"Stop, let us try that experiment again," said he.
They tried it repeatedly, and with the same result, except that the heavy poisonous air below being stirred by the pole, had become somewhat mingled with the pure air above, and the flame was not extinguished quite so suddenly as at first; it burnt more and more dimly as it descended, and then went out.
"I do believe there is something there," said he at last, "and I certainly shall not go down, as I intended. But how am I to get my knife?"
"By using father's magnet, which is a strong one," replied Robert. "Let us go and ask him for it."
On relating the circumstances to Dr. Gordon, he said, "You have made a most fortunate escape, Harold. Had you descended that well, filled as it is with carbonic acid gas, you would have become suddenly sick and faint, and would probably have fallen senseless before you could have called for help. Make it a rule never to descend such a place without first trying the purity of its air, as you did just now."
"But can we not get that bad air out?" asked Harold.
"Yes, by various means, and some of them very easy," replied his uncle. "One is by exploding gunpowder as far down as possible; another is by lowering down and drawing up many times a thickly leaved bush, so as to pump out the foul air, or at least to mix it largely with the pure. But your knife can be obtained without all that trouble. Robert, can you not put him upon a plan?"
"I have already mentioned it, and we have come to ask if you will not let us have your magnet," replied Robert. "But," continued he smilingly, "I do not think that we shall have any need this time for the looking-glass."
Harold looked from one to the other for an explanation, and his uncle said:
"Last year Robert dropped his knife down a well, as you did, and proposed to recover it by means of a strong magnet tied to a string. But the well was deep and very dark, and after fishing a long time in vain, he came to me for help. I made him bring a large looking-glass from the house, and by means of it reflected such a body of sun-light down the well that we could plainly see his knife at the bottom, stowed away in a corner. The magnet was strong enough to bring it safely to the top. You also may try the experiment."