"No, I didn't do that," Tom said, with a laugh."And I only have a theory as to the cause of the blaze.But suppose we go down and take a look.There's a good field around this grove, and we can get a fine take off.I'll have to go back to Shopton anyhow, to get some more of the chemical."So the aeroplane made a landing, and then the mystery was explained.The dead oak, to which some of its last year's foliage still clung, was the abiding place of thousands of crows that had built their nests in it.There were hundreds of the big nests, made of dried sticks, mostly, and these made an ideal fuel for the fire.
"But where are the crows, and what started the fire?" asked Ned.
"I fancy the birds flew away as soon as they saw their homes on fire," said Tom."Or they may not have been at home.Flocks of crows often go to some distant feeding ground for the day, returning at night.I fancy that is what happened here.
"As for the cause of the blaze, I believe it was set by some mischievous boys, who saw a good chance to have some fun without thought of doing any real damage.For the dead tree was of no value, and I imagine the farmers would be glad to see the flock of crows dispersed.Some boys probably climbed up and set fire to one of the nests, and then, when they saw the whole lot going, they became frightened and ran away."And Tom's theory was, eventually, proved to be true.Some lads, wandering afield, had set fire to the crows' nests and then, frightened as they saw a bigger blaze than they intended, ran away.
Tom and Ned did not remain to see what the returning crows might think about the destruction of their homes, provided they saw fit to return, but, starting the aeroplane, were again on their way.
Tom had lingered long enough to make sure that his latest combination of chemicals had been just what was needed.He felt sure that by using a larger quantity, no fire, however fierce, could continue to blaze.
"But I want to give it a good trial, Ned, as we did from the tower," said Tom."Though I don't believe there'll be a fizzle this time."It did not take long for Tom to secure another supply of the new chemical.He then went with it to the firm in Newmarket that was making his containers, or "bombs" as he called them.
On his return he consulted with Mr.Baxter as to the ingredients of the fluid that had put out the blaze in the tree.
"I believe you have at last hit on the right combination," said the chemist."You are on the road to success, Tom.I wish I could say the same of myself.""Perhaps your formulae may come back to you as suddenly as they disappeared, or as quickly as I discovered that I had the right thing to put out the fire," said Tom hopefully.
Busy days followed for the young inventor.Now that he was convinced he had at last evolved the right mixture of chemicals, he prepared to make a test on a larger scale than merely a blazing tree.
"I'll try it with a fire in the pit," he said to his chum.
Preparations were made, and the day before Tom was to carry out his plans he received a letter.
"What's the matter? Bad news?" asked Ned, as he saw his friend's face change after reading the epistle.
"Nothing much.Only Mary is going away, and I had expected her to be at the test," Tom answered.
"Going away?" echoed Ned.For long?"
"Oh, no, only for a couple of weeks.She is going to visit an uncle and aunt in Newmarket, or just outside of that city.Another uncle, Barton Keith, has offices in the Landmark Building, I believe.""Landmark Building," murmured Ned."Isn't that where Field and Melling hang out?""Yes.But don't mention Mary's uncle in connection with them," laughed Tom."He wouldn't like it.""I should say not!"
Ned well remembered Mary's uncle, who had been associated with Tom in recovering the treasure in the undersea search.
"Well, if she can't be here, she can't," said Tom, as philosophically as possible."I'd better run over and bid her goodbye."This Tom did, though Ned noticed that his chum acted as though lonesome on his return.
"But when he gets to work testing his new chemical he'll be all right," decided Ned.
