New-York daily tribune., 1855-08-21

touch not sufbcent 20 destroy the illusion. He
was U dslkeI 90 ets'oroom and the lower edges Of
the Stats were Illuminated by hight placed outside.
He oesrsd also TO call the attention of the Section 70
the importance Of raising the eoscope from philo-
sophic toy 10 a. important in descriptive botany
and zoology. Means may yet be found for taxing
Photograph pic OF freeh orchid ho~ers, rare in
secis &c. from which colored engravings may be
prepared for the stereopcope giving icee of forms
that could not be otherwise acquired but by models
without journey to the tropics.
An engineer present releed the circust ance Of an
isOmotric drawing executed uuder his direction be-
coming perpective when It was taken from the table
ois0rting the design 30 that he could not convioce
hmeelf of its correctness without re-nessuring the
lines. This was not case Of bnocular vision
OS TIE UsT Of Sal Marsh ,Sods for facing ne
steep Slopes Of Parapets and 7erraoes.-By LiEu1
HuNT.-Salt marsh cod has three kinds Of grass-a
sedge, a fox marsh and a black grass The SOD Is
elastic and conpressible hike a sponge. They may
be taken IL inches thick Lieut. II has faced large
amount Of psrapet at Fort Adams, Newport Ordi-
nary sod win not answer for the sleeper work unless
they are laid one upon another Ike wall. para
pet AZ Gloucester, made of salt marsh in 1872 was in
good condition in $50. They used for fences in
ireland, By making two faces Of the sod. They are
cut for forthcaion by plank guides aud cut at the
right beve They must be pressed ioto place,
10 leave 10 vaG ancies They will grow over with
black marsh-grass. They contain stones, and a
cannon ball will throw no dangerous spinters They
wbarves. When we remember that India-rubber was
for long time used only for erssing pencil marks,
and gutta percha for handles, we shall hereafter
study common materials in hopeful spirit.
SOME ADDITIONS 10 the ne1c method Of Astronomical
Observations IN x. Ascension and DecllnqtiOn
and IHdeclia0tiOn. By Prof o. NJ. MITCHELL.
Prof MITCHELL was observing the passage Of the
stars zeta aud 2 over % wires. Averaging the OBJ
sorvs,ions for the night the difference of X. A. was
l.s76" On successive nights they were l.s7O",
l.573", 1.ss6", 1885" l.ss5" 1t was very well while
the errors were in the thousandths of second but
next Dight it out 1897. Here was question to
settle: the cause of the discrepancy. Was it in the
state OF the atmosphere Orthe discrepan nights T1e
% observations Of the same night accorded among
Themselves well the Others Was it owing to
the variation OF personal equation. He tested this by
causing - bright marks to be occulted by nechanism
Mt absolutely equal intervals He recorded them with
uniformity. Was it then owing to the irreguarity of
bis clock . He took another clock and recorded the
beais OF the two clocks side by side but the accessory
CLOCK was not good enough to test the other. lie
thu KS be may find discrepancies in even what are
called good clocks in the thousandths of a second
The Section of Natural History met in Manning
Hall, DIR. Lea in the Chair.
President HITcHcooK exhibited three geological
sections the Valley Of the Connecticut in which
fossil foot-marbs occur and explained the dip strike
and character Of the rocks He made some suppos
tons with regard to the origin of the trap and the dip
Of the sandstone, which drew out some remarks in IL
lustraOn by Mr.. Leslie and Professor Dana. Tne
general impression seemed 10 be that the dip was caused
by lateral pressure, but the riddle of the trap nobody
solved to the satisfaction Of everybody else.
President HITcHcoCK also exhibited series Of foot
marks of an animal which from analogy he had called
a Bairachian. II was web-foOted and the web
tended beyond the toe. Ii was two-legged frog with
feet twice as large elephants. Tbey had in Eu
rope the LabyInthodon who was as large as an OK but
he was mere pigmy compared with this What he
had formerly considered nail he was now convinced
was but prOtuberanee.
Mr. EDWARD DANIELS, recognized by the Legisla-
ure though not by the Governor State Geoogist of
Wisconsin, read a paper on the occurrence of Pro-
boscdon remains in that State and exhibited several
specimens Of bones. They are found principally in
the southwest part Of the State.
Dr. T. C.. HnrARD spoke ON the Physiology of
Sight. lie commenced by alludng TO the faculty
which the eye has Of accommodating itself to differ
eront dstances-of adjusting ts focus. This consists
not in any rounding out Of the for objects
or by any motion of the lens, has been laid down,
but, DIR. Graefe has lately proved, in a lateral
compression of the eyeball, to give it greater
depth. 1t has to be drawn out for objects iust
any other spy glass s. IL ANYBODY will hold this
print AS closely to his eye as possible and make il dis
tinct, he will feel constitution of the eyebal The
scope of sight therefore depends on the refractve
power OF the cOrnoa and the lens and the casual shape
of the bulb. Dlstincness and indisnctncss of vision
depend on certain anatomical organization of the
retna, by which images under certain size
are not perceived; on the power Of the CEN
ter of the retina to distinguish forms more
kcenly than the outer portions; upon whether
the rCtina s in focus not; upon the Y-fomed ar
raneoment of the ber of the lens which often makes
one sec stars when he Goes not bump his head; upon
the width of the pupil the lateral parts of the lens
do not unite rays into exact focus; upon the meet
inc of the axes of the two eyes for when both eyes
are loOl inc al point all objects further nearer
appear double they are not cast on the
Dg places of the two eyes and upon the condition of
the lght arriving which is so serene Alpine hights
that black letters 500 feet high, set up against snow
fields 40 miles distant, might be easily read let
ters onetwentoh of inch in hight at the distance of
eight inches, the angle being the sane: We have
therefore scope of distinct sight equal within all dis
lanccs 10 which the eve 6ccom nodaie itself, for
objects subending the same angle We have one limit
Of most minute VISION namely as near as an object
can be borne and ALSO comfortable distance for long
continued minute vision such reading Psychologists
arc still wondering why we zee things upright wnen
the image on the rotna is upside down. Just as 10
camera-obscura The truth is that we do not con
scously perceive the image; we only perceive by It,
and onr ideas of position are formed from the sense OF
touch The new. born lfant he's no clear vision; at
most II percoivos only light and darkness but II fees
and feeling is its only available sense II hrsi becomes
aware of the position and form OF INNS oI leeilng
And So when we come 10 see, VIC think that sisht
ocs ont and touches the objects which we see, and we
Saw with all the rest Of the world "As far as the eye
"can reach The fiery rings which are seen when
the cs pressed, although form III tle eye Sec
~ he several inches before IT, Persons who are born
bind acquire most perfect knowledge of position by
touch aud on receiving sight, Immediately perceive
things upright. so, standing the head alters no h.
ing in ideas Of up and oowa and astronomers ana
mcrosccpists are not aware that they things
versed We have also consciousness of the absolute
or even the relative size of the image the retiua
since an object looks no larger at the distance OF
r.. ~, A althouph the imaCo IL one