The Delaware register, or, Farmers', manufacturers' & mechanics' advocate. [volume] (Wilmington, Del.) 1828-1829, 1829-09-05
LIGHT.

LIGHT
1t is found by optical inquiries that the rays or par
tices of light in passing through transparent substan
ces of certain form, bent to point where they
make an image or picture Of the shining bodies they
come from or of the dark bodies they are reflected
from. Thus, if pair of spectaces be held between
u candle and the wall, they make two images of the
candle upon and if they be held between the win.
dow and sheet OF paper when the is shining they
will make picture the paper of the houses trees
fields, sky and clouds. The eye is found to be compo-
sed ofseveral natural magnifers, which make picture
on membrane at the back of it, and from this men,
brane there goes nerve to the brain, conveying the
impression of the picture, by of which we see
it, Now, white light discovered by Newton to
consist of different coored parts, which are differently
bent in passing through transparent substances so that
the lights of different colors to point at differ
ent distances, and thus create an ndistinct image
This was long found to make telescopes imperfect,
lnsomuch that it became necessary TO make them of
reflectors or mirrors and not of magnifyng glasses
the same difference not being observed to affect their
reflection But another discovery was about fifty years
afterwards made by Mr. Dollond, that by combining
different kinds of glass in compound magnfer, the
difference may be greatly corrected and on this prn-
cple he constructed his telescopes 1t is found too
that the different natural magnfers of the eye are COM
bned upon principle Of the same kind Thirty years
later, third discovery made by Mr. Blair, of the
greatly superior eject winch combinations OF different
liquids have in correcting the mperfection and most
wonderful to think when the eye is examined we find
it consists of different liquids, acting naturally upon
the same principle which thus recently found out
in Optics by many ingenious mechanical and chemical
experiments.
Again, the point to which any magnifer collects the
light is less distant the magnier is smaller
rounder, that small globe of glass or any trans
parent substances makes microscope. And this pro-
perty of light depends upon the of lines, and is
purely of mathematical nature, after we have once
lscertained by experiment, that light is bent in GER
tain way when it passes through transparent bodies
Now birds flying in the air, and meeting with many OBJ
saces branches and leaves oftrees require to have
their eyes sometimes fiat possible for protec-
lion but sometimes round possible, that they may
see the small objects, esand other insects, which they
pursue with the most unerring certainty. This could
only be accomplished by giving them power of sud-
denly changing the form of their eyes. Accordingly.
there is of hard scales placed on the outer coat
of their eye round the place where the light enters
and these scales drawn the muscles or bres bv
which motion is communicated; so that, by acting with
hese MUSCLES the bird press the scaes and squeeze
he natural magnilicr Of the eye into round shape
when it wishes follow insect through the air. and
relax the scales in order to atten the eye again.