CHAPTER XVI: The March to Derby. 

Two days later when the jailer brought in breakfast to their cell he dropped on the table by the side of the loaf a tiny ball of paper, and then without a word went out and locked the back door. Malcolm put his finger to his lips as Ronald was about to utter an exclamation of joy. 

"One's appetite is not as good here as it was when we were tramping the hills, Ronald; but one looks forward to one's meals; they form a break in the time." 

So saying, he took up one of the lumps of bread and began to ear, securing at the same time the pellet of paper. "We can't be too careful," he said in a whisper. "It is quite possible that they may be able to overhear us." 

"I don't see how," Ronald replied in the same tone; "I see no crack or crevice through which sound could pass." 

"You may not see one," Malcolm said, "but it may exist for all that. One of the boards of the ceiling may be as thin as paper, and anyone listening through could hear every word we say when we speak in our natural voices. The magistrates evidently believe that they have made a valuable capture, and would give anything to prove that their suspicions are correct. Now, I will go and stand at that grated opening and look at this paper, if they are watching us they will see nothing then." 
Where did his cellmate thing they could hear them from?
 One of the boards of the ceiling may be as thin as paper, and anyone listening through could hear every word we say 