Chapter X: MISCELLANEOUS.--Physics without Apparatus.--Illustration (4)

Several influences combine to maintain the circulation of the blood. The pumping action of the heart and the affinity of the blood for the walls of the capillary vessels require to be assisted by the motion both of the body as a whole and of its parts in order to keep the circulation flowing equably through every tissue. Therefore muscular action and the resulting bodily motion play a very important part in maintaining the general and local blood circulation. During the contraction of a muscle, the blood current flowing through it is, for the time being, retarded, but when relaxation occurs the blood flows into its vessels more freely than if no momentary cessation had taken place. When the body or any of its parts is deprived of motion, the blood circulation stagnates, and the nutrition, general or local, as the case may be, promptly becomes impaired. This is specially true of the uterus. Gentle but constant motion is absolutely essential to keep up a healthy uterine blood circulation. Nature has provided for the automatic performance of all the ceaseless internal motions that are necessary to the continuance of life and the preservation of health; thus the heart beats, the respiratory muscles act, the stomach executes a churning motion during gastric digestion, the intestines pass on their contents by worm-like contractions, automatically without our supervision and without causing fatigue, being under the control of the sympathetic system of nerves chiefly. It is equally true, but not so well recognized, that the previously described motions that are committed to the pelvic organs from the respiratory apparatus are absolutely necessary to the continued health of the uterus and its appendages. But the womb is not under the control of the voluntary muscles, therefore it cannot be directly moved by them, nor are its necessary motions influenced by the sympathetic system of nerves as are the heart, stomach, and intestines, etc., but it is fortunately under the indirect but positive control of involuntary muscles that never, as long as breathing continues, cease their work. Nature has thus made ample provision to keep the uterus in automatic motion. As before stated, the natural ceaseless heavings of the lungs, chest, and diaphragm, aided by the muscles inclosing the abdomen, have the duty assigned them of communicating automatic motion to the uterus and the other contents of the pelvis. When the diaphragm descends from A to B, and the lungs are filled with air, the uterus sinks in the pelvic cavity in obedience to the downward pressure from above, as before stated; the circulation through the uterus is then for a moment retarded, but the next instant, when the lungs are emptied of air and the diaphragm rises, the blood flows forward more freely than if it had not been momentarily obstructed. Ample provision has thus been made to maintain a healthy circulation through the uterus.

The uterine motions I have described are fully adequate for the purposes indicated. But when the natural stimulus of motion is withheld, the circulation becomes sluggish causing congestion, which may develop into inflammation. Under these conditions the uterus gradually becomes displaced, falling backward, forward or downward as the case may be. The blood vessels by which the uterus is supplied thus have their caliber diminished by bending; the circulation through them is retarded just as the flow of water in a rubber tube is obstructed by a kink. A very good idea of what occurs in the uterus under the conditions just described may be obtained by winding a string around the fingers.

As the coats of the arteries are thick, and the pressure exerted by the ligature has less power to prevent the arterial blood flowing outward past the string to the end of the finger than it has to prevent the return of the venous blood toward the heart, therefore the part beyond the ligature soon becomes congested, the blood stagnating in the capillaries. If the ligature be sufficiently tight and kept on long enough, mortification will take place, but if the circulation be only moderately obstructed, the congestion will continue until ulceration occurs. A similar condition is developed in the uterus when the necessary natural stimulus of motion fails to be communicated to it or when it is so far out of its proper place that the circulation through it is obstructed.

I believe the above described condition to be a most potent but inadequately recognized cause of the various forms of uterine diseases that distress so many women.

SHOWING HOW THE BREATHING POWERS MAY BE DEVELOPED.

When the circumference of the chest bears a due proportion to the size of the body generally; when its walls and the lungs possess a suitable degree of elasticity; when the strength of the respiratory muscles is adequate to their work, and no undue opposition is offered to the breathing motions by the clothing--then the vital volume is always up to the full requirements of the system. But when one or all of these are lacking in any important degree, the breathing capacity is proportionately diminished. If the testimony of the spirometer be corroborated by the impaired physical condition of the individual, its correction should be sought in part at least by enlarging the chest, increasing the elasticity of its walls and of the lungs, and by augmenting the strength of the respiratory muscles. These results may commonly be secured by diligent and persevering use of the following exercises:

A trapeze, Fig. 2, should be suspended from the ceiling, so that the bar shall be six inches above the head of the person who is to use it; the toes should be placed under straps nailed to the floor to keep them in position. Then if the bar be grasped and the body thrown forward, the trapeze, the arms, and the body will form the segment of a circle.

The exercise is taken by causing the body to describe a complete circle in the manner indicated in the cut. Little muscular effort is required if the motion be rapid, because the momentum is sufficient to carry the body around; but if the rotation be slow, more exertion is required. This movement is specially adapted to the breathing powers of weak persons, yet the most vigorous can readily get from it all the exercise their chest and lungs require.

By means of these exercises the chest is gently but effectively expanded in every direction and the elasticity of its walls promoted, the air cells are expanded, and the lungs are rendered more permeable to the respired air, and the strength of the respiratory muscles is developed.

Fig. 3 illustrates an exercise for the chest that is taken without any apparatus other than an ordinary doorway. The exerciser should stand in the position indicated in the engraving, and then step forward with each foot alternately as far as possible without stretching the chest too severely. The longer the step the more vigorous the exercise will be.

Fig. 4 shows an exercise taken between two chairs; the position indicated in the cut having been assumed, the chest is then slowly lowered and raised three to six times. This exercise is adapted to strong persons only.

THE EFFECTS OF ADEQUATE RESPIRATION IN SPECIAL CASES.

When the nutrition of the body is promoted by effective respiration, and waste matters are promptly removed, the chances that tubercle will be developed in persons who are predisposed thereto are reduced to a minimum.

Better materials are furnished by the nutritive processes to renew the tissues, so that the occurrence of those degenerations that result in various fatal affections, peculiar to the decline of life, are rendered much less probable or are prevented altogether, and the chances that death shall take place by old age is increased. The system possesses much greater resisting power against the influence of malaria and the poisons that give rise to typhoid fever, scarlatina, diphtheria, measles, etc.

When the motions of a woman's respiratory organs are normal and are properly communicated to the pelvic organs, she enjoys the greatest possible immunity attainable against the development of any diseases peculiar to the sex.

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VITAL DISCOVERIES IN OBSTRUCTED AIR AND VENTILATION.[1]

[Footnote 1: Read by Wm. C. Conant before the Polytechnic Association of the American Institute, New York, May 10, 1883.]

I suppose that we all consider ourselves to be sufficiently impressed with the importance of ventilation. If I should stop here to declaim against foul exhalations, or to dwell upon the virtues of fresh air, you might feel inclined to interrupt me by saying, "Oh, we know all about that! If you have anything practical to advance, come to the point." Gentlemen, I beg your pardon, but I must say that the great fact concerning ventilation, as yet, is that its strongest advocates are not conscious of one-half the seriousness of the subject; and the second fact is that the supposed means of ventilation prescribed by science _fail to secure it_.

This, then, is my point to-night--the supreme necessity, still urgent, and _universally_ urgent, for a reformation of the breath of life. I believe in a promised time when the days of a man's life shall again be as the days of a tree. And next to the abolition of vice and sin, I believe that the very grandest factor of such result must be an entire disuse of obstructed air for the lungs. I propose to bring forward some evidence of the necessity, and likewise of the possibility, of a reform so radical and sweeping as this. The subject is too wide for the occasion. I shall be able to read only extracts from what I have prepared, in the few minutes that you can give with patience to my unpracticed lecturing.

The best prescription that doctors have to give (when we are not too far gone to take it) is to live out of doors. Why is this? Why is life out of doors proverbially synonymous with robust health? Why is it that a superior vitality, and a singular exemption from disease, notoriously distinguish dwellers in the open air, by land or sea? Without disparaging the virtues of exercise or of bracing temperature, indispensable as these are for the recuperation of enfeebled constitutions, we must admit that among the native and settled inhabitants of the open air high health is the rule in warm climates as well as in cold, and with the very laziest mortals that bask in the sun, or loaf in the woods. The fact is that simple vegetative health seems to be nearly independent of all other external conditions but that of a pure natural diet for the lungs. Man in nature seems to thrive as spontaneously as plants, by the free grace of air, earth, and sun. On the other hand, the very diseases from which houses are supposed to defend us--that most numerous class resulting from colds--are the special scourge of the lives that are most carefully shielded from their commonly supposed cause--exposure to the open air. Those diseases diminish, and entirely disappear, just so far as exposure in the pure and freely moving air becomes complete and habitual. Soldiers, inured to camp life, catch cold if they once sleep in a house; and, generally speaking, the inhabitants of the free air contract colds _only_ by exposure to confined exhalations from their own or other bodies, within the walls of houses. The explanation of this is plain and simple: Carbonic acid detained within four walls accumulates in place of the breath of life--oxygen--and narcotizes the excretory function of the skin. The moment that this great and continual vent of waste and impurity from the system is obstructed, internal derangement ensues in every direction. All hands, so to speak, are strained to extra duty to discharge the noxious accumulation. The lungs labor to discharge the load thrown back upon them, with hastened respiration, increased combustion, and feverish heat. The pores of the mucous membrane in the nose, throat, alimentary canal, or bronchial passages, are forced by an aggravated discharge (or catarrh), and this congestive and inflammatory pressure is a fever also. There is nothing of "cold" about it except as an auxiliary and antecedent, in cases where an external chill has struck upon nerves already half paralyzed by the universal narcotic--carbonic acid--which house dwellers may be said to "smoke" perpetually.

So much for nerve-poison; but blood-poisoning is a still more terrible characteristic of house-protected existence. It is now the almost universal opinion of the medical profession that the whole class of malarial and zymotic diseases that make such frightful progress and havoc in the most civilized communities, are due to living germs with which the exhalations of organic waste and decay are everywhere loaded in inconceivable numbers. They are known to multiply themselves many times over, every two or three hours. They swarm into the blood by millions, through all the absorbents, especially those of the lungs, that drink the atmosphere in which they are suffered to linger and propagate. Mr. Dancer, the eminent microscopist, counted in a sample from such an atmosphere a number of organized germs equivalent to 3,700,000 in the volume of air hourly inhaled by one person. That is over 60,000 germs per minute, and about 2,000 in every breath. In the blood, they still propagate, and feed, and grow, consuming its oxygen, thus defeating its purification, and turning that stream of otherwise healthful and invigorating nutrition into a stream of effete and corrupt matter--a sewer rather than a river of life--or at best an impoverished and impure supply for the support of existence.

The same pestilential but invisible hosts of bacteria, mustered and bred in the close filthiness of Oriental cities, and jungles, swarm out as Asiatic cholera on the wings of the wind, sweeping the wide world with havoc. Settled on the tropical shores of the Eastern Atlantic, they lie in wait for their victims in the sluggish and terrible coast fever. On the western coast of the same ocean, perhaps from some cause connected with oceanic or atmospheric currents, they make devastating irruptions inland, as yellow fever, in every direction where the walls of their enclosure are low enough to be freely passed. These, let us remember, are all essentially the same organic poison that is engendered _wherever_ life and death are plying their perpetual game; and this, like Cleopatra's "worm, will do its kind" in the veins of man, wherever obstructions, natural or artificial, temporary or permanent, interfere with its prompt diffusion in the vastness of the general atmosphere. Our "house of life" stands generously open, for every "inmate bad" to come and go through the absorbent, unquestioned, except in the stomach, where the tangible poisons have to go by the act of swallowing and where they are often challenged and ejected. It seems at first thought very strange that we are not so well protected by natural instinct or sensibility from the subtle poisons of the atmosphere as from those that can affect us only by the voluntary act of swallowing. The obvious explanation, however, of this apparent neglect is that Nature protects us in general from gaseous poisons by her own system of ventilation; and if, when we devise houses, necessarily excluding that system, we fail to devise also a sufficient substitute for it, the consequences of such negligence are as fairly due as when we swallow tangible poison.

I have hitherto referred only to the _dispersion_ of poisonous exhalations, as if the best and most necessary thing the atmosphere can do for us were to dilute the dose to a comparatively harmless potency. But this is now known to be not the true remedial process with respect to the zymotic germs. The most wonderful achievement of recent investigation reveals a philosophy of both bane and antidote that astonishes us with its simplicity as much as with its efficiency. At the moment when humanity stands aghast at the announcement that germs are not destroyed by disinfectants, comes the counter discovery that they are rendered harmless by oxygen. It seems that it makes no difference, really, of what sort or from what source are the bacteria that we take into the blood. The only material difference to us depends on _the sort of atmosphere_ in which their hourly generations are bred. For example, the bacteria _developed in confined air_, from a simple infusion of hay, are found by experiment to be as capable of generating that most terrible of blood poisoners, the malignant pustule, as are the bacteria taken from the pustule itself.

On the other hand, the bacteria from the malignant pustule itself, after propagating for a few hours in pure and free air, become a perfectly harmless race, and are actually injected into the blood with impunity. The explanation of the strange discovery is this--note its extreme simplicity--bacteria bred in copious oxygen perish for want of it as soon as they enter the blood vessels; whereas those inured to an unventilated atmosphere for a few generations, which means only a few hours, are prepared to thrive and propagate infinitely within our veins; and that is the whole mystery of blood poisoning and zymotic diseases. Taken in connection with the narcotic or _nerve-poisoning_ power of carbonic acid (to which all the classes of diseases resulting from colds are due), we have also in this simple but grand discovery the whole mystery of the question with which we set out--why free air is health, and why sickness is a purely domestic product. The restitution of natural health to mankind demands only, but demands absolutely, the constant diffusion in copious and continuous floods of atmospheric oxygen, of the nerve-poisoning carbonic acid of combustion (organic and inorganic), and of the blood-poisoning bacteria of organic decomposition.

We find, then, as a matter both of experience and of philosophy, that life or death, in the main and in the long run, turns on the single pivot of atmospheric movement or obstruction. The resistance of mere rising ground or dense vegetation to a free movement of the air from low-lying levels performs an obstructive office similar to that of the walls and roofs of houses, and with like effect. The invariable condition of unhealthy _seasons_ and _days_ is a state of rarefaction and stagnation of the atmosphere, when the poison-freighted vapor cannot be lifted and dispersed, and every one complains of the sultry, close, "muggy" (meaning _murky_) feeling of the air. Few reflect, when fretted by the boisterous winds of March, upon the vital office they perform in dispersing and sanitating the bacteria-laden exhalations let loose by the first warmth from the soaked soil and the macerated deposits of the former year.

The passing air, then, that we breathe so lightly, is on other business, and carries a load we little think of, and that is not to be trifled with. This grand carrier of nature, on business of life or death, must not be detained, must not be hindered! or they who interfere with the business by restraining walls and roofs will take the consequences. It is a good deal like stopping a bullet, except as to consciousness and suddenness of effect.

That men live at all in their obstructed and therefore poison-loaded atmosphere, is a proof of the wonderful efficiency of the protective economy of Nature within us; so wonderful, indeed, that few can believe the fact of living to be consistent with the real existence of such a deadly environment as science pretends to reveal. It is a common impression, therefore, that actual results fail to justify the alarm sounded by sanitarians. Hence the necessity for calling attention at the outset to an ample and manifest equivalent for the deadly dose of confined exhalations taken daily by all civilized men. We perceive that that dose is not lost, like the Humboldt River, in a "sink," but reappears, like the wide-sown grass, in a perennial and universal crop of diseases, almost numberless and ever increasing in number, peculiar to house-dwellers. The trail of these plagues stops nowhere else; it leads straight to the imprisoned atmosphere in our artificial inclosures, and there it ends. That marvelous protective economy of Nature within us, to which we have referred, is no perpetual guaranty against the consequences of our negligence; it is only a limited reprieve, to afford space for repentance; and unless we hasten to improve the day of grace, the suspended sentence comes down, upon us at last with force the more accumulated by delay.

Now, therefore, the grand problem of sanitary science (almost untouched, almost unrecognized) proves to be no other and no less than this:

What can be done to remedy the obstructive nature of an inclosure, so that its gaseous contents shall _move off_, and be replaced by pure air, as freely, as rapidly, and as incessantly, as in the open atmosphere?

It happens to be the most necessary preliminary in approaching this problem, to show how _not_ to do it, for that, respectfully be it spoken, is what we have hitherto practiced, as results abundantly prove. Fallacies, both vulgar and scientific, obstruct our way. A fundamental fallacy respects the very nature of the work, which is supposed to be _to get in fresh air_. In point of fact, this care is both unnecessary and comparatively useless. Take care of the bad air, and the fresh air will take care of itself. Only make room for it, and you cannot keep it out. On the other hand, unless you first make room for it, you cannot keep it _in_; pump it in and blow it in as you may, you only blow it _through_, as the Jordan flows comparatively uncontaminated through the Dead Sea. This is a law of fluids that must be kept in view. The pure air is quite as ready to get out as to get in; while the air loaded with poisonous vapors is as sluggish as a gorged serpent, and will not budge but on compulsion. Such compulsion the grand system of wind _suction_, actuated by the sun, supplies on the scale of the universe; and this we must imitate and adapt for our more limited purposes.

It would seem as if we need not pause to notice so shallow though common a notion as that which usually comes in right here, namely, that confined air will move off somehow of itself, if you give it liberty; being supposed to be much like a cat in a bag, wanting only a hole to make its escape. Air is ponderable matter--as much so as lead--and equally requires force of some kind to set it or keep it in motion. But applied philosophy itself relies on a fallacious, or, at best, inadequate source of motive power for ventilation. It gravely prescribes ventilating flues and even holes, and promises us that the warmed air within the house will rise through these flues and holes, carrying its impurities away with it, from the pressure of the cooler and denser air without. But we very well know that the best of flues and chimneys will draw only by favor of lively fires or clear weather. They fail us utterly when most needed, in warm and murky weather, when the barometer is low, and the thin atmosphere drops, down its damp and dirty contents, burying us to the chimney tops in a pestilent congregation of vapors.

Nevertheless, so far as I can discover, these holes and flues, at best a little fire at the bottom of the latter, are the sole and all-sufficient expedients of science and architecture for ventilation to this _day_, in spite of their total failure in experience. I can find nothing in standard treatises or examples from philosophers or architects, beyond a theoretical calculation on so much expansion of air from so many units of heat, and hence so much ascensional force _inferred_ in the ventilating flue--a result which never comes to pass, yet none the less continues to be cheerfully relied on. Unfortunately for the facts, they contradict the philosophy, and are only to be ignored with silent contempt. A French Academician's report on the ventilation of a large public building, lately reprinted by the Smithsonian Institution, states with absolute assurance and exactness the cubic feet of air changed per minute, with the precise volume and velocity of its ascension, by burning a peck of coal at the bottom of the trunk flue. No mention is made of the anemometer or any other gauge of the result asserted, and we are left to the suspicion that it is merely a matter of theoretical inference, as usual; for every one who has had any acquaintance with practical tests in these matters knows that no such movement of air ever takes place under such conditions, unless by exceptional favor of the weather.

I have seen a tall steam boiler chimney induce through a four inch pipe a suction strong enough to exhaust the air from a large room as fast as perfect ventilation would require. But this, it is well known, requires four hundred or five hundred degrees of heat in the chimney. I never saw an ordinary domestic fire of coals produce any noticeable ventilating suction, without the use of a blower, urging the combustion to fury, and I presume nobody else ever did.

But, while nobody ever saw an active suction of air produced by the mere heat of a still or unexcited fire--unless the _quantity_ of heat were on a very large scale--everybody has seen a roaring current sucked through the narrowed throat of a chimney or a stove by a blazing handful of shavings, paper, or straw. It is very remarkable, when you come to think of it, that the burning of an insignificant piece of paper, with less heat in it, perhaps, than a pea of anthracite, will cause a rush of air that a bushel of anthracite cannot in the least degree imitate. It is not only a curious but a most important fact. In short, it is _the cardinal_ fact on which ventilation practically turns. But what is the nature of it? There are three factors in the phenomenon. In the first place, the mechanical peculiarity of flame, or gas in the moment of combustion, as compared with a gas like air merely heated, is _an almost explosive velocity of ascent._ The physical peculiarity from which this results is the intensity of its heat--commonly stated at 2,000 degrees, as to our common illuminating gas--acting instantaneously throughout its mass, just as in gunpowder. The gas goes up the flue in its own flash, like the ignited charge in the barrel of a gun: the burning coals can only _send_, and by a leisurely messenger, namely, the moderately heated gases, and contiguous air, that rise only by the gravitation or pressure of the surrounding atmosphere.

And yet it is not the small flame itself that roars in the chimney but the rush of air induced by it. The semi-explosion of flame is but for an instant, though constantly renewed, and its explosive impulse cannot carry its light products of combustion very far through stationary and resistant air. It is _the induction of air_ carried with it by such semi-explosive impulse (under proper mechanical conditions) that is strange to our observation and understanding, and is the second factor in the phenomenon we are accounting for and preparing to utilize.

The process, as it actually is, may be clearly exhibited by a very simple means. Let anyone take a tube, say an inch in diameter--a roll of paper will do as well as anything--and, applying it closely to his mouth, try the whole force of his lungs through it upon any light object. The amount of effect will be found surprisingly small; and unless the tube is a short one, it will be so far absorbed by friction and atmospheric resistance as to be almost imperceptible. Then let him hold the same tube near to the mouth, but not in contact, and repeat the experiment. With the best adjustment, the effect may be described as tenfold or fifty-fold, or almost any fold--the effect of the simple blowing being merely nominal as compared with the induced current added by blowing _into_ the tube instead of _in_ it. The blast enters the free and open orifice with all the contiguous air which its surface friction and the vacuum of its movement can involve in its rolling vortex. While the entrance is thus crowded with pressure, the exit is free; and the result at the exit is a blast of well sustained velocity and _magnified volume;_ ready itself to repeat the miracle on a still larger scale if provided with the apparatus for doing so. To test this, now place a second and larger tube in such position as to prolong the first in a straight line, but with a slight interval between the meeting ends; so that the blast, as magnified in volume in entering the first tube, may enter in like manner the second tube and be magnified again. With correct adjustments this experiment will prove more surprising than the first. Put on a third and still larger tube in the same way, and still larger surprise will meet a still larger volume and force of blast, like a stiff breeze set in motion by the puny effort of a single expiration. Of course, the prime impulse must bear a certain proportion to the result; and the inductive or tractional friction of the initial blast, of flame or breath, will be used up at length unless re-enforced. In ventilating practice, there _is_ such re-enforcement, from an excess of gravity in the cooler atmosphere outside the flue in which the flame is operating with its heat as well as its ascensional traction; so that there has been found no limit to the extensions and fresh inductions that may be added to the first or trunk flue, with increase rather than diminution of power at every point. But the terms on which such extensions must be made have been referred to in our illustration, and must be accurately ascertained and observed. They constitute what is, in effect, the third factor in the phenomenon of a roaring draught, and also, therefore, ineffective ventilation. That is, the entering or induced current of air must always find its channel of progress and exit certain correct degrees larger than the opening by which it entered. Every one knows that a stove or chimney wide open admits of but little suction in connection with even the blaze of paper or shavings.

The mobility of air seems almost preternatural, when the proper conditions for setting a current in motion are supplied. But without a current established, it is surprising in turn to find how obstinately and elusively immovable it can be. It is like tossing a feather; or trying to drive a swarm of flies; dodging and evading every impulse applied. But, given a flue, to define and conduct a stream; an upright flue, to take advantage of the slighter gravity of the warmed air within it; and a flue contracted at the inlet and expanded as it rises, so as to free, diffuse, and lighten the column of air, toward the exit; _then_, initiate an induced current of air at the inlet, by the injection of a jet of gas in the state of semi-explosive action called flame; the pressure pushing upward from the crowded entrance finds easier way and less resistance the farther it goes in the expanding flue; the warmth and reduced gravity of the stream comes in as an auxiliary in overcoming friction and any exceptional obstruction in the state of the atmosphere; and now, as the ball is once set rolling, with a little _aid_ instead of resistance from gravitation, its initial impulse all the while sustained by the gas jet, and friction reduced to a very small incident--there is nothing to prevent the current rolling on with accelerated velocity (within the limitations imposed by increasing friction) and rolling on forever. I might, if I had time, add a curious consideration of the law of _vortex motion_ in elastic fluids, demonstrated by Helmholtz, which relieves the motion of such fluids from friction, as wheels facilitate the movement of a solid; and which also sucks into the rolling vortex the contiguous air, thus entraining it, as we have seen, so much more effectively than could be done by a direct and rigid current, like a jet of water, for instance. A wheel set in motion on an almost frictionless bearing of metalline, runs without perceptible abatement of velocity, until one begins to involuntarily question whether it will ever stop. In the all but free winds that roll with minimized friction in the higher atmosphere, there seems to be a self-moving force; so persistent is simple momentum in a mass so infinitesimally obstructed and so infinitely wheeled. An active current of air in a ventilating flue is only less perfect in the same conditions; and so it is quite conceivable, and not incredible, that such a current may be gradually established and thenceforward permanently maintained by a small motor flame barely more than enough to overbalance the minimized friction. This is not a supposed or theoretically inferred fact, like the facts of ventilation sometimes alleged by theorists. On the contrary, the theory I have offered is merely an attempt to explain facts that I have witnessed and that anyone can verify with the anemometer. But the _theory_ by no means covers the art and mystery of ventilation; for ventilation is truly an _art_ as well as a mystery. The art lies in a consummate experience of the sizes, proportions, and forms of flues, their inlets, expansions, and exits, with many other incidental adaptations necessary, in order to insure under _all_ circumstances the regular exhaustion of any specific volume of air required, per minute. And this art has by one man been achieved. It would be a double injustice if I should neglect from any motive to inform my audience to whom I am indebted for what I know about ventilation practically, and even for the knowledge that there is any such fact as a practicable ventilation of houses; one who is no theorist, but who has felt his way experimentally with his own hands, for a lifetime, to a practical mastery of the art to which I have attempted to fit a theory; every one present who is well informed on this subject must have anticipated already in mind the name of Henry A. Gouge.

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THE RECENT ERUPTION OF ETNA.

On the morning of the 20th of March, a long series of earthquakes spread alarm throughout all the cities and numerous villages that are scattered over the sides of Mt. Etna. The shocks followed each other at intervals of a few minutes; dull subterranean rumblings were heard; and a catastrophe was seen to be impending. Toward evening the ground cracked at the lower part of the south side of the mountain, at the limit of the cultivated zone, and at four kilometers to the north of the village of Nicolosi. There formed on the earth a large number of very wide fissures, through which escaped great volumes of steam and gases which enveloped the mountain in a thick haze; and toward night, a very bright red light, which, seen from Catania, seemed to come out in great waves from the foot of the mountain, announced the coming of the lava.

Eleven eruptions occurred during the night, and shot into the air fiery scoriae which, in a short time, formed three hillocks from forty to fifty meters in height. The jet of scoriae was accompanied with strong detonations, and the oscillations of the ground were of such violence that the bells in the villages of Nicolosi and Pedara rang of themselves. The general consternation was the greater in that the locality in which the eruptive phenomena were manifesting themselves was nearly the same as that which formed the theater of the celebrated eruption of 1669. This locality overlooks an inclined plane which is given up to cultivation, and in which are scattered, at a short distance from the place of the eruption, twelve villages having a total population of 20,000 inhabitants. On the second day the character, of the eruption had become of a very alarming character. New fissures showed themselves up to the vicinity of Nicolosi, and the lava flowed in great waves over the circumjacent lands. This seemed to indicate a lengthy eruption; but, to the surprise of those interested in volcanic phenomena, on the third day the eruptive movement began to decrease, and, during the night, stopped entirely. This was a very fortunate circumstance, for this eruption would have caused immense damages. It cannot be disguised, however, that the eruptive attendants of this conflagration remain under conditions such as to constitute a permanent danger for the neighboring villages. It has happened, in fact, that in consequence of the quick cessation of the eruption, those secondary phenomena through which nature usually provides a solid closing of the parasitic craters have not occurred. So it is probable that when a new eruption takes place it will be at the same point at which manifested itself the one that has just abated.--_La Nature_.

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PHYSICS WITHOUT APPARATUS.

Take an ordinary wine bottle and place it in front of and within a few inches of a lighted candle. Blow against the bottle with your mouth at about four or six inches distant from it and in a line with the flame. Very curiously, notwithstanding the presence of the bottle and its interception of the current of air, the candle will be immediately extinguished as if there were no obstacle in the way. This phenomenon is readily understood when we reflect that the bottle receives the current of air on its polished surface and divides it into two, one of which is guided to the right and the other to the left. These two currents, after separating and driving back the surrounding air, meet again at the very spot at which the flame is situated, and extinguish the candle.

It is evident that the experiment can be reproduced by putting the candle behind a stove pipe, a cylinder of glass or metal, a cylindrical tin box, or any other object of the same form with a diameter greater than that of a bottle, but not having a rough or angular surface, since the latter would cause the current to be lost in the surrounding air.

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THE TRAVELS OF THE SUN.

Some recent discussions of the constitution of the sun have turned in part upon what is known as the sun's proper motion in space. This is one of the most surprising and interesting things that science has ever brought to light, and yet it is something of which comparatively few persons have any knowledge. It is customary to look upon the sun as if it were the center of the universe, an immovable fiery globe around which the earth and other planets revolve while it remains fixed in one place. Nothing could be further from the truth. The sun is, in fact, the most wonderful of travelers. He is flying through space at the rate of not less than a hundred and sixty millions of miles in a year, and the earth and her sister planets are his fellow voyagers, which, obeying his overpowering attraction, circle about him as he advances. In other words, if we could take up a position in open space in advance of the sun, we should see him rushing toward us at the rate of some 450,000 miles a day, chased by his whole family of shining worlds and the vast swarms of meteoric bodies which obey his attraction.

The general direction of this motion of the solar system has been known since the time of Sir William Herschel. It is toward the constellation Hercules, which, at this season, may be seen in the northeastern sky at 9 o'clock in the evening. As the line of this motion makes an angle of fifty odd degrees with the plane of the earth's orbit, it follows that the earth is not like a horse at a windlass, circling around the sun forever in one beaten path, but like a ship belonging to a fleet whose leader is continually pushing its prow into unexplored waters.

The path of the earth through space is spiral, so that it is all the time advancing into new regions along with the sun. She is on a boundless voyage of discovery, and her human crew are born and die in widely separated tracts of space. Think of the distance over which the travels of the sun have borne the earth only since the beginning of human history! Six thousand years ago the earth and sun were about a million millions of miles further from the stars in Hercules than they are to-day. Columbus and his contemporaries lived when the earth was in a region of the universe more than sixty thousand millions of miles from the place where it is now, so that since his time the whole human race has been making a voyage through space, in comparison with which his longest voyage was as the footstep of a fly.

Thus the great events in the history of the world may be said to have occurred in different parts of the universe. An almost inconceivable distance separates the spot which the earth occupied in the time of Alexander from that which it occupied when Caesar invaded Gaul. The sun and the earth have wandered so far from their birthplace that the mind staggers in the attempt to guess at the stupendous distance which now probably separates them from it. It may be that the motion of the solar system is orbital and that our sun and many of the stars, his fellow suns, are revolving around some common center, but if so, no means has yet been devised of detecting the form or dimensions of his orbit. So far as we can see, the sun is moving in a straight line.

Since space is believed to be filled with some sort of ethereal medium, curious consequences are seen to follow from the motions that have been described. A solid globe like the earth rushing at great speed through such a medium will encounter some resistance. If the medium be exceedingly rare, as it must be in fact, the resistance will be correspondingly small, but still there will be resistance. If the sun stood still, the earth, owing to the inclination of its axis to the plane of its orbit, around the sun, would encounter the resistance of the ether principally on its northern hemisphere from summer to winter, and on its southern hemisphere from winter to summer. But in consequence of the motion of the sun shared by the earth, this law of distribution is changed, and from summer to winter the earth plows through the ether with its north pole foremost, while from winter to summer, although the resistance of the ether is encountered more evenly by the two hemispheres, yet it is still felt principally in the northern hemisphere, and the south pole remains practically protected. It follows that the southern hemisphere, and particularly the south polar regions are more or less completely sheltered the whole year around. It might then be supposed that the impact of the particles of the ether shouldered aside by the earth in its swift flight and the compression produced in front of the advancing globe would tend to raise the temperature of the northern hemisphere as compared with the southern hemisphere, while the south pole, being more or less directly in the wake of the earth, and in a region of rarefaction of the ether, would constantly possess a remarkably low temperature.

Now, it is known that the south polar regions are more covered with ice and snow than those of the north, and that the temperature there the year around is lower. Whether this difference is owing to the effects of the earth's journey through the ether, is a question.

The sun, too, moves with his northern hemisphere foremost, and it is worthy of remark that it has been suspected that the northern hemisphere of the sun radiates more heat than the southern.

But whatever effect it may or may not have upon the meteorological condition of the earth, the fact that the solar system is thus voyaging through space is in itself exceedingly interesting. Not the wildest traveler's dream presents to the imagination such a voyage as this on which every inhabitant of the earth is bound. A glance at a star map shows that the direction in which we are going is carrying us toward a region of the heavens exceedingly rich in stars, many, and perhaps most, of which are greater suns than ours. There can be little doubt that when the sun arrives in the neighborhood of those stars, he will be surrounded by celestial scenery very different from and much more brilliant than that of the region of space in which he now is. The inhabitants of the globe at that distant period will certainly behold new and far more glorious heavens, though the earth may be unchanged.--_N.Y. Sun._

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PROPAGATION OF MAPLE TREES.

I do not presume that all people over three score years of age are so entirely ignorant as I am, but probably there are some. I have lived more than sixty years almost in the woods, and I never observed, and never heard any other person speak of, the blooming, seeding, and maturing of the water maple. I have a beautiful low of water maple shade trees along the street in front of my house. In March, 1882, I observed that they were in bloom, and many bees were swarming about them. After the bees left them I noticed the seed (specimens inclosed of this spring's growth) in millions. As the leaves put out in April the little knife blade seeds fell off, so thick as to almost cover the ground. My grandson picked up three or four hatfuls, and I sent the seed to my farm and had them drilled in like wheat, when I planted corn. The result is I have from 300 to 500 beautiful maples from 6 inches to three feet high. I noticed the blooms again this spring, but a cold snap killed the blooms, and only now and then can I find a seed. I had a sugar tree in my yard, which bloomed and bore seed which did not fall off through the summer. My yard now has as many little sugar trees as it has leaves of blue grass.

It strikes me that the gathering and planting of maple seed is the best way to wood the prairies of the West and the worn-out lands of the Eastern and Middle States. The tree is valuable for shade and for timber, and is as rapid in growth as any tree within my knowledge. I noticed some trees of this sort yesterday which are from 21/2 to 31/2 feet in diameter. The lumber from such timber makes beautiful furniture. This is intended only for those who have been as non-observant as myself, and not the wise, who are always posted.

Franklin, Tenn. J.B.M.

The seeds inclosed were the samaras of _Acer rubrum_, called the "soft" maple in many localities, and "red" maple in others. We have seen trees only three or four inches in diameter full of blossoms. This is one of the earliest trees to bloom in spring, and the pretty winged samaras soon mature and fall. The sugar maple, _Acer saccharinum_, blossoms later, and the seeds are persistent till autumn, and lie on the ground all winter before germinating. The lumber from this latter is more valuable than soft maple, being harder, heavier, and taking a better polish. Soft maple makes an ox-yoke which is durable and not heavy. In early times a decoction of the bark was frequently used for making a black ink.--_Country Gentleman._

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DIOSCOREA RETUSA.

One of the most elegant plants one can have in a greenhouse is this twiner, a native of South Africa. It has slender stems clothed with distinctly veined leaves, and produces a profusion of creamy white fragrant flowers in pendulous clusters, as shown in the annexed engraving, for which we are indebted to Messrs Veitch of Chelsea, who distributed the plant a few years ago. On several occasions Messrs Veitch have exhibited it trained parasol fashion and covered abundantly with elegant drooping clusters of flowers, and as such it has been much admired. When planted out in a warmish greenhouse and allowed to twine at will around an upright pillar, it is seen to the best advantage, and, though not showy, makes a pleasing contrast with other gayly tinted flowers. It is so unlike any other ornamental plant in cultivation, that it ought to become more widely known than it appears to be at present.--_The Garden._

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RAVAGES OF A RARE SCOLYTID BEETLE IN THE SUGAR MAPLES OF NORTHEASTERN NEW YORK.

About the first of last August (1882) I noticed that a large percentage of the undergrowth of the sugar maple (_Acer saccharinum_) in Lewis County, Northeastern New York, seemed to be dying The leaves drooped and withered, and finally shriveled and dried, but still clung to the branches.

The majority of the plants affected were bushes a centimeter or two in thickness, and averaging from one to two meters in height, though a few exceeded these dimensions. On attempting to pull them up they uniformly, and almost without exception, broke off at the level of the ground, leaving the root undisturbed. A glance at the broken end sufficed to reveal the mystery, for it was perforated, both vertically and horizontally, by the tubular excavations of a little Scolytid beetle which, in most instances, was found still engaged in his work of destruction.

At this time the wood immediately above the part actually invaded by the insect was still sound, but a couple of months later it was generally found to be rotten. During September and October I dug up and examined a large number of apparently healthy young maples of about the size of those already mentioned, and was somewhat surprised to discover that fully ten per cent. of them were infested with the same beetles, though the excavations had not as yet been sufficiently extensive to affect the outward appearance of the bush. They must all die during the coming winter, and next spring will show that, in Lewis County alone, hundreds of thousands of young sugar maples perished from the ravages of this Scolytid during the summer of 1882.

Dr. George H Horn, of Philadelphia, to whom I sent specimens for identification, writes me that the beetle is _Corthylus punctatissimus_, Zim, and that nothing is known of its habits. I take pleasure, therefore, in contributing the present account, meager as it is, of its operations, and have illustrated it with a few rough sketches that are all of the natural size, excepting those of the insects themselves, which are magnified about nine diameters.

The hole which constitutes the entrance to the excavation is, without exception, at or very near the surface of the ground, and is invariably beneath the layer of dead and decaying leaves that everywhere covers the soil in our Northern deciduous forests. Each burrow consists of a primary, more or less horizontal, circular canal, that passes completely around the bush, but does not perforate into the entrance hole, for it generally takes a slightly spiral course, so that when back to the starting point it falls either a little above, or a little below it--commonly the latter (see Figs. 1 and 2).

It follows the periphery so closely that the outer layer of growing wood, separating it from the bark, does not average 0.25 mm. in thickness, and yet I have never known it to cut entirely through this, so as to lie in contact with the bark.

From this primary circular excavation issue, at right angles, and generally in both directions (up and down), a varying number of straight tubes, parallel to the axis of the plant (see Figs. 1, 2, and 3). They average five or six millimeters in length, and commonly terminate blindly, a mature beetle being usually found in the end of each. Sometimes, but rarely, one or more of those vertical excavations is found to extend farther, and, bending at a right angle, to take a turn around the circumference of the bush, thus constituting a second horizontal circular canal from which, as from the primary one, a varying number of short vertical tubes branch off. And in very exceptional cases these excavations extend still deeper, and there may be three, or even four, more or less complete circular canals. Such an unusual state of things exists in the specimen from which Fig 3 is taken.

It will be seen that with few exceptions, the most important of which is shown in Fig 4, all the excavations (including both the horizontal canals and their vertical off shoots) are made in the sap-wood immediately under the bark, and not in the hard and comparatively dry central portion. This is, doubtless, because the outer layers of the wood are softer and more juicy, and therefore more easily cut, besides containing more nutriment and being, doubt less, better relished than the drier interior.