The more learned the examiner, the more kind and indulgent is he to the candidates.
Sainte-Claire Deville, the famous French chemist, had to be declined by the authorities at the Sorbonne as an examiner, because he used to answer his questions himself to save the candidates trouble.
"How do you prepare oxygen?" he would ask. "By heating chlorate of potash, don't you?"
"Yes, sir."
"You place the chlorate of potash in a thin glass flask, don't you?"
"Yes, sir."
"Now a small quantity of manganese bi-oxide, mixed with the chlorate of potash, enables you to obtain the oxygen at a much lower temperature, does it not?"
"Yes, sir."
"Very good—now, another question."
And so forth.