£88 
Mr. Macartney's Observations 
situation? as when left uncovered the whole day. The cir- 
cumstance of the scolopendra requiring exposure previous to 
its giving out light, is very unaccountable, as the insect, when 
left to itself, always seeks as much as possible concealment 
during the day ; indeed it is the opinion of some naturalists 
that it is killed by the light of the sun. 
The opinions of Brugnatelli and Carradori are con- 
nected with some general doctrines, respecting the nature of 
light, which I shall not at present venture to discuss. It ap- 
pears to me, that the question is still unresolved, whether 
light has a substantial existence, oris a phenomenon depend- 
ing upon certain operations or conditions of the ordinary forms 
of matter. But the highly ingenious researches of Count 
Rumford, on the laws of what have been called subtile fluids, 
and the extraordinary advances lately made by Mr. Davy, on 
the decomposition of substances, that were hitherto looked 
upon as elementary, give us reason to hope, that future in- 
vestigations may unfold views of the material world, of which 
we can at present have only an indistinct conception ; that 
new modes of analysis may enable us to see things, not 
through a glass darkly,” but more nearly as they are ; and 
that the boundaries of physical and metaphysical science, now 
so far asunder, may be made to approach each other. 
In the present state of our knowledge, our business should 
be, to collect, arrange, and compare phenomena, rather than 
to speculate upon their nature. Nevertheless, I cannot refrain 
from observing, that the circumstances attending the luminous 
appearance of living animals, are much more favourable to 
the supposition of light being a property, than a substance.. 
The quantity of light emitted by an animal in a certain time. 
