But if the ice actually sends rays of caloric to the thermometer, must not the latter fall still lower when the ice is removed?
MRS. B.
No; for the space that the ice occupied, admits rays from all the surrounding bodies to pass through it; and those being of the same temperature as the thermometer, will not affect it, because as much heat now returns to the thermometer as radiates from it.
CAROLINE.
I must confess that you have explained this in so satisfactory a manner, that I cannot help being convinced now that cold has no real claim to the rank of a positive being.
MRS. B.
Before I conclude the subject of radiation I must observe to you that different bodies, (or rather surfaces,) possess the power of radiating caloric in very different degrees.
Some very curious experiments have been made by Mr. Leslie on this subject, and it was for this purpose that he invented the differential thermometer; with its assistance he ascertained that black surfaces radiate most, glass next, and polished surfaces the least of all.
EMILY.
Supposing these surfaces, of course, to be all of the same temperature.