuteness of vision, where
accommodation is imperfect, or where difiuse light comes into play.

The amount of light required for vision is variable amp; depends
especially upon the degree of light to which the eye has been
exposed the moment previously.

Our letters appear nearly alike distinct to normal eyes, whether
they be printed in black upon a white surface, or in white upon
a black surface.

Slender letters are perceived better under the later, whilst thick letters are better seen
under the former conditions.

When the acuteness of vision is lessened, especially if the
diminution results from diffuse light arising from turbidity of
the refractive media, white upon black is better seen than black
upon white.

Coloured letters or wliite letters with coloured illumination
supply tlie means of ascertaining the acuteness of vision for each
colour. In limited light all colours are not equally well per-
ceived by every eye. If the refractive media of the eye have
a certain colour, that colour is seen better than its complemen-
tary colour; in colour-blindness relatively more light is required
to make those colours clearly visible, in regard to which sensi-
bility is impaired.

Eeading must not be identified with the recognition of isolated
letters: in one respect reading is easier, because some letters
can be guessed from their conjunction with others; in another
respect it is more difficult because the letters of words, as they
are usually printed, are very closely arranged.

In experiments in reading, fluency is chiefly to be regarded.
With a contracted or interrupted visual field reading is less
fluent.

II.

III.

IV.
V.

VII.

xvin.

XXVII.
XXXVIII.

The reading-tests appended to our letter-tests are printed in
type as nearly as possible uniform with that selected for the
latter.

As additional reading-tests where with to vary repeated eicaminations amp; to determine the
degree of acnteness with which ordinary print Is seen, we refer to JAEGERS test-types:
The letters in these are not square, are of unequal thickness amp; mutually dissimular both in
dimensions and definition. For these reasons they are not quite comparable with our letter-
tests. If, by measuring the height of the lines, we determine the number, which expresses
the distance at which they appear under an angle of five minutes, then would (JAEGER'S
Schrlftscalen, 2nd edition Vienna, 1859).

quot; quot; quot; ■' » 1.5 „ „ „ „
■' quot; quot;nbsp;.. 8,75 „ „ „

(1) We hope to be able to communicate at a future time additional data concerning this
point. S.



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CLAUDIUS CIVILIS ■WAS A EATAVIAN OP NOBLE RACE, WHO HAD SERVED T-WKNTT-FIVE YKARS Ilf THE
ROMAN ARMIES. HE -WAS A SOLDIER OP FORTUNE, ANIgt; HAD FOUGHT -WHEREVER THE ROMAN EAGLKS
FLEW. AFTER A QUARTKR OF A CENTURY'S SERVICE ME WAS SENT IN CHAINS TO ROME, AND HIS BROTHER
KXECUTED, BOTH FALSELY CHARGED WITH CONSPIRACY. SUCH WERE THE TRIUMPHS ADJUDGED TO BATAVIAN

AUXILIAKIES. HE ESCAPED WITH LIFE, AND WAS DISPOSED TO CONSECRATE WHAT BEMAINED
OP IT TO A NOBLEK CAUSE. CIVIIIS WAS NO BAKBAEIAN. LIKE THE GEKMAN HERO AR-
MINIUS, HE HAD RECEIVED A ROMAN EDUCATION, AND HAD LEARNED THE DEGRADED
CONDITION OF ROME. HE KNEW THE INFAMOUS VICES OF HER RULERS; HE RETAINED

AN nNOONQUEBABLB LOVE rOB LIBERTY AND EOB HIS OWN RACE. DESIRE TO
AVENGE HIS OWN WRONGS WAS MINGLED WITH LOFTIER MOTIVES IN HIS
BREAST. HE KNEW THAT THE SCEPTRE WAS IN THE GIFT OP THE EATAVIAN
SOLDIERY. IT SEEMED A TIME TO STRIKE A BLOW FOR FREEDOM. THE DETAILS

OP THE KEVOLT HAVE BEEN CAEEFULLY PEESEKVED
BY TACITUS, AND FOEM OKE OP HIS GEAWDBST AWD
MOST ELABOEATE PICTtTEES. THE SPECTACLE OP A
BEAVB NATION, INSPIEEB BY THE SOUL OP ONE GEEAT

MAN AND BISING AGAINST AN OVERWHEL-
MING DESPOTISM, WILL ALWAYS SPEAK TO THE
HEABT, PROM GENERATION TO GENERATION.
THE BATTLES, THE SIEGES, THE DEFEATS,

■ : ■■ ■ r.-'^'i'V' v.quot;. -^-. rvr -VW-.'.-,.- • . ■ ■^ Jv.-'
............ . ... ....

THE INDOMITABLE SPIRIT OF CIVILIS,
STILL FLAMING MOST BRIGHTLY WHEN
THE CLOUDS WERE DARKEST AROUND
HIM, HAVE BEEN DESCRIBED BY THE

GREAT HISTORIAN IN HIS MOST
POWERFUL MANNER. THE HIGH-
BORN ROMAN HAS THOUGHT THE
NOBLE BARBARIAN'S PORTRAIT A

SUBJZSCT WORTHY HIS
GEIVriUS. THIS STRUG-
GLE WAS AN UIVSUC-
CESSFUIj OltfE. AFTER

The GalUe tribes fell off, and sued for peace. Even
the Batavians became weary of tte hopeless contest,
while fortune, after much capricious hovering, settled
at last upon the Roman side. Had Civilis been suc-
cessful, he would have been deified j but his misfortunes,
at last, made him odious in spite of his heroism. But
the Batavian was not a man to be crushed, nor hnd
he lived so long in the Roman service to be out-
matched in politics by the barbarous Germans.
He was not to be sacrificed as a peace-offering to
revengeful Rome. Watching from beyond the Rhine
the progress of defection and the decay of national

enthusiasm, he determined to be beforehand with those who were now bis enemies. He
accepted the offer of negotiation from Cerialis. The Roman general was eager to grant a
full pardon, and to re-enlist so brave a soldier iu the service ot the empire. A colloquy was
agreed upon. The bridge across the Nabalia was broken asunder in the middle, and Cerialis
and Civilis met npou the severed sides. The placid stream by which Roman enterprise had
connected the waters of the Rhine with the lake of Plevo, flowed between the imperial

commander and the rebel chieftain. — Here the story abruptly terminates.
The remainder of the Roman's narrative is lost, and upon that broken bridge
the form of the Batavian hero disappears for ever. His name fades from
history: not a syllable is known of his subsequent career; everything is
buried in the profound oblivion which now steals oyer the scene where he
was the most imposing actor. The contest of Civilis with Rome contains a

remarkable foreshadowing of the future conflict with Spain, through
which the Batavian republic, fifteen centuries later, was to be
founded: The characters, the events, the amphibious battles, despe-
rate sieges, slippery alliances, the traits of generosity, audacity,
and cruelty, the generous confidence, the broken faith, seem so
closely to repeat themselves, that History appears to present the

selfsame drama played over and over again, with but
a change of actors and of costume. There is more than
a fanciful resemblance between Civilis and William the
Silent, two heroes of ancient German stock, who had
learned the arts of war and peace in the service of a
foreign and haughty world-empire. Determination,

concentration of purpose, constancy in cala-
mity , elasticity almost preternatural, self-
denial, sonsummate craft in political combi-
nations, personal fortitude, and passionate
patriotism, were the heroic elements in both.
The ambition of each was subordinate to the

cause which he served. Both refused
the crown, although each, perhaps,
contemplated, in the sequel, a Bata-
vian realm of which he would have
been the inevitable chief. Both offe-
red the throne to a Gallic prince.

for Classicus was but the
prototype of Anjou, as
Brinno of Brederode, and
neither was destined, in
this world, to see his sacri-
fices crowned with success.

The characteristics of
the two great races
of the land portrayed
themselves in the Ro-
man and the Spanish
struggle with much

the same colors:
twice a Batavian
republic took its
rank among the
leading powers
of the earth; the

..'-S

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tf'- .

UM-

No. 1 = 0,209 Paris Unes.	No. XI	=	2,304 Paris lines.
„ II = 0,419 „	„ XII	=	2,513
„ III = 0,628 „	„ XV		3,141
„ IV = 0,838 „	„ XX	=	4,189 „
„ V = 1,047 „ „	„ XXX	--	6,283
„ VI = 1,257 „ „	„ XL	=	8,377 .„
„ VII = 1,466 „	„ L	=	10,472 „
„ VIII = 1,675 „	„ LXX	=	14,660
„ IS = 1,885 „	„ C	: -	20,943
„ X = 2,094 „	„ CO	=	41,886

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