Currents in Boiling Water.
Fill a large glass tube with water, and throw into it a few particles of bruised amber or shreds of litmus; then hold the tube by a handle for the purpose, upright in the flame of a lamp, and as the water becomes warm it will be seen that currents, carrying with them the pieces of amber will begin to ascend in the center, and to descend towards the circumference of the tube. These currents will soon become rapid in their motions, and continue till the water boils.
Hot Water Lighter than Cold.
Pour into a glass tube, about ten inches long and one inch in diameter, a little water colored with pink or other dye; then fill it up gradually and carefully with colorless water, so as not to mix them; apply heat at the bottom of the tube, and the colored water will ascend and be diffused throughout the whole.
Expansion of Water by Cold.
All fluids except water diminish in bulk till they freeze. Thus, fill a large thermometer tube with water, say of the temperature of eighty degrees, and then plunge the bulb into pounded ice and salt, or any other freezing mixture; the water will go on shrinking in the tube till it has attained the temperature of about forty degrees, and then, instead of continuing to contract till it freezes, it will be seen slowly to expand, and consequently to rise in the tube until it congeals.
In this case the expansion below forty degrees and above forty degrees seem to be equal, so that the water will be of the same bulk at thirty-two degrees as at forty-eight degrees, that is, at eight degrees above or below forty degrees.