"say, jack, do you have any idea that this thing is going to work?"

"i don't know, bob, the theory is all right, but how it will work out in practice is a cat of another color; one thing is sure, though, and that is if it don't work we are out of the running in the race, for the new boat the jenkins boys have just bought, will run circles round the sprite."

"well, we'll soon know, for it's about ready to test."

this conversation took place one afternoon in the latter part of july in the basement of a house in skowhegan, maine. the room was fitted up as a combined workshop and laboratory, and a single glance would indicate that the two boys were by no means novices, for it contained many expensive and intricate pieces of machinery.4

jack and bob golden, 15 and 17 years old respectively, were sons of a rich manufacturer, who had made a large part of his fortune through his own inventions. mr. golden was an indulgent father and seeing that his inventive genius had descended to his sons, had fitted up a modern machine shop and laboratory for them and had supplied them liberally with money for experiments. he had by no means been disappointed in the results, for although they were but boys, they had already worked out several designs, which had been patented and had proved very successful.

mr. golden was proud of his boys and with good reason. they were large for their age, bob standing 5 feet 10 inches in his stockings and jack being but two inches shorter. they were fine, manly, looking fellows, and their clean-cut open faces told that they were generous to a fault and were boys to be trusted.

the rest of the family consisted of mrs. golden, a small lovable woman, and a daughter edna, 14 years old, who was almost worshipped by her big brothers. altogether they were as happy and jolly a family as one would find in a long journey.

through the center of the town ran the kennebec river, and six miles to the north lay a beautiful sheet of water, five miles long by two wide, known as hayden lake. here the boys kept their motorboat, and as mr. golden had a large cottage on the 5shore of the lake, the family spent the greater part of the summer there. the shores of the lake were dotted with cottages, and probably thirty or more motor boats were owned by the people who made the place their summer home. during each summer many races were held, and proud indeed was the boy or man who secured the blue ribbon given to the winner of the final race held the first week in august.

"i say, jack," shouted bob from the farther side of the room where he was closely watching a piece of electrical apparatus, "shut down the dynamo, will you? i want to look at these cells and see how they are coming. we ought to have about enough in the first one."

"right you are, son!" replied jack as he turned a lever, and as the hum, which had filled the room ceased, he added, "there you are."

bending over a glass tank, which was about 12 inches square by 8 deep, and nearly filled with dilute sulphuric acid, bob disconnected two wires and reaching in his hand, lifted out a cylinder of metal about 6 inches long and 1½ inches thick.

"hurrah," he shouted, "she's almost full. now in about a minute we'll know whether or not we've wasted our time during the last week. have you got those caps all ready and is the motor in trim?"

"sure thing," replied jack. "but say, bob, i'm mighty nervous; suppose it don't work."6

"well," said bob slowly, "it won't be the first time we've had to try again. if there is any trouble i feel sure it's in the caps, for this manganese dioxide was made by the electric current, and if the caps make it decompose into manganese and oxygen, the same amount of electricity will be produced as was used in making it. it's the same principle as the regular storage battery, only we are going to do without the plates and sulphuric acid."

"that's all right," said impatient jack, "but hurry up and hitch it on and let's get the anxiety over with."

while talking, bob had screwed on to each end of the cylinder a metal cap which had attached to its middle an insulated wire. he now laid the cylinder on a table and fastened each of the wires to a terminal of a small, but powerful electric motor.

"all right now, switch her on and let's see her hum."

instantly jack threw over the lever, but, alas for the hopes of the boys, nothing resulted. as they looked at each other keen disappointment was evident on both faces. almost instantly, however, jack grabbed his brother by the arm and almost shouted.

"well, if i'm not the original clumsy claude."

"what is it? tell me quick."

"why, don't you see? i gave you two positive caps instead of a positive and negative."7

bob quickly picked up the cylinder, and a glance told him that his brother was right. quickly unscrewing one cap he replaced it with a similar appearing one, but which was marked — instead of +.

"now we're off again, switch her on," and this time, to their intense delight, no sooner was the switch thrown than the little motor sprang to life, and the armature began to revolve with a whirl which seemed to shout success to the two boys. catching hold of each other's hands they danced about the room fairly shouting their joy.

"for mercy sakes, what is this, a new kind of a war dance?" asked a mild voice, and stopping just at the beginning of a wild yell, the boys saw that their father had entered the room.

"oh, dad," cried both boys, running to him and catching him by the arms. "it works, it works. just see it go."

"well, well, so it does, so it does," said mr. golden eagerly. "boys, i certainly congratulate you; you have done a big thing and if it works as well as it seems to be doing, it will be one of the greatest inventions of the day."

"now," said jack, "we must see how long it will—hold on a minute," and to their amazement he rushed to the back door flung it open and dashed across the yard. he was gone fully five minutes and when he returned was panting for all he was worth.8

"didn't you see him?" he demanded.

"see who?" asked bob.

"why, sure as i live, fred jenkins was looking in that window. he lit out, though, and got away before i could get out."

"what do you suppose he wanted?" asked mr. golden.

"well, i'll tell you, dad," replied bob. "ever since we came down from the lake fred and will jenkins have been trying to find out what we've been doing. you know they almost got us on that new vibrator we invented, owing to our carelessness in leaving it on the table one day when they came in."

"yes," broke in jack, "and they are just mean enough to sneak round and try to steal our new storage cell."

"we've got to be mighty careful this time," continued bob, "and not let one of those caps get into their hands, for the secret of the whole thing is in them, as it is the action of the different metals composing them which starts the manganese dioxide to decomposing and converts its chemical energy into electricity."

"well, come on boys," said mr. golden as soon as bob had finished. "your mother sent me down to tell you to come to supper, and we mustn't be late, as she has company."

"all right," was bob's reply. "just let me connect 9the motor with this clock. you see," he explained, "i have it arranged so that when it stops the clock will stop also and we can tell how long it has run."

several times that evening the boys ran down to the basement to see if the motor was still going, and as it was humming merrily at 10:30, they decided to go to bed and trust to the clock to tell them when it stopped.

early the next morning they rushed to the laboratory before they were half dressed, to find the motor silent and the hands of the clock pointing to 4:35.

"whoop," shouted jack, as he caught sight of the face of the clock, "that's almost twelve hours, just think of it bob. one of those cylinders will run the sprite ten or twelve hours, and it wasn't full either."

"it's sure great," returned bob with no less enthusiasm. "i guess we'll show the jenkins some sailing now."

"that's what we will," agreed jack. "now we must get busy and fill some more of those cylinders."