nedham was right. it was some time after midnight before the big generators were in condition to operate again. for hours the men toiled to get every vestige of the gritty substance out of the machines. mr. ryder went at the task with the rest, and jack, unwilling to remain idle, rolled up his sleeves and seized a piece of cotton waste also. with the steel jacket removed, an excellent opportunity was afforded the lad for a better acquaintance with the mechanism of a water turbine generator, and as he worked beside mr. ryder, the engineer briefly explained the details.
“this is not really a generator that we are working on, jack,” said mr. ryder, “because a generator is supposed to create energy. this does not do that. the real energy is in[89] the water that turns the turbine, and this machine merely converts that energy into electric current, so you see the word ‘generator’ is a misnomer in this case. it is the same in a steam plant. steam furnishes energy which is converted into electricity by the so-called generators. in fact, man-made electricity is nothing more or less than some other kind of energy in a new and more useful form. i guess you follow me.”
“i understand all right,” said jack, “for it is very simple, though i must confess i had never considered electricity in that way before.”
“the energy here comes from the water that plunges over the dam we built across the river about a mile back in the mountains. the dam is sixty-odd feet high and the water that is stored up behind it is carried down to the plant here through a very large flume. the flume is built at the same level as the dam and brings the water around the mountain to the north of the plant and into the big forebay or reservoir just back of the station.
“the water in the forebay is kept at about[90] the same height as the dam also, so it can get a sixty-foot direct drop to the turbines here in the building. the stream rushes down through the large penstocks, or feeders, and strikes against the mass of concaved blades on the waterwheel or turbine. the blades are set across the drum of the wheel and at a slight angle, thus giving the turbine the full benefit of the force of the water striking against them as well as the suction of the water after it leaves the blades. this is known as the reaction type of turbine and is only used in plants where the fall of water is less than 100 feet. there is another type of waterwheel on which buckets take the place of blades. this is known as the impact type and is driven entirely by the pelting of the water against the bottom of each cup. this wheel is used chiefly where the fall of water is more than 100 feet.
“the armature of the generator is also mounted on the shaft or axle of the turbine. the armature, you know, is composed of coils of wire wound very close together on an iron frame, or spider. since the turbine whirls around very fast the armature is bound to[91] turn at the same rate of speed. now, the armature is surrounded by electrically excited magnets, which are the positive and negative poles of the generator. and as the coils of wire on the armature rush past the magnets the attraction or lines of force between the poles are cut abruptly and immediately electricity is created. by means of those brass collecting rings which you see on the armature the coils are connected to the transmission lines and the electricity flows through them to the lights in mexico city.”
mr. ryder’s description of the hydro-electric plant was so simple and so easily understood that jack was able to follow the entire process of converting water power into electrical energy. the conversation had also helped to lighten the rather disagreeable task of cleaning the generator and it was midnight almost before they realized it.
at this hour mr. ryder gave up all hope of using the generator that night, for, as he explained to jack, the lights were fast being put out in the houses and stores of mexico city, thus cutting down the load on the power plant[92] to a point where the supply could be easily furnished by the remaining four machines. that being the case, he suggested they quit work and leave the task entirely to the peons and other workmen under nedham. jack’s arms were black to the elbow with dirty oil when he finally tossed his piece of waste away, and mr. ryder’s condition was little better.
“come on, we’ll wash up a bit and start for the cottage; i am rather tired and i fancy you are too.”
together they proceeded to the washroom and a few moments later left the station building and started up the short dusty street that led between the two rows of cottages. the searchlight was still playing from the roof and here and there a lonesome sentinel could be seen silhouetted against the skyline. otherwise the little community was quite lifeless.
mr. ryder’s cottage was at the very end of the short street. it was a one-story affair but somewhat more prepossessing in appearance than the rest of the dwellings. the engineer lived there entirely alone save for tom why, his aged chinese cook. in fact,[93] each american at the plant had a separate cottage, which was usually taken care of by some old indian woman. there were only two white women in the village. one was the wife of allen lyman and the other was mrs. harriet clifford, the wife of a young american foreman in the plant-maintenance department.
mr. ryder’s cottage was no better furnished than any of the rest. the main room, which was living room, dining room, library and study all in one, was equipped with several heavy wooden chairs, a square table and a flat desk littered with old magazines and papers. the remaining three rooms boasted small iron beds and washstands. just in the rear of the cottage was a little house in which tom why and his american cookstove were quartered. tom was acknowledged to be the best cook in the village, excepting, of course, the two american women.
though it was very late, tom was up and waiting for the engineer. he had prepared a rather substantial midnight luncheon and when jack caught the odor of steaming coffee he suddenly realized that he was extremely[94] hungry. neither he nor mr. ryder had tasted food since their dinner at the american hotel in mexico city, and they were both ready to do justice to tom’s tempting spread. between mouthfuls, however, they did find time to talk over the recent trouble at the plant.
“i must get at the bottom of this and find out who the rebel sympathizers are. of course they are among the peon laborers, at least i think so, for none of the white employees have the slightest interest in zapata and his gang of cutthroats, as far as i know. still, the way the trouble makers have tampered with the big switches and other dangerous machinery that most of the peons are afraid of, makes me believe sometimes that the culprits are white men or natives who know a little more about electricity than the peons.”
“i should think then, that you would try and find out whether you are dealing with peons or mexicans of another variety,” said jack.
“find out!” demanded the engineer sharply. “do you think i have been sitting with my hands folded all this time? i’ve had the place watched. i’ve done everything i could to discover[95] who is up to this crooked work. you see, after two in the morning things slacken down at the plant. there isn’t much of a load to be carried, only the street lighting in mexico city, and one or two generators are enough to take care of that. at that time most of the men leave the plant. there is only the night operator and two or three watchmen in different parts of the building, and they are not always as alert as they might be. well, between two o’clock and the time the day force comes on at six o’clock in the morning, the meddlers get in their best work. the day men usually discover the trouble, though in a case like to-night, when one of the big machines have been tampered with, the disturbance isn’t noticed until the operator tries to start up at nightfall.
“we’ve watched everything and everybody, but when we are in one place trouble turns up in an entirely different part of the plant. the thing that worries me the most about the whole business is that some night after the meddlers have been at work the rebels out there in the mountains might take it in their heads to attack.[96] suppose the searchlight generator was crippled. in that case we’d have a serious time, wouldn’t we? indeed, i would like to find out whom we are dealing with. but how can i?”
“well,” said jack after a moment’s reflection, “at least we can learn whether we are dealing with peons or white men. here’s a suggestion. why not sprinkle a little powder or dust around the machines, switchboard and other apparatus likely to be tampered with? sprinkle it at two o’clock every morning and sweep it up again at six. in the meantime if any one has tampered with these contrivances they are bound to leave footprints. if the prints show naked feet we’ll know it is one of the peons, and if we find the trouble maker wears shoes then we’ll know it is a white man.”
“by jove, that’s a corking idea,” said mr. ryder enthusiastically; “we’ll do it. we’ll sprinkle cement dust on the floor. let’s try it out to-night and keep it up religiously until we get an imprint of the villain’s feet. we’ll saunter over to the plant after those workmen clear out, which i judge will be about three[97] o’clock; meanwhile, if you care to, you can snatch an hour’s sleep.”
to jack sleep sounded particularly good and as soon as mr. ryder pointed out his room he tumbled into it without even removing his shoes. but it seemed to him however that he had only closed his eyes when he felt the engineer’s hand upon his forehead.
“it’s after three o’clock,” said mr. ryder, “and the workmen have all left the plant. what do you say to setting our trap now?”
jack was on his feet in an instant, for he was as eager as the engineer to see how his plan would work out. first they visited a tool shed where they secured a bucket, then mr. ryder ripped open a bag of cement with his jack knife and by the light of an electric pocket flash lamp supplied himself with a pail of the fine gray powder.
as they passed the front of the plant they could see nedham in his office working over some papers. they continued on around the corner of the building where mr. ryder opened a large door that let them in on the generator floor. two of the big machines were running,[98] but there was not a soul in sight. through the glass front of the control room, high up among the girders, they could see lyman watching the switchboard.
“is there any wonder that the rebel sympathizers can tamper with the machines?” said mr. ryder; “there isn’t a watchman in sight, and lyman would not be likely to see us down here unless he made a point of looking out of the window, which is not necessary, for he can see how the machines are running by looking at the indicators on his board. nedham is in his office and the only other man on duty is the engineer and he is probably in his office watching for signals from lyman. there should be a watchman here on the floor, but i guess when no one is looking he steals off and takes a nap. i’ve fired at least five men for doing that, but you can’t teach these mexicans anything. they’ll do exactly as they please in spite of you.”
in fifteen minutes jack and the engineer had set their trap and returned to the cottage again. they were both thoroughly tired and mr. ryder began to take off his things the[99] moment he entered the house. as he unloosened the front of his shirt, however, a rather bulky yellow wallet slipped out and fell to the floor.
“there are those drawings,” said the engineer. “i’d almost forgotten them with all our activities to-day. here’s your wallet, i guess i won’t need it any longer.”
he removed the envelope of blue prints as he spoke and opening the top drawer of his desk dropped it inside, at the same time handing the wallet to jack.
“i’ll be up at six to look for results,” said he as jack started for his room, “but i really don’t expect to find any footprints right off. i rather think the trouble maker has done enough damage to satisfy him for several days at least.”
