The right merchant is one who has the just average of faculties we call common sense; a man of a strong affinity for facts, who makes up his decision on what he has seen. He is thoroughly persuaded of the truths of arithmetic. There is always a reason, in the man, for his good or bad fortune in making money. Men talk as if there were some magic about this. He knows that all goes on the old road, pound for pound, cent for cent -- for every effect a perfect cause -- and that good luck is another name for tenacity of purpose.