were the human documents he loved best to study.  They wore no masks to conceal their emotions, and he hated masks—­on others.  But above all, they were bone of his bone and flesh of his love, the pledges and hostages he had given to fortune, and they were the children of her to whom he had vowed eternal faith “when their two lives were young.”  But Field’s fondness for other people’s children was like that of an entomologist for bugs—­for purposes of study, dissection, and classification.  He delighted to see the varying shades of emotion chase each other across their little tell-tale faces.  This man, who could not have set his foot on a worm, who shrank from the sight of pain inflicted on any dumb animal, took almost as much delight in making a child cry, that he might study its little face in dismay or fright, as in making it laugh, that he might observe its method of manifesting pleasure.  He read the construction of child-nature in the unreserved expressions of childish emotions as he provoked or evoked them.  Thus he grew to know children as few have known them, and his exceptional gift of writing for and about them was the result of deliberate study rather than of personal sympathy.  That his own children were sometimes a trial to their “devoted mother” and “fond father,” as he described their parents, may be inferred from the facts which were the basis of such bits of confidence between Field and the readers of his “Sharps and Flats” as this: 

An honest old gentleman living on the North Side has two young sons, who, like too many sons of honest gentlemen, are given much to boyish worldliness, such as playing “hookey” and manufacturing yarns to keep themselves from under the maternal slipper.  The other day the two boys started out, ostensibly for school, but as they did not come home to dinner and were not seen by their little sister about the school-grounds, the awful suspicion entered the good mother’s mind that they had again been truant.  Along about dark one of them, the younger, came in blue with cold.

  “Why, Pinny,” said the mother, “where have you been?”

  “Oh, down by the lake, getting warm,” said the youngster.

  “Down by the lake?”

  “Yes; we were cold, and we saw the smoke coming up from the lake, so
  we went down there to get warm.  And,” he continued, in a
  propitiatory tone, “we thought we’d catch some fish for supper.”

  “Fish?” exclaimed the mother.

  “Yes; Melvin’s comin’ with the fish.”

  At this juncture the elder boy walked in triumphantly holding up a
  dried herring tied to the end of a yard or so of twine.

  That night, when the honest old gentleman reached home, the young
  men got a warming without having to go to the steaming lake.

But all of Field’s keen analytical comprehension of child-nature is purified and exalted in his writings by his unalloyed reverence for motherhood.  The child is the theme, but it is almost always for the mother he sings.  Even here, however, he could not always resist the temptation to relieve sentiment with a piece of humor, as in the following clever congratulations to a friend on the birth of a son: