366 On the component Parts of Light, 
Jake, an impetuous and irresistible discharge of water would be 
the consequence, which, forcing its way through a different tract 
of country from the former stream, must have carried every op- 
posing substance before it, and speedily have formed a new chan- 
nel for itself. But this latter course, from passing along a more 
enlarged plain than formerly, has produced considerable altera- 
tions on the face of the country, which is evidently broken by 
deep hollows that have been washed out by the stream. 
The river in the plain near Comrie has taken various chan- 
nels after the ground was drained by the breaking out of the 
water that anciently covered it; and when it descends below 
Crieff, the whole low land is marked by the numerous courses it 
has pursued at different periods. To trace these windings is not 
an arduous undertaking ; but, excepting in a few instances, a 
particular description might not be generally interesting. The 
deep chasms, however, exhibit some objects of mineralogical 
curiosity, and the steep banks expose a series of alluvial strati+ 
fication, illustrative of the revolutions to which the soil and sur- 
face of mountainous countries are liable. 
Having exhausted too much of your time, on a subject of lit- 
tle importance perhaps to your readers, we have only to observe, 
that in pursuing similar objects of inquiry, sources of rational 
amusement may be developed, which may ultimately lead to the 
acquisition of knowledge and the prosecution of useful science, 
while they must direct the mind to the contemplation of that 
Power whose wisdom has ordered, and whose omniscience has 
regulated, the magnificent and wonderful operations of Nature, 
so constantly under our observation. 
Crieff, Aug. 1, 1817. DICALEDON. , 
LX. On the component Parts of Light, and the Cause of Colour. 
By Cuar.es CARPENTER Bumpass, Esq.* 
I; a beam of solar light be passed through a triangular prism, 
it is divided into several parts of apparently different kinds. On 
one side of the expanded sun-beam or spectrum are rays which 
are invisible, which have been named calorific rays; then are 
seen various coloured rays, in the order of red, orange, yellow, 
green, blue, indigo, and violet; and on the other side ave some 
other invisible rays, which have been called chemical rays, being 
of a different nature from the calorific rays. The rays in the 
centre of the spectrum, Dr. Herschel has found, have the greatest 
power in producing vision; which power gradually diminishes 
towards each side. Neither the calorific nor chemical rays are 
* From his Essay on the Nature of Heat, Light, and Electricity. 
confined 
