"H'm!" said the doctor; "so that's all you did. Sit down, sir.--Lucas!"

"Yes, sir."

"Do you remember what boys were in the reading-room last night?"

"Yes, sir, but I don't think they were responsible for what happened; it was done by others who came in from outside."

There was a silence.

"I ask once more," said the head-master, "what boys took part in this disturbance? let them stand up!"

Once more young "Rats" alone pleaded guilty.

"Very well, then," continued the doctor sternly; "the whole school will be punished: there will be no half-holiday on Wednesday afternoon, and the reading-room will be closed for a fortnight.--Sit down, Rathson; you are the only boy among the many who must have been connected with this affair--the only one, I say, who has any sense of manliness or honour.

Write me a hundred lines, and bring them to me to-morrow morning."

The prospect of having to work on Wednesday afternoon caused, the boys themselves to take up the doctor's inquiry, and the query, "Who did it?"

became the burning question of the hour.

The riot had evidently been carefully planned beforehand, and the plot arranged in such a manner that those who took part in it might do so without being recognized.

It was impossible to discover who really were the culprits, though the majority of the boys put it down as having been done by "some of 'Thirsty's' lot," and as being a further proof of the latter's well-known animosity towards Allingford, who had, of course, appointed Lucas as keeper of the room.

"Look here!" said Diggory, accosting Fletcher Two in the playground: "what made you tell us to come to the reading-room last night? How did you know there was going to be a row?"

"I didn't," murmured the other warily. "All I knew was that they were going to put 'Rats' in the 'stocks;' I hadn't the faintest idea there was going to be such a fine old rumpus."

"Umph! hadn't you?" muttered Diggory, turning on his heel; "I know better."

CHAPTER XVI.

THE CIPHER LETTER.

The reading-room row, as it was called, had pretty well blown over, when one morning Diggory accosted Jack Vance and Mugford, who were both seated at the latter's desk, sharpening their knives on an oil-stone.

"I say, you fellows, look what I've found." As he spoke, he laid on the desk a slip of paper; it was evidently a sc.r.a.p torn out of some exercise-book, and inscribed upon it were several lines of capital letters, all jumbled together without any apparent object in their arrangement, and, to be more exact, placed as follows:--

NVVGRMGSVTBNDSVMGSVUVOOLD HKZHHLMGLHFKKVIGSVGDLXZM HLUDZGVIZIGHGZMWRMTRMHRW VGSVXFKYLZIWFMWVIGSVHGZRIH.

"Well, what is there funny about that?" asked Jack; "it looks to me as if some one had been practising making capitals."

"Is it a puzzle?" inquired Mugford.

"No, but I'll tell you what I think it is," answered Diggory, sitting down, and speaking in a low, mysterious tone: "it's a letter written in cipher."

"A letter?" repeated Mugford, glancing at the paper. "Why, how could any one read that rubbish--NVVG?"

"Of course they can, if they know the key. Didn't I say it was written in cipher, you duffer? Every letter you see there stands for something different."

"Then why didn't they write the proper letters at once, and have done with it?" grumbled Mugford.

"Because, you prize a.s.s," retorted Diggory, with pardonable asperity, "they didn't want it read."

"Then if they didn't want it read, why did they write it at all?"

exclaimed Mugford triumphantly.

"Oh, shut up! you're cracked, you--"

"Look here," interrupted Jack Vance, "where did you find the thing?"

"Why, you know the window in the box-room that looks out on the 'quad;'

well, there's a little crack under the ledge between the wooden frame and the wall, and this note was stuck in there. I should never have seen it, only I was watching a spider crawling up the wall, and it ran into the hole close to the end of the paper. Some fellows must be using the place as a sort of post-office; don't you remember Fred Acton made one in the wainscotting at The Birches? only these fellows have invented a cipher. Well, I'm going to find it out, and read this note, just for the lark."

"How are you going to do it, though? I don't see it's possible to read a thing like this; you can't tell where one word ends and a fresh one begins."

"There is a way of finding out a cipher," answered Diggory; "it tells you how to do it in that book that we bought when Mug had his things sold by auction at Chatford."

"What, in Poe's tales?" asked Mugford. "Yes; in one of the stories called 'The Gold Bug.' Where is the book?"

"I lent it to Maxton, but I should think he's finished it by this time.

I'll go and see."

"All right," said Diggory, pocketing the slip of paper; "you get it, and then I can show you what I mean. Come on, Jack; let's go out."

The two friends were just rising from the form on which they had been sitting, when they were accosted by Browse, who, strolling up with a pair of dilapidated slippers on his feet, which caused him to walk as though he were skating, inquired in drawling tones, "I say, have either of you kids got a watch-key?"

Jack Vance handed him the required article, which happened to be of the kind which fit all watches.

The Sixth Form "sap" was very short-sighted, and proceeded to wind up his timepiece, holding it close to his spectacles throughout the operation.

"I can't think how it is," he continued, in his sing-song tone, "I'm always losing my key. I've had two new ones already this term.

I always stick them in a place where I think they're sure not to get lost, and then I forget where I put them. Thanks awfully."

"What a queer old codger Browse is!" remarked Diggory, as the big fellow moved away; "no one would ever think he was so clever."

"No," answered Jack Vance. "By-the-bye, did you hear that he had another row with 'Thirsty' last night?"

"No; what about?"

"Oh, the same thing as before. Some fellows were making a beastly row in Thurston's study, and Browse couldn't work, so he threatened if they weren't quiet he'd report them to the doctor. 'Thirsty' came out in an awful wax, and said for two pins he'd knock Browse down; and young Collis, who was standing at the top of the stairs, says he believes he'd have done it if some of the other fellows in the Sixth hadn't come out and interfered."

In the course of the afternoon Diggory secured Mugford's copy of Poe's tales, and (sad to relate) spent a good part of that evening's preparation in trying to unravel the secret of the mysterious missive which he had found in the box-room. So intent was he on solving the problem that, instead of going down to supper with the majority of his companions, he remained seated at his desk, poring over the experiments which he was making according to directions given in the famous story of "The Gold Bug."

"Well, how are you getting on ?" inquired Jack Vance, as the crowd came straggling back from the dining-hall.