Expansion of Glass by Heat

Abstract

THE reproduction in your “Physical Notes” (NATURE, vol. xxii. p. 157) of Mr. R. H. Ridout's neat experiment for illustrating the “Expansion of Glass by Heat” (Phil. Mag. for June, 1880), recalls to mind an equally striking method of exhibiting this property of glass to a class of students in physics. Select a straight glass tube 50 or 60 centimetres in length and 1 or 2 centimetres in diameter. Place it transversely in front of a fire, in a horizontal position, properly supported near its two ends on two horizontally-adjusted rods of hard smooth wood of about the same diameter as the tube; the glass tube will gradually roll towards the fire. Now let the supporting rods be transferred to either side of the centre of the tube, so as to support it near its middle; the tube will now gradually roll from the fire.