"When you bent the metal piece of which it is made you crowded the metal on the inside of the piece together, and also stretched the metal on the outside of the bend. As the application of heat expands the metal, the contracted particles of the metal on the inside of the piece pushed against each other with greater force than those on the outside, and the bar tried to straighten itself out again."
"I have noticed that if a hose is coiled up and water is forced through under pressure it will straighten out the hose. Is that also the case with the hose?"
"To a certain extent only. Another principle comes into play in that case. Water under pressure acts as a solid, and has a tendency to move along the shortest route or in the most direct way. If, therefore, there is a crook in the pipe the water tries to straighten it out. Steam gauges are made of flattened spirally coiled tubes. One end of the tube is open and the other has an inlet for the steam. The dial finger has a connection with the moving end, and by that means pressure is indicated."
The next morning Harry's temperature was fully one degree higher than the previous day, and the Professor advised that it would be necessary to administer some fever medicine.
"Last week you found several samples of the gentian flower. It is a first-class fever medicine and tonic. Do you think you could distinguish it by its large blue-colored, fringed flowers?"
"I know what you mean; it has one central stalk, with big leaves at the bottom which gradually grow smaller, and in which the stem seems to go up through the flowers."
"That describes it exactly. Get some of the roots, and peel them, then scrape a quantity, so we can give some to Harry."
This is a simple remedy, in the absence of regular fever medicines which were not available to them.
To their great relief the fever abated before morning, and by persistently taking the gentian tonic Harry was soon well again.
This little experience was sufficient notice that in health at least some preparation should be made for illness, which is sure to come to all at most unexpected times. It had also a stimulating effect in more pointedly directing the attention of the boys to the wonders of the vegetable world.