How high must a shot-tower be?
A shot-tower must be not less than two hundred feet high, so that the lead may harden while falling.
Why does putty stick to a pane of glass?
Because there is an attraction between the putty and the glass.
What is this attraction called?
It is called Adhesion.
Upon what does adhesion depend?
Adhesion depends upon the attraction which substances have for each other.
Has water any attraction for oil?
No; therefore, there is no adhesion between oil and water.