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steam goes to a feed water heater, also power than would be needed to yield warmed by furnace gases, where its tem- the same amount using saturated perature is raised to about 170 degrees steam. Of course the superheater costs before it is returned to the boiler. money, so the saving in first cost

Still that does not comprise all the of the plant may not be very great. efforts for economy. The boiler is care- The saving is in operation. In an fully lagged, or covered with a thick ordinary small American steam power jacket of asbestos or other non-conduct- plant, say from twenty-five to two huning material so that the loss of heat by dred horse power, anywhere from three radiation from the boiler is reduced to a to five pounds of coal are required to negligible amount. And there's more yield one horse power for one hour. But yet. Instead of the usual locomotive the lokomobile only requires from 1.2 to type boiler so common among small-sized 1.4 pounds of coal per horse power hour. American steam power plants, with the It has managed to skimp along on one bottom of the grate directly exposed to pound, and on one occasion, during a test the ground so that all the heat possible run, achieved the remarkable record of can be wasted that way, the lokomobile 71 of a pound of coal per horse power has an internal furnace; that is, the fire- hour. That put it far ahead of the gas box is entirely surrounded by water, ex- producer engine which needs, on an avcept at the door. At every possible point erage, one pound of coal per horse power the waste of heat is carefully guarded hour. Now coal costs money, as any one against.

who has to buy it can testify; hence, The net result of all these precautions every dollar saved on the coal bill withis that a very much smaller boiler is re- out reducing the power output is one quired to produce a given amount of hundred cents gained.

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Another advantage of the lokomobile the small American boiler can be cleaned. is that being compressed into the small- The American small boiler never is really est possible space, and also because a cleaned, but gradually accumulates a much smaller boiler and engine are re- thickening coat of scale that renders it quired to produce a given amount of steadily less and less efficient. All these power with superheated than with satu- various things taken together enable the rated steam, less money is required to lokomobile with 200 degrees of superprovide an engine room. Again, being heat to deliver as much as 25 per cent small for the amount of power produced more power than an engine of the same one man can run a good sized plant-say size using saturated steam and at the up to a capacity of 250 horse power— same time show a saving of 25 per cent alone. This, however, is by no means in coal and 33 per cent in boiler feed the limit of size, for lokomobile type water. No wonder under these circumplants are built up to a thousand horse stances that there is an enormous demand power. The one man who runs a loko- for superheat engines all over Europe mobile being necessarily the engineer, is and in other countries as well. Possibly likely to be more competent than the these things may explain why South average fireman, so there is still another Americans prefer to buy their engines of chance to save on the coal pile. While European builders when they might just only one man is needed to run a gas or as well spend their money with their oil engine of pretty large size, it takes northern cousins. an expert mechanic to adjust and repair The importance of using superheated such engines, which not infrequently re- steam in power plants, great as well as quire a deal of tinkering. A lesser de- small, is now universally recognized. No gree of talent suffices to keep a steam fewer than five hundred steamships, most engine going.

of them small, to be sure, though there Furthermore, an internal combustion are some large vessels, including warengine of any kind has a very definite ships with engines of twenty thousand limit on its capacity. A hundred horse horse power, are now equipped with supower internal combustion engine will perheaters. At sea the superheater shows deliver a hundred horse power, if it feels a saving of 12 to 21 per cent in fuel. like it, but it will do no more, no matter Railroad men, too, begin to realize the what inducements are held out. A steam value of the superheater. There are now engine, however, like a music hall artist, more than twelve thousand locomotives is always ready to oblige. If the boss in the world equipped with superheaters, happens to need a hundred and fifty of which more than two thousand are in horse power for an hour or two in an the United States. On the railroad the emergency the hundred horse power superheater effects a saving of about 25 steam engine will help him out. For all per cent in fuel under average working these reasons a number of gas and oil en conditions. This really amounts to an gines have recently been replaced in increase of 33 per cent in the capacity of England by superheat steam engines. the locomotive. To illustrate: A loco

Another notable advantage which the motive burning six thousand pounds of lokomobile has over the ordinary Ameri- coal per hour and developing fifteen huncan type steam plant of small size is the dred horse power would, if equipped with ease with which the boiler can be cleaned. a superheater, produce the same amount The fire box and tubes are built together of power from forty-five hundred pounds. to form one piece and bolted to the boiler But being capable of turning six thouso that by unscrewing a lot of nuts the sand pounds of coal into effective energy .whole interior arrangements can be in an hour, if that amount is now condrawn out of the boiler shell, so that sumed the power output will be increased everything can be thoroughly cleaned, to two thousand horse power—a gain of and then replaced. The operation of tak- 33 per cent. ing the boiler apart and putting it to- It is only the small consumer of steam, gether again consumes five or six hours.. the man who most needs to be saving, Compare this with the clumsy and utterly who does not obtain all the economies inefficient washing which is the only way modern engineering can supply.

DOUBLING THE DIVER'S REACH

By

HENRY GARDINER

MERE twenty-five, fifty or sev- but undertake to go after them right

enty-five feet deeper in the or rather, if we will undertake to return shadowy ocean depths than with sufficient care, after the trip. And divers can now go lies treas- they support their statements by records

ure — treasure of gold and of long experiments and by actual expetreasure of knowledge—that has set the riences of their own. minds of men afire for ages. Within the Nearly everybody who has read the cast of a bass-lure, if it were but on the magazines and newspapers in recent surface, from where the deep-sea worker years has heard of a strange disease, reaches his deadline, sunken argosies and called the "bends,” to which men are strange new forms of life lie side by side, subject who work under great air presyet out of reach.

sures—the fellows, particularly, who go If a false floor existed in the ocean down into the caissons for deep tunneldepths about one hundred and ninety feet work, where compressed air has to be from the surface, things lying deeper used to keep water or mud from coming could not be more hopelessly out of the in upon them to drown them. “Sandgrasp of the diving human being than hogs” and divers alike have been the victhey have been in the past. One hun- tims of the malady, which no one has dred and ninety feet has been the outside very clearly understood. Physicians and limit of the deepest plunging our bodies other scientists have long studied it and would stand, because old ocean would treated it with varying success. Men squeeze the life out of us if we went afflicted with it show symptoms of deeper. The human body will endure asphyxiation, paralysis and other equally only about so much pressure, and pres- serious things, sometimes resulting in sure is the ocean's specialty in those mys- death, often in permanent injury. terious deeps.

Now the investigating Englishmen Four Englishmen have recently come have found out what causes the “bends." forward to declare, how

And in that discovery lies ever, that our notions of

the secret of the new divwhat we can stand have

ing-power they promise us. been too modest. They are

It is a pretty common habit authoritative fellows, too—

of human beings to breathe Dr. Leonard Hill and Mr.

air into the lungs, and one Greenwood, of the London

that the race has never Hospital medical school,

been able, as yet, to shake Prof. J. S. Haldane and

off. The air we breathe is Surgeon Oswald Rees, of

under pressure, normally, the British navy. They say

at sea level, of about fifthat the diver can and shall

teen pounds to the square go — has gone, in fact

inch. At a depth of one more than twice the dis

hundred feet under water, tance mentioned into the

there is a pressure of fortywaters of the sea. They

four pounds to be added to tell us that we can have the

this, when the diver tries to treasures of which we have Diver TAKING A SAMPLE OF AIR reach the low levels. That been despairing, if we will

makes a pressure of fifty

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FROM HIS HELMET FOR SUB

SEQUENT ANALYSIS.

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COLUMN OF A GOAT THAT WAS KILLED

nine pounds, to the square inch of body pounds pressure, with slight variations, surface, that he must resist. At a depth according to our elevation above seaof four hundred feet under water, the level, it behaves very well. Under great pressure reaches the enormous figure of pressure, as in the caissons or under one hundred and ninety-one pounds per water, it acts quite differently. Instead inch—which would be high pressure for of passing peaceably out of the system a locomotive's boiler to contain in regu- as it normally should, it starts a sort of lar work. Hence, when men have game of hide and seek through the bloodessayed to drop

channels, running down to these

off in bubbles into depths, they have

the smaller arteries found conditions

and veins and the that they were not

capillaries, and prepared to meet.

staying there, much Curiously enough,

to the detriment of however, like the

normal functions Irishman who com

in those parts. It plained that it was

is forced out of its not the falling that

regular course of hurt him but “the

progress by the stopping so quick,”

pressure under so it has not been

which it is the diving into

breathed, and high pressures that

crowded off into has cost divers their MICRO-PHOTOGRAPH OF A SECTION OF THE SPINAL places where it does lives or their health, BY SUDDEN DECOMPRESSION.

not belong. Of but the coming up The large bubbles are nitrogen.

course, it makes too rapidly. This

trouble. has been understood in a general way, A man's body is a compressible thing. for some time. In the caissons, where The tissues are soft and capable of rethe sand-hog works, there are air-locks, ceiving the nitrogen under pressure—not through which, by easy stages, a man only capable of receiving, but incapable ascends from the depths and through of resisting. When the diver reaches a slowly lessening pressures, till he reaches point under water where the pressure the surface. The deep-sea divers have becomes high enough to force the nitroobserved something of the same formula gen off into the capillaries in his body, in rising to the surface of the ocean, com- he becomes a fit subject for the “bends," ing up by slow and careful degrees. But, and the only way to save him is to bring even with the greatest care and the most him back to the surface so slowly that intelligent assistance, the men who have the nitrogen, which moves slowly in the risked themselves in this class of work tiny blood-passages, can have time to get have suffered terribly and mysteriously out of them again, before the high presfrom the disease which seemed to be a sure is entirely removed. If he comes up very ally of the sea to prevent our un- too quickly, the nitrogen remains in the covering its secrets.

tissues and he becomes asphyxiated or Now, the "bends” is a strange malady, paralyzed, or something else happens to that has baffled everybody till the four him that is both painful and incapacitatEnglishmen determined to solve the prob- ing, if not actually killing. lem it offered. It is caused by the very Professor Haldane and Surgeon Rees air in the body of the man who contracts experimented with the usual animals, it. When we breathe, we take into our submerging them and bringing them up lungs a combination of oxygen and nitro- to the surface with every conceivable vagen, of which the blood takes the former, riety of method and speed. The guineafor cleansing and fuel purposes. About pigs and dogs and goats that were used eighty per cent of the air, roughly, how- showed all varieties of the disease that ever, is nitrogen. And it is the nitrogen men had been suffering from. They had that causes the "bends." Under sixteen the "bends” as truly as any sand-hog that

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SUBMITTING TO AIR-PRESSURE IN A SPECIALLY

PREPARED TANK.

ever came up too quickly out of the air of the Scottish coast was chosen for the locks. But, patiently changing condi- place of trial, and there these courageous tions and watching results, the experi- men went down to depths of thirty-five menters made a discovery. They found fathoms—two hundred and ten feet—and that if time enough were taken in the actually stayed there and worked as no course of return from high to low air diver has ever attempted to do at much pressures, no “bends” appeared. Then lesser depths. More than that they dethey found that depths could be increased scended and ascended at greater speeds, and pressures

observing only their raised very mate

newly discovered rially, if the return

principle of making to the surface were

the last stage of correspondingly

the ascent slowly ; slow. And then, to

and they felt no ill crown the whole,

effects of any acthey learned that

count whatever. the stage of the

They established return in which it

the fact that divers is really necessary

can go down to the to take time and

depth of thirty-five care, is not the first

fathoms in the asstage— from the

toundingly quick deepest to the less

time of two mindeep depths, from

utes, while, previthe highest to the

ously, the interval medium pressures

prescribed for any—but in the later

thing like similar stages, in the

depths has been change from the medium pressures to close to forty minutes! They found that the normal, at the surface.

it is perfectly safe to ascend rapidly from When they had found out these things, thirty-five fathoms to twelve fathoms, they began a truly remarkable series of thus getting out of the danger-zone of feats. First they showed that a goat high pressure quickly, and thence to come could stand pressures that no man had to the surface more gradually, without ever endured and lived, up to that time. resultant suffering. During the mountMost divers who have approached a ing of the last twelve fathoms of disdepth of one hundred and ninety feet, tance, the body frees itself of all excess have, sooner or later, paid dearly for nitrogen. their temerity. When the goat experi- This is contrary to all accepted methments were ended, however, Mr. Green- ods held as absolute heretofore. But the wood submitted to air-pressure, in a spe- English scientists have established their cially prepared tank, in a degree equal discoveries as facts by long continued and to that at a depth of two hundred and often repeated demonstrations. More, six feet, and suffered no ill effects. More- they have shown by experiments with over, he remained in that pressure for a animals, that the four-hundred-foot depth much longer time than any diver had can be reached with equal safety. And, ever stayed at deep-sea levels. And when now, with their power of endurance he came out of that tank, a new leaf in practically doubled, the divers of the Nature's endless book of knowledge had world can delve after the secrets and the been turned.

treasures of the ocean's bottom in a way Professor Haldane and Surgeon Rees that was only dreamed of before, and can followed Mr. Greenwood with other ex- bring up lost and undiscovered things periments, in which they were the sub- that have tantalized us since ships began jects, and their experiences duplicated to sink and strange forms of unknown his. It remained then to put the results life began to wash up upon our shores to practical application in diver's dress with every visit of the frequent storm

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