A multiple by
2 1/4, 3 1/4, &c., gives an intensity equal to one ray only; but a
multiple by 2 1/2, 3 1/2, &c., gives the result of total darkness.
In violet rays similar effects arise when the difference in length
is 0.000157 of an inch; and with all other rays the results are the
same- the difference varying with a uniform increase from the violet
to the red.
Analogous experiments in respect to sound produce analogous results.
*(5) Place a platina crucible over a spirit lamp, and keep it a
red heat; pour in some sulphuric acid, which, though the most volatile
of bodies at a common temperature, will be found to become
completely fixed in a hot crucible, and not a drop evaporates- being
surrounded by an atmosphere of its own, it does not, in fact, touch
the sides. A few drops of water are now introduced, when the acid,
immediately coming in contact with the heated sides of the crucible,
flies off in sulphurous acid vapor, and so rapid is its progress, that
the caloric of the water passes off with it, which falls a lump of ice
to the bottom; by taking advantage of the moment before it is
allowed to remelt, it may be turned out a lump of ice from a red-hot
vessel.
Pages:
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37