LIGHT.

I'J

stances, as they can, under certain circumstances,be in a great measure separated. The most stri-king instance of this was pointed out by Dr. Her-schell.

This philosopher discovered that heat was lessrefrangible than light; for in separating the dif-ferent coloured rays of light by a prism (as we didsome time .ago), he found that the greatest heatwas beyond the spectrum, at a little distancefru*n the red rays, which you may recollect arcthe least refrangible.

EMILY.

I should like to try that experiment.

MRS. B.

It is by no means an easy one: the heat of aray of light, refracted by a prism, is so small, thatit requires a very delicate thermometer to distin-guish the difference of the degree of heat withinand without the spectrum. For in this experi-ment the heat is not totally separated from thelight, each coloured ray retaining acertain portionof it, though the greatest part is not sufficientlyrefracted to fall within the spectrum.

EMILY.

I suppose, then, that those coloured rays whichare the least refrangible, retain the greatest quan-tity of heat ?

They do so.

MRS. B.