46 
A LEARNED DISQUISITION BY LANDSEER. 
ries. This ether, then, is supposed to exist in 
the pores of all bodies, being more dense in 
solid bodies than in empty space, but possess- 
ing less elasticity. An impulse being given 
it, a succession of waves is produced, precisely 
like sonorous vibrations which strike upon the 
retina and cause that membrane to move back- 
wards and forwards, or vibrate, as the undula- 
lory motions of the air, excited by sonorous 
bodies, occasions motions in the membrana 
tympani. These vibrations follow in regular 
succession, and according as they are more 
or less frequent or rapid in succession, the 
sensation of colour is produced. 
The following table exhibits the number of 
vibrations which are distinguishable in a se- 
cond, and the length of a wave : 
Number of vibrations. Length of a wave, 
32 32 
64 16 
128 8 
4096 3 inches. 
8192 li 
The number of vibrations which produce 
the different colours of the sped rum has been 
calculated with wonderful precision : 
Red 458,000,000,000,000, Orange 506, 
Yellow 635, Green 577, Blue 622, Indigo 658, 
Violet 727. The length of a wave is ’0000266 
inch, fiom which we can calculate the vibra- 
tions. 
4’hese numbers are so enormous that one is 
apt to be sceptical as to their accuracy. I’heir 
computation is, however, extremely easy, and 
we are perfectly certain that they form very 
close approximations to the truth. 
By screwing two plates of glass together, 
the rays of light pass through the first, and 
are refracted by the second, and when receiv- 
ed on white paper, exhibit the fits of Newton, 
consisting of alternate light and dark colours, 
A happy idea struck Dr, Ritchie, on the 
morning previous to his lecture, that by a mo- 
dification of this principle, Newton's rings 
might be exhibited. He accordingly screwed 
together two \)lates of glass, divided at their 
margins merely by a layer of gold leaf, direct- 
ing the pressure upon one central point with 
the extremity of the screw, around which were 
beautifully displayed the rings as he had anti- 
cipated. These may be enlarged by additional 
pressure near their circumference. In this 
way these can be measured, and the above 
numbers deduced. Frenelle, by means of in- 
genious apparatus, has been enabled to exhi- 
bit the length of the waves, and measure them 
by means of a microscope. His results were 
the same as those given. Dr. Ritchie consi- 
ders that the experiments of Frenelle prove 
conclusively that light consists of the undu- 
lations of a fluid, interfering with each other 
and producing darkness, 
A further proof in favour of the theory is, 
that when light is passed through a small 
aperture, by reflexion, we have, if we place a 
sheet of paper opposite to the hole, alternations 
of red and dark colours, and M. Arago has 
shewn that light moves more slowly through 
glass than air. M. Colladon, by some very 
interesting experiments at the lake of Geneva, 
has proved that with sound as with light, the 
angle of incidence is equal to the angle of re- 
flexion. Newton objected that if light, like 
sound, consisted of waves, sound ought to 
have a shadow. Now, the fact is that when 
sound passes very rapidly we have a kind of 
shadow of sound, When two tuning forks are 
set differently, we have one sound ascending 
and the other descending, affording a strong 
similarity to the inference of undulations. 
When light is polarized, as by Iceland spar, 
if we cause two portions to act upon the same 
plane, alternations of dark and light colours 
are obtained, shewing interference of waves ; 
but when these portions act at right angles no 
such interference takes place. When light 
passes through a gas, and when we examine 
the spectrum, we observe dark spaces, which 
may be occasioned by one wave interfering 
with another. Light from the sun does not 
possess polarized properties which light from 
a hot iron does, shewing that light is derived 
from the sun’s atmosphere, and not from the 
substance of that luminary, because, in the 
latter case, there would be a gradual diminu- 
tion of its size. A strong argument in favour of 
the undulatory theory is derived from a recent 
experiment of Mr. Faraday, who found, by 
the action of electricity, that as much light 
was given out from a copper wire in the course 
of a few days as could be emitted from the sun 
in a year, Is it possible to suppose that this 
enormous quantity of light existed pent up in 
substantial form in the wire! Dr. Ritchie 
gives his decided negative to such an opinion, 
but is inclined to infer that the light which ena- 
bles us to see exists within ourselves, as the 
heat which warms us is contained within us. 
A LEARNED DISQUISITION ON AN 
ANCIENT RELIC. 
By Mr. Landseer. 
13t/i February, 
M, Landseer lead a very learned disqui- 
sition on a monument, of which a cast was 
brought to this country by Mr. Joseph Beno- 
mi, who has recently published travels in the 
East. The original of this ancient relic exists 
along w'ith nine others on the sea shore near th e 
river Lycus, two hours journey from Bayr- 
root. With the exception of this one of 
which the cast was exhibited to the meeting, 
by permission of Lord Prudhoe, the monu- 
ments are much defaced. 
They were probably seen by Herodotus, for 
he describes similar relics in Ionia. Maun- 
drell saw them in 1767, and describes them 
with great accuracy. Benomi is the only other 
modern traveller who has been fortunate 
enough to fall in with them. He, in the 
most praiseworthy manner, undertook the la- 
bour of making a cast of the most perfect one, 
instead of carrying off the original in the way 
too often practised by eastern visitors. 
It appears to relate to Sesostris or Rameses 
II., who lived, according to Dr. Pritchard, 
1007 years from the commencement of the 
Egyptian era. The principal feature in itis 
the figure of a monarch, with a sceptre in one 
hand, and a dove in the other, of which, howe- 
ver, only the tail remains. The dove was the 
standard of the Assyrians, hence, in the Bible 
itis represented as an oppressor. Over the dove 
