Puslapio vaizdai
PDF
„ePub“

How shall there be repair when the food material out of which the repair is secured is not supplied ? For a starving man to sleep and die we might be prepared ; for a starving man to awake in the shadow of semi-consciousness or dementia ; for a starving man to wake in the terror and excitement of delirium and rage ;'for any one of these conditions we might be prepared. But for such a man to wake up refreshed and, at the worst, no more than irritable and pettish, is not by any means a condition easy to be classed amongst the probable phenomena of nature. It would be sheer vanity and conceit to say that a fact of this order is not new to science and is not worthy of a place in the annals of scientific research.

VII. The last and most obvious teaching from these fasting experiences consists in the old, but now more demonstrative, evidence of the grand part which water plays in the economy of life. The physiologist, who knows that about seventy-five per cent of the human body is made up of water, will not wonder, so much as others will that water should possess the life-sustaining power which now is seen to belong to it. Yet he will be perplexed with the new readings, which are presented as to the mode by which it sustains for so long a period of time. He will see that under its influence a kind of peripheral digestion is established in the body itself, by which, independently of the stomach, the body can subsist for a long time on itself ; first on its stored-up or reserve structures, and afterwards on its own active structures. He will infer that, by the influence of the water imbibed, the digestive juices of the stomach are kept from acting on the walls of the stomach. He will discern that, by the steady introduction of water into the blood, the blood corpuscles are kept in a state of vitality and in a condition fitted for the absorption of oxygen from the air. He will note that the minute vesicular structures of the lungs and of all the glandular organs are kept also vitalised and physically capable of function; and he will understand how, by the same agent, that water-engine the brain is sustained in activity, its cement fluid, and its cellular structure free. There will, nevertheless, be much still left to afford him food for contemplation; and, even if he thinks these fasters are not the wisest of men, he will hardly be averse to distil from them such essence of philosophy as may be legitimately extracted.

a

BENJAMIN WARD RICHARDSON.

367

SCIENCE NOTES.

VERYBODY is now interested in the progress of science, and

wishes to know something about it; but only those who have little else to do can follow it in the voluminous records where scientific discoveries are originally announced. Even to read the two or three English journals where these are epitomised is too much for most of us, seeing that everything available is heaped together therein ; and nine-tenths or more of this accumulation is so purely technical that it is dull, dismal, and worthless to the general reader. He therefore requires the help of a judicious Mentor, who shall select from the heap the most interesting morsels, and render them easily intelligible. These notes are intended to supply this demand. They will not be paragraphs produced merely by the aid of scissors and paste ; but short, simple essays carefully prepared for the Gentleman's Magasine by a writer whose long experience as a popular-science teacher enables him to form a fair estimate of popular requirements, and has trained him in the art of intelligible exposition.

The primary characteristic of natural truth, i.e. pure science, when fully understood, is simplicity, though the struggles in search of it by its discoverers may be extremely complex and difficult. An example or two will illustrate this.

Two great mathematicians, Adams and Leverrier, struggled long and arduously with the difficulties of most complex calculations in order to determine the cause of certain deviations of the planet Uranus from the path it ought theoretically to have followed. They finally determined that these irregularities are due to the gravitation of another world beyond : they told the owners of suitable telescopes where to find it, and it was found accordingly. Thus the discovery of the planet Neptune demanded a vast amount of technical mathematical skill; but, when discovered, the great fact became clearly open to all.

The Astronomer Royal and his assistants have been working for some years past in reducing the costly and difficult observations of the last transit of Venus. None but highly-trained mathematicians can accompany or follow them in this work; but its result, the distance of the earth from the sun, is intelligible to any schoolboy when fairly established and plainly stated.

The making of a railway is a very tedious and costly task ; but the travelling over it a swift and cheap one. It is the same with the truths of science. The exclusive pedant would drag you through his details of discovery and demonstration, pretending that you cannot be a passenger in the triumphal car of science without being also an engineer.

These notes are intended to carry ordinary passengers along the path of scientific discovery without requiring them to excavate their own tunnels or drive the engine.

A selection of subjects will be carefully made month by month, and only those of general interest will be treated : others that are specially technical, or interesting only to a small section of experts, will not be touched at all.

Where preliminary explanation is necessary, it will be given in as few words as may be consistent with clear and readable exposition.

A New DEVELOPMENT OF PHOTOGRAPHY.

M.

JANSSEN has announced a very curious, and at present

a mysterious, discovery in photography. He has lately produced some magnificent photographs of the face of the sun, displaying the spots, the faculæ, the “mottling" or "rice grains," or “willow leaves," as they have been fancifully called, and the other details of solar physiognomy, in a manner that affords to all and sundry fair opportunity of studying these stupendous irregularities. In the further prosecution of this admirable work, M. Janssen found that prolonged exposure destroys the picture, nothing appearing on applying the developer. Careful observation showed that this disappearance was gradual, as might be expected. So far there is no particular novelty in the observations, but by continuing the exposure beyond the period of disappearance an unexpected transformation is displayed. Instead of an ordinary negative picture with lights represented by shades, and the shades by light, a positive picture is now displayed on developinent; the bright body of the sun shown white and the spots black, as to ordinary vision. With careful manipulation this direct positive has all the distinctness of a fine photographic picture. About Toto of a second was the time allowed for an ordinary picture of the sun, and with the gelatinobromide process it of this time is sufficient. The direct positives

were obtained by continuing the exposure from half a second to a second.

What is the chemistry of this second action ? To answer this question satisfactorily, further, and probably rather extensive, investigation is demanded ; a research that must include the whole philosophy of the wondrous phenomenon of photographic development.

If among my readers there are any who have not witnessed this magical process, he or she should visit a communicative photographer, and ask for an introduction to his darkened chamber, where a glass plate, presenting only a surface of dirty-looking collodion film, is subjected to an incantation by enchanted waters, and forthwith appears a spectral image of the observer or any other person or thing the operating wizard has chosen to call forth. Nothing narrated in the chronicles of witchcraft is more weird and wonderful than this.

ARCTIC BALLOONING.

THE

'HE Central Arctic Committee, after careful consideration and

some discussion, passed unanimously the following resolution: "That, in the opinion of this committee, the plan of using three connected balloons, as tested at the Alexandra Palace, does not warrant the committee in following out further that suggestion, but leads them to revert to the original idea of using single balloons as auxiliary to the work of the new expedition.”

It is quite evident, from the valuable practical instruction derived from the rude experiment to which allusion is made in the above, that more experiments are required. The Government had done something in the study of military ballooning, but not nearly enough. Though somewhat blasé in reference to the putting forth of original projects, I am sorely tempted to revive one of the devices of my youth, suggested in the course of some struggles over Alpine glaciers, especially that of the Bossons. It was to attach to the upper part of the back, by a system of shoulder straps, a small balloon capable of lifting one's knapsack and from a half to three-fourths of the weight of the body; and thus, relieved of so much encumbrance, to skip merrily over the Alps, especially up the snow slopes and glaciers

, tripping lightly from ridge to ridge of the craggy glacier ice, and crossing its blue crevasses by easy flying leaps.

Such an arrangement, carrying a fortnight's supply of food in addition, might enable an exploring party to approach the Pole in spite of the so-called "paleocrystic ice,” provided the gas would not ooze through the balloon faster than it became relieved of ballast by

NO. 1797

VOL, CCXLVII.

B B

the consumption of the provisions. A gale of wind might possibly be inconvenient ; while, on the other hand, a favourable breeze, rather stiff, would be equivalent to the "seven-league boots" of the nursery hero. The rate of progress, in any case, should be very different from the one mile per day of Markham's sledge parties.

M.

A STEAM-ENGINE WORKED BY THE SUN. MOUCHOT, of Algiers, has fully carried into practical

effect an oft-repeated philosophical dream, viz. that of using the sun's rays directly as a source of mechanical power. I say "directly," because, as is now pretty generally understood, the combustion of coal, wood, &c. is but an indirect application of ancient bottled sunbeams to modern use.

M. Mouchot's engine has been long at work. In November last his solar furnace raised above 75 gallons of cold water to the boiling point in 80 minutes, and at the end of another hour and a half raised its steam to a pressure of eight atmospheres. On December 24 he distilled 5 gallons of wine in 85 minutes. Since the spring of last year he has been working a horizontal engine at the rate of 120 revolutions per minute, with a pressure of 31 atmospheres, pumping 250 gallons of water per hour, at 4-feet pressure. This was done from 8 A.M. to 4 P.M. without sensible hindrance by passing clouds. He has also sublimed sulphur, distilled sulphuric acid, purified linseed oil, concentrated syrups, carbonised wood in closed vessels, fused and calcined alum, &c.

The solar heat is concentrated by means of mirrors, and the boiler is enclosed in glass through which the solar rays pass readily for heating the water, while the radiations of the obscure heat from the boiler itself are obstructed by the glass. This difference of the penetrability of glass by rays of differing intensity may be easily proved by holding a piece of glass between the sun and one's face, and then repeating the experiment before a domestic fire. The glass is no screen to the solar rays, but an effective one to those from the fire. Greenhouses and cucumber-frames are heated thus. The solar heat freely enters these glass traps, but cannot readily get out again.

It should be noted that M. Mouchot's success in Algiers by no means proves that his engine would work in England. We are still likely to remain dependent on our underground fossil sunbeams, but for the inhabitants of tropical countries M. Mouchot's invention pens out quite a new era of physical civilisation.

« AnkstesnisTęsti »