there was once a poor woodcutter who toiled from early morning till late night. when at last he had laid by some money he said to his boy, "you are my only child, i will spend the money which i have earned with the sweat of my brow on your education; if you learn some honest trade you can support me in my old age, when my limbs have grown stiff and i am obliged to stay at home." then the boy went to a high school and learned diligently so that his masters praised him, and he remained there a long time. when he had worked through two classes, but was still not yet perfect in everything, the little pittance which the father had earned was all spent, and the boy was obliged to return home to him. "ah," said the father, sorrowfully, "i can give you no more, and in these hard times i cannot earn a farthing more than will suffice for our daily bread." "dear father," answered the son, "don’t trouble yourself about it, if it is god’s will, it will turn to my advantage i shall soon accustom myself to it." when the father wanted to go into the forest to earn money by helping to pile and stack wood and also chop it, the son said, "i will go with you and help you." "nay, my son," said the father, "that would be hard for you; you are not accustomed to rough work, and will not be able to bear it, besides i have only one axe and no money left wherewith to buy another." "just go to the neighbour," answered the son, "he will lend you his axe until i have earned one for myself." the father then borrowed an axe of the neighbour, and next morning at break of day they went out into the forest together. the son helped his father and was quite merry and brisk about it. but when the sun was right over their heads, the father said, "we will rest, and have our dinner, and then we shall work as well again." the son took his bread in his hands, and said, "just you rest, father, i am not tired; i will walk up and down a little in the forest, and look for birds’ nests." "oh, you fool," said the father, "why should you want to run about there? afterwards you will be tired, and no longer able to raise your arm; stay here, and sit down beside me." the son, however, went into the forest, ate his bread, was very merry and peered in among the green branches to see if he could discover a bird’s nest anywhere. so he went up and down to see if he could find a bird’s nest until at last he came to a great dangerous-looking oak, which certainly was already many hundred years old, and which five men could not have spanned. he stood still and looked at it, and thought, "many a bird must have built its nest in that." then all at once it seemed to him that he heard a voice. he listened and became aware that someone was crying in a very smothered voice, "let me out, let me out!" he looked around, but could discover nothing; nevertheless, he fancied that the voice came out of the ground. then he cried, "where art thou?" the voice answered, "i am down here amongst the roots of the oak-tree. let me out! let me out!" the scholar began to loosen the earth under the tree, and search among the roots, until at last he found a glass bottle in a little hollow. he lifted it up and held it against the light, and then saw a creature shaped like a frog, springing up and down in it. "let me out! let me out!" it cried anew, and the scholar thinking no evil, drew the cork out of the bottle. immediately a spirit ascended from it, and began to grow, and grew so fast that in a very few moments he stood before the scholar, a terrible fellow as big as half the tree by which he was standing. "knowest thou," he cried in an awful voice, "what thy wages are for having let me out?" "no," replied the scholar fearlessly, "how should i know that?" "then i will tell thee," cried the spirit; "i must strangle thee for it." "thou shouldst have told me that sooner," said the scholar, "for i should then have left thee shut up, but my head shall stand fast for all thou canst do; more persons than one must be consulted about that." "more persons here, more persons there," said the spirit. "thou shalt have the wages thou hast earned. dost thou think that i was shut up there for such a long time as a favour. no, it was a punishment for me. i am the mighty mercurius. whoso releases me, him must i strangle." "softly," answered the scholar, "not so fast. i must first know that thou really wert shut up in that little bottle, and that thou art the right spirit. if, indeed, thou canst get in again, i will believe and then thou mayst do as thou wilt with me." the spirit said haughtily, "that is a very trifling feat," drew himself together, and made himself as small and slender as he had been at first, so that he crept through the same opening, and right through the neck of the bottle in again. scarcely was he within than the scholar thrust the cork he had drawn back into the bottle, and threw it among the roots of the oak into its old place, and the spirit was betrayed.