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which, did we not see them with our own is but the varying expression of electrical eyes, would be beyond belief. We dwell energy. Someone will be sure to corner in fairyland; and life is worth living, if that; and where shall we be then, I for no other reason than to watch the should like to know. development of society through scientific We no sooner became somewhat acdiscovery and its application to industry. customed to the idea of liquid air than

What strange, self-contained creatures it passed out of mind, and radium prowe are! The marvels that science dis- ceeded to upset our theories. The more closes from day to day are taken as mat I read about radium, the less I know ters of course. People live unheeding in about it. I shouldn't know radium if I the presence of Niagara. Who volun- should meet it in the back yard. In eftarily takes off his hat when a railroad fect it seems to be liquid sunshine, and train thunders by? We notice the elec- entirely beyond a layman's compretric light only to grumble if it goes out. hension. Liquid air, on the contrary, We talk through miles of space, and appeals to the imagination; we can in growl at the telephone girl if there is a a measure grasp the idea. half minute's delay. With no feeling There is something extremely delightsave mild curiosity, we hear whole operas ful in the thought of liquid air, especially emerging from some tiny machine seem to those of us who half believe that air ingly not large enough to contain the exists only in the imagination, until some scale.

storm forces the truth upon us. How As recently as two hundred years ago, seemingly impalpable is air! We move our superstitious ancestors hanged many through it at will. We look out and people supposed to be guilty of witch- cannot see it. We reach out our hand craft and to be able to ride through the and cannot take hold of it. It evades air on broomsticks. To-day, if we mat- the senses. Often only by its absence, ter-of-fact people should happen to see so to speak, can we detect its presence. some modern wizard sailing the circum- Yet, when aroused, no human monument ambient atmosphere astride a stick, we can withstand it. And here is mere man, should look on with some interest per- wizard though he be, who actually freezes haps, but straightway endeavor to im- it to a temperature of 312 degrees below prove the stick and the mode of riding. zero and squeezes it into a liquid. For

I wish to express my appreciation of all we know to the contrary, he will some these tireless men of science. They may day reduce the temperature several hunscare us to death, but we shall never die dred degrees more, squeeze a little of ennui. One feels reconciled to the harder, and store up great chunks of stupendous scheme of the universe and winter weather for the comfort of suffereven to Adam's fall. What if man had ing humanity during July and August. been created with perfect knowledge and A few cubes of frozen atmosphere five Nature had unfolded all of her secrets hundred degrees below zero would not be to him at the start? How stupid it would bad things to turn loose during dog days. be! Now the omnipotent and omni- After all, the imagination stands appresent newspaper places on our break- palled before the possibilities in these fast tables each morning some startling discoveries, liquid air and liquid sunscientific theory or discovery, and life shine, which may be destined to supertakes on new meaning.

sede steam and electricity, make a high A few decades ago, science set us all standard of living inexpensive, and so agog over the missing link; then, that solve in a great degree the social probperplexing conundrum electricity ab- lems of the age. What a time will that sorbed public attention. And man has be, when the industrial world can be run been wandering around ever since in a by wind power, which until now has been bewildering maze of electric undulations, reserved for farmers and orators; when airships, microbes, liquid air, and higher the smoke nuisance shall have been criticism. I am living in constant anx- abated, and one can go down town with iety lest, to-morrow, science will dem- clean linen on his manly bosom and not onstrate that the entire physical universe have it covered with soot before returning! With infinite wonder and pity will the throes of harmony, squeeze it. A posterity read of the smoke nuisance. strong machine ought to stand the pres

Liquid air! Radium! How strange sure. The march properly compressed a story! Perhaps here at last is solved ought, perhaps, to fill an ordinary wine the problem of aërial navigation; and, glass with a most curious liquid which if only the atmosphere extended to Mars, would emit a musical vapor and play for we might hope to cross through space us while we dine. Possibly a whole and pay the people of that far-off planet comic opera, jokes and all, could be held a social visit. But alas! balloons and in a quart dipper. airships cannot travel beyond the atmos How wonderful is science which inphere, and we are prisoners. Fifty miles vades even the arts! A prophetic vision above, could we not anchor at the sur- is upon me, of the seventh son of a face of this great air ocean, and experi- seventh son, born with two veils. I see ment with ether? If only we could see music carted along the street like water, the billows rage and toss in those mighty with signs reading, “Annie Rooney, five convulsions we call storms!

cents a barrel!” “Choice Wagnerian Liquid air! It reminds one of liquid Operas, pint bottles, three dollars a music. Why not? Let some military case !" "Opus Forty-five, One Dollar," band blow one of Sousa's great marches "A few quarts of 'Hiawatha' and 'Beinto the freezing machine. It is a warm delia', left over from last year's stock, tune, but great is science. Then, while will be given away. First come, first the air is still heaving and quivering in served.'

How Did You?
Did you tackle that trouble which came your way

With a resolute heart and cheerful,
Or hide your face from the light of day

With a craven soul and fearful?
Oh, a trouble is a ton, or a trouble is an ounce,

Or a trouble is what you make it!
And it isn't the fact that you're hurt that counts,

But only-how did you take it?
You are beaten to earth? Well, well, what's that?

Come up with a smiling face.
It's nothing against you to fall down flat,

But to lie there-that's disgrace.
The harder you're thrown—why, the higher you bounce;

Be proud of your blackened eye!
It isn't the fact that you're licked that counts;

It's how did you fight-and why?
And though you be done to the death-what then?

If you battled the best you could,
If you played your part in the world of men-

Why, the Master will call it good.
Death comes with a crawl, or comes with a pounce;

And whether he's slow or spry,
It isn't the fact that you're dead that counts,

But only-how did you die?

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In order to receive attention, all inquiries must be addressed to the Consulting Department, and must be accompanied with the full name and address of the sender. In view of the fact that the inquiries already received have far exceeded the available space, the Editors reserve the right to select for publication only those inquiries likely to be of greatest interest to the readers of the mag

azine in general. Other inquiries will be answered by letter.

C. G. S. System-Units of force and

Work Question: Explain the “C. G. S.” system

and work, and give their English values.J. C. V.

Answer: The units of mass, length, and time are said to be "fundamental” units. since all other units, such as those of area, velocity, acceleration, power, etc., are referred to them. These latter units are therefore called "derived" units. The magnitudes of the fundamental units are, however, arbitrary. A large class of writers use the centimeter, gramme, and second, and this system is usually called the "C. G.S." system: others use the foot, pound, and second. It thus becomes important to have a systematic method of reducing measurements from one system of units to another. For strictly scientific purposes, a unit

a unit of work is taken to be the work done by a unit of force when its point of application moves through one foot in the direction of its action ; but, as a convenient and sufficiently accurate standard for practical purposes, the quantity of work which is done in lifting i pound through the height of 1 foot is commonly adopted as the unit, and this quantity of work is spoken of as one foot-pound. It is, however, important to observe that the

foot-pound is not perfectly invariable, since the weight of a pound, and therefore the work done in lifting it through a given height, differs at different places, being a little greater near the Poles than near the Equator.

On the metrical system, the kilogrammeter is the unit; it is the work done when the weight of one kilogramme is raised through a height of one meter. This is equal to 7.24 foot-pounds, and one foot-pound=.1381 of a kilogrammeter.

The unit of force is the poundal. The poundal may be defined as the force necessary to produce an acceleration or gain of velocity of one foot per second, when it acts on a mass of one pound for one second. In the “C. G. S.” system, it is called the dyne, and represents a gain of velocity of i centimeter per second when it acts on a mass of i gramme for one second. In one system the units are given as so many foot-pounds, and in the other so many gramme-seconds.

How to Find a Positive or Negative

Terminal Question: Please explain if there is any way of finding the positive or negative terminal of a generator if we know the direction of motion, the machine being at rest.-H. G. A.

CONSULTING DEPARTMENT-(Continued) Answer: This can be determined by same speed as the gear A. But when Fleming's rule, which states that if we passing a curve, it is quite possible for hold the thumb, first finger, and second either of these gears to turn more slowly finger of the right hand, all three at right than the other and thus permit the deangles, and the thumb represents the di- sired compensation in the movement of rection of motion, the first finger the the wheels. direction of lines of force, then the second finger will represent the direction of current flow. By testing with a com

How to Clean a Boiler pass you can determine which is the Question: What is the best method of north pole of your machine, and knowing cleaning a badly scaled boiler, and what com

he lines of force pass from the north pound should be used ?-A. C. P. pole to the south pole through the air, Answer: First open boiler up, and this will give you their direction. Then note where the loose scale, if any, has apply the rule given you, and you can ob- lodged. Wash out thoroughly, and put tain the direction of current flow. The in the required amount of compound. terminal toward which the current flows While the boiler is in service, open the will be the positive.

blow-off valve for a few seconds, two

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Differential Gear Question: What is the construction and method of working of the differential gear such as is used on the rear axle of an automobile?-N. P. W.

Answer: The accompanying figure shows a form of compensating gear which, with various modifications of de tail, has received a very extensive application. The axle is divided at the center, and, riding on the two abutting ends, is the hub E of the gear or sprocket A. This hub rides loosely upon the axle; and in the body of the gear are the two freely moving bevel pinions C and D. To the two ends of the shafts, the bevel gears B and M are respectively keyed. It is evident that under ordinary conditions on a straight line, the two bevel gears B and I will be rotated with their shafts in the same direction and at the

or three times a day, to be assured that it does not become stopped up with scale.

After running the boiler for a week, shut it down; and, when the pressure is down and the boiler cooled off, run the water out and take off the hand-hole plates. Wote what effect the compound has had on the scale, and where the disengaged scale has lodged. Wash out thoroughly, and use judgment as to whether it is advisable to use a less or greater quantity of compound, or to add a small quantity daily

Continue the washing out at short intervals, as many boilers have been burned by large quantities of scale dropping on the crown sheets and not being removed.

It is necessary to have a chemical analysis of the water used in order fully to CONSULTING DEPARTMENT-(Continued) determine the kind and quantity of com- Answer 5: The accompanying sketch pound to be used. An alkaline com- shows connections required for a compound that has given satisfaction, con- pensator with a three-phase motor. The sists of water, 58 per cent soda-ash, and compensator consists of coils a, b, and c, 70 per cent caustic soda. Proportions, wound on a laminated iron core, each 3,750 gallons of water, 1,600 pounds of coil being provided with a number of soda-ash, and 2,600 pounds of caustic taps, 1, 2, 3, 4, etc. When starting soda. This has been used where the the switch is in the lower position, as principal incrusting solids have been cal shown; and when the motor has reached cium carbonate and sulphate and mag its rated speed, the switch is thrown to nesium sulphate.

the upper or running position, so that

the primary terminals are connected Reversing Rotation and Current Con- directly to the line.

nections of Compensator Question 1: How do you reverse the direction of rotation of a revolving three-phase

Storage Batteries synchronous motor? Question 2: If you reverse the direction of

Question 1: Why are there more negative the current in the fields, will that have any

plates than positive plates in a storage battery? effect on the motor?

Is it absolutely necessary? Question 3: Beginning at the right and lettering the three armature leads A, B, C, if you

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Question 2: What is found on the positive and negative plates of a storage battery when it is charged? And what occurs when the cell is discharged ?

Question 3: How is the capacity of a storage battery usually expressed?-A. P. O.

Answer 1: There are more negative plates than positive in a storage battery, so that each positive plate may have a negative plate on both sides of it. This is perhaps not absolutely necessary, but very desirable.

Answer 2: When a cell is charged, Pb 0, is found on the positive plate and Pb on the negative plate. When the cell is discharged Pb S 0, is found on both plates.

Answer 3: The capacity of a storage battery is usually expressed in amperehours.

effect?

Question 4: Is a compensator a transformer or a reactance coil?

Question 5: Please describe the necessary connections and switches for connecting up a compensator with a three-phase motor.-F. J. M.

Answer 1: The direction of rotation can be reversed by interchanging any two of the leads.

Answer 2: This will have no effect on the motor.

Answer 3: Transposing wires B and C will reverse the direction of rotation.

Answer 4: A compensator is an autotransformer, or a transformer with only one coil; or again, it may be considered a reactance coil.

Overturning of Derricks Question: Will you please tell me why a derrick or derrick car will lift and hold a weight the capacity of the same, if weight is higher than the bottom of the boom of the derrick, but if lowered below that point the car will tilt or the derrick will upset?-C. H. P.

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