THE LIGHT IN THE SKY

"WELL, what do you say, Tom?" asked Ned, in a low voice.

"She's all right as far as I can see, though she may stagger a bit at the take off.""It's a pretty heavy load," agreed the young manager, as he and Tom Swift walked about the big fire-fighting airship Lucifer, which had been rolled outside the hangar."But still I think she'll take it, especially since you've tuned up the motor so it's at least twenty per cent.more powerful than it was.""Perhaps you'd better leave me out," suggested Mr.Baxter, who had been helping the boys."I'm not a feather weight, you know.""I need you with us," said Tom."I want your expert opinion on the effect the new chemicals have on the flames.""Well, I'd like to come," admitted the chemist, "for it will be a valuable experience for me.But I don't want an accident up in the air.""Trust Tom Swift for that!" cried Ned."If he says his aircraft will do the trick, it positively will.""How about leaving me out?" asked Mr.Damon."I'm not an expert in anything, as far as I know." "You are in keeping us cheerful.And we may need you to bless things if there's a slip-up anywhere," laughed Tom, for Mr.Damon had been invited to be one of the party.

"I don't so much mind a slipup," said Mr.Damon, "as I do a slip down.That's where it hurts! However, I'll take a chance with you, Tom Swift.It won't be the first one--and I guess it won't be the last."The work of getting the big airship ready for what was to be a conclusive test of her fire-fighting abilities from the clouds proceeded rapidly.As has been related, Tom had perfected, with the help of Mr.Baxter, a combination of chemicals which was effective in putting out a fire when dropped into the blaze from above.Quantities of this combination had been stored in metal containers which Tom had at first styled "bombs," but which he now called "aerial grenades."The manner of dropping the grenades was, on the whole, similar to the manner in which bombs were dropped from airships during the Great War, but Tom had made several improvements in this plan.

These improvements had to do with the releasing of the bombs, or, in this case, grenades.It is not easy to drop or throw something from a swiftly moving airship so that it will hit an object on the ground.During the war aviators had to train for some time before becoming even approximately accurate.

Tom Swift decided that to leave this matter to chance or to the eye of the occupant of an airship was too indefinite.Accordingly he invented a machine, something like a range-finder for big guns.With this it was a comparatively easy matter to drop a grenade at almost any designated place.

To accomplish this it was necessary to take into consideration the speed of the airship, its height above the ground, the velocity of the wind, the weight of the grenades, and other things of this sort.But by an intricate mathematical process Tom solved the problem, so that it was only necessary to set certain pointers and levers along a slide rule in the cockpit of the craft.Then when the releasing catch was pressed, the grenades would drop down just about where they were most needed.