was considered valuable in matters electrical, as those of you, who have read the previous books in this series, well know.

The little group in the machine shop was soon deep in the discussion of ohms, amperes, volts and currents, and, for a time, Tom almost forgot the message calling him to Philadelphia.

Taking advantage of the momentary lull in the activities of the young inventor, I will tell my readers something about him, so that those who have no previous introduction to him may feel that he is a friend.

Tom Swift lived with his father, Barton Swift, a widower, in the village of Shopton, New York. There was also in the household Mrs. Baggert, the aged housekeeper, who looked after Tom almost like a mother. Garret Jackson, an engineer and general helper, also lived with the Swifts.

Eradicate Sampson might also be called a retainer of the family, for though the aged colored man and his mule Boomerang did odd work about the village, they were more often employed by Tom and his father than by any one else. Eradicate was so called because, as he said, he "eradicated" the dirt. He did whitewashing, made gardens, and did anything else that was needed. Boomerang was thus named by his owner, because, as Eradicate said, "yo' nebber know jest what dat mule am goin' t' do next. He may go forward or he may go backward, jest laik them Australian boomerangs."

There was another valued friend of the family, Wakefield Damon by name, to whom the reader will be introduced in due course. And then there was Mary Nestor, about whom I prefer to let Tom tell you himself, for he might be jealous if I talked too much about her.

In the first book of this series, called "Tom Swift and His Motor-Cycle," there was told how he became possessed of the machine, after it had nearly killed Mr. Damon, who was learning to ride it. Mr. Damon, who had a habit of "blessing" everything from his collar button to his shoe laces, did not "bless" the motor-cycle after it tried to climb a tree with him; and he sold it to Tom very cheaply. Tom repaired it, invented some new attachments for it, and had a number of adventures on it. Not the least of these was trailing after a gang of scoundrels who tried to get possession of a valuable patent model belonging to Mr. Swift.

Our second book, called "Tom Swift and His Motor-Boat," related some exciting times following the acquisition by the young inventor of a speedy craft which the thieves of the patent model had stolen. In the boat Tom raced with Andy Foger, a town bully, and beat him. Tom also took out on pleasure trips his chum, Ned Newton, who worked in a Shopton bank, and the two had fine times together. Need I also say that Mary Nestor also had trips in the motor-boat? Besides some other stirring adventures in his speedy craft Tom rescued, from a burning balloon that fell into the lake, the aeronaut, John Sharp. Later Mr. Sharp and Tom built an airship, called the Red Cloud, in which they had some strenuous times.

Their adventures in this craft of the air form the basis for the third book of the series, entitled "Tom Swift and His Airship." In the Red Cloud, Tom and his friends, including Mr. Damon, started to make a record flight. They left Shopton the night when the bank vault was blown open, and seventy-five thousand dollars stolen.

Because of evidence given by Andy Foger, and his father, suspicion pointed to Tom and his friends as the robbers, and they were pursued. But they turned the tables by capturing the real burglars, and defeating the mean plans of the Fogers.

Not satisfied with having mastered the air Tom and his father turned their attention to the water. Mr. Swift perfected a new type of craft, and in the fourth book of the series, called "Tom Swift and His Submarine," you may read how he went after a sunken treasure. The party had many adventures, and were in no little danger from their enemies before they reached the wreck with its store of gold.

The fifth book of the series, named "Tom Swift and His Electrical Runabout," told how Tom built the speediest car on the road, and won a prize with it, and also saved a bank from ruin.

Tom had to struggle against odds, not only in his inventive work, but because of the meanness of jealous enemies, including Andy Foger, who seemed to bear our hero a grudge of long standing. Even though Tom had, more than once, thrashed Andy well, the bully was always seeking a chance to play some mean trick on the young inventor. Sometimes he succeeded, but more often the tables were effectually turned.

It was now some time since Tom had won the prize in his electric car and, in the meanwhile he had built himself a smaller airship, or, rather, monoplane, named the Butterfly. In it he made several successful trips about the country, and gave exhibitions at numerous aviation meets; once winning a valuable prize for an altitude flight. In one trip he had met with a slight accident, and the monoplane had only just been repaired after this when he received the message summoning him to Philadelphia.

"Well, Tom," remarked his father that afternoon, "if you are going to the Quaker City, to see Mr. Fenwick to-morrow, you'd better be getting ready. Have you wired him that you will come?"

"No, I haven't, dad," was the reply. "I'll get a message ready at once, and when Eradicate comes back I'll have him take it to the telegraph office."

"I wouldn't do that, Tom."

"Do what?"

"Trust it to Eradicate. He means all right, but there's no telling when that mule of his may lie down in the road, and go to sleep. Then your message won't get off, and Mr. Fenwick may be anxiously waiting for it. I wouldn't like to offend him, for, though he and I have not met in some years, yet I would be glad if you could do him a favor. Why not take the message yourself?"

"Guess I will, dad. I'll run over to Mansburg in my electric car, and send the message from there. It will go quicker, and, besides, I want to get some piano wire to strengthen the wings of my monoplane."

"All right, Tom, and when you telegraph to Mr. Fenwick, give him my regards, and say that I hope his airship will be a success. So it's an electric one, eh? I wonder how it works? But you can tell me when you come back."

"I will, dad. Mr. Jackson, will you help me charge the batteries of my car? I think they need replenishing. Then I'll get right along to Mansburg."

Mansburg was a good-sized city some miles from the village of Shopton, and Tom and his father had frequent business there.

The young inventor and the engineer soon had the electric car in readiness for a swift run, for the charging of the batteries could be done in much less than the time usual for such an operation, owing to a new system perfected by Tom. The latter was soon speeding along the road, wondering what sort of an airship Mr. Fenwick would prove to have, and whether or not it could be made to fly.

"It's easy enough to build an airship," mused Tom, "but the difficulty is to get them off the ground, and keep them there." He knew, for there had been several failures with his monoplane before it rose like a bird and sailed over the tree-tops.

The lad was just entering the town, and had turned around a corner, twisting about to pass a milk wagon, when he suddenly saw, darting out directly in the path of his car, a young lady.

"Look out!" yelled Tom, ringing his electric gong, at the same time shutting off the current, and jamming on the powerful brakes.

There was a momentary scream of terror from the girl, and then, as she looked at Tom, she exclaimed:

"Why, Tom Swift! What are you trying to do? Run me down?"

"Mary--Miss Nestor!" ejaculated our hero, in some confusion.

He had brought his car to a stop, and had thrown open the door, alighting on the crossing, while a little knot of curious people gathered about.

"I didn't see you," went on the lad. "I came from behind the milk wagon, and--"

"It was my fault," Miss Nestor hastened to add. "I, too,