B

y the time the present number of SELF CULTURE reaches the hand of the reader, it will doubtless be known what success has attended the expedition to British India, sent out from England by a joint committee of the Royal and Astronomical Societies, to report upon the total Eclipse of the Sun, which is to take place on the 22nd of January. Apropos of the occasion, Sir Norman Lockyer, professor of astronomical physics at the Royal College of Science, London, and the learned author of many valuable treatises on astronomy, has issued a timely volume dealing with "Recent and Coming Eclipses" (London and New York: Macmillan and Co.). The work chiefly consists of notes on the total solar eclipses of 1893, and 1896, with hints to govern the expedition now on its way to India. An interesting account of the volume recently appeared in the London "Spectator," from which we make the following extracts.

Sir Norman Lockyer, says the reviewer, is not only an eminently practical but a thoroughly practiced astronomer; yet he is happily one of those scientific men who do not regard as mere sentimentality the emotions that are encouraged, if not evoked, by the familiar mystery of Nature. The book which he has published is composed mainly of the actual observations of astronomical phenomena, but the making of these has not expelled from his mind what the late Laureate would have termed his "cosmic pantheism,”—that feeling which perhaps finds most adequate expression in the divine simplicity of "The heavens declare the glory of God." He opens his first chapter which bears. the title of "Eclipse Revelations and their Uses," with these words: "There is no question that a total eclipse of our central luminary is one of the grandest and most awe-inspiring sights that it is given to man to witness; feelings of awe, mingled with wonder, are at once appealed to by the attendant phenomena; and it is not surprising that in ancient times, when knowledge was less, and less widely

spread than it is now, superstition, fear, and dread put all other emotions in the shade." And so impressed has he been by the awe-inspiring experience of six eclipses, that the utmost he can do — and he could not have done better-is to quote Professor Grant's quite genuine, if slightly old-fashioned, eloquence on the subject of an eclipse written forty years ago:

"On no other occasion does the display of stupendous power in the economy of the physical universe exercise so subduing an influence over the mind, or produce so humiliating a conviction of the impotence of all human efforts to control the immutable laws of Nature and arrest the course of events, as when the

glorious orb of day, while riding in the heavens with unclouded splendor, begins to melt away from an unseen cause, and soon totally disappears, leaving the whole visible world wrapped in the sable gloom of nocturnal darkness. The scene is rendered still more impressive by the circumstances accompanying so remarkable an occurrence. The heavens assume an unnatural aspect which excites a feeling of horror in the spectator; a livid hue is diffused over all terrestrial objects; plants close up their leaves as on the approach of night; the fowls betake themselves to their resting-places; the warbling of the grove is hushed in profound silence; in other words, universal Nature seems to relax her energies, as if the pulse which stimulated her mighty movements had all at once stood still."

Yet, although Sir Norman Lockyer professes to be unable to describe his own feelings better than by quoting Professor Grant's words, he thus himself breaks out when describing the eclipse of 1871:

"There in the leaden-colored, utterly cloudless sky shone out the eclipsed sun-a worthy sight for gods and men. There, rigid in the heavens, was what struck everybody as a decoration-one that Emperors might fight for, a thousand times more brilliant even than the Star of India, where we then were! A picture of surpassing loveliness, and giving one the idea of serenity among all the activity that was going on below; shining with a sheen as of silver."

As has been hinted, this book is eminently "practical." For one thing, it gives in detail the elaborate preparations made, with, however, but imperfect success, for observing in Norway the great eclipse of August 9, 1896. For another, it explains at great length the achievements in the way of eclipse observation that have been attained by means

of the prismatic camera and the spectroscope. It is four years since the largescale prismatic camera was introduced:

"The results obtained by large-scale prismatic cameras showed everybody that these instruments were the most important ones we can employ on an eclipsed sun. They not only give us a complete chemical record on a scale hitherto undreamt of, but they give us the positions and forms of the prominences far better than these have ever been obtained before. Nor is this all; they enable us to study under new conditions some of the conclusions arrived at in previous eclipses, and give us a means of inquiring into the possible origin of some of the phenomena already recorded by slit spectroscopes."

Again, "the results obtained in that year (1893) represent, therefore, only the experimental stage; at the critical moments of the eclipse-that is, at the beginning and end of totality-only snap-shots were taken. In 1896 what is termed a dropping-plate was introduced in the programme of the prismatic camera, a plate being exposed, while gradually falling, from ten seconds before the end of totality to fifteen seconds after, in the hope of catching the so-called 'flash,' which is supposed to represent the 'reversing layer,' which 'flash,' of course, is simply the spectrum of the chromosphere. It may seem to the ordinary and essentially unscientific reader that Sir Norman Lockyer devotes too much of his comparatively limited space to the prismatic camera. But it should be remembered that, unaffected by the defeat of 1896, he is looking forward to a possible success in India on January 22nd of this year. Whether that success, from being a possibility, will become a reality, must depend not a little on the further improvement of the machinery and processes upon which Sir Norman lays stress.

thereby an additional proof of the advantage to us of the short nights. There is no time either for any considerable reduction of temperature or for the accumulation of any great amount of moisture in the air. I am glad to say

that the last adjustments have been made, the last demonstrations given; numerous rehearsals have landed us in the perfection of drill; the parties all know their stations and all necessary forms have been written out. We are going then to-day to 'stand easy,' and take some rest in preparation for the fateful to-morrow.”

The portion of Sir Norman Lockyer's book in which the failure of the expedition of 1896 is described is, nevertheless, very interesting for the amount of enthusiasm in the scientific venture which seems to have been aroused by it in the breasts of Captain King Hall and the officers and men of the 'Volage.' When the Captain condoled with the leader of the expedition on his failure in attaining his main object, the latter replied that a most important discovery had been made, that, "he had demonstrated that with the minimum of help, and that chiefly in the matter of instruments, such a skilled and enthusiastic ship's company as his could be formed in a week into one of the most tremendous engines of astronomical research that the world has ever seen; so that if the elements had been kind all previous records of work at one station would have been beaten." When Sir Norman asked for volunteers to help him and his scientific associates in their work, as many as seventy of the men of the 'Volage' came forward, and they proved not only so willing, but so capable, that he entrusted to one of the bands into which the seventy were divided the charge of a very delicate in- . strument. His experiences, indeed, seem to suggest the desirability of our finding new fields for the energies of sailors, as well as of soldiers, in times of peace.

As it is our chief purpose to point out the more popular features in this book, we merely commend to the attention of the specially interested Sir Norman Lockyer's chapters on "The Chemistry of the Sun as Determined in 1893 and 1896," "The Spectrum of the Corona," and "The Structure of the Sun's Atmosphere." The two final chapters deal with "The Approaching Total Eclipse in India" and "The Work to be Done During the Indian Eclipse." It is satisfactory to note that in the meantime all promises well for the eclipse of January 22, 1898. Sir Norman Lockyer, who

Mr.

evidently bases quite reasonable hopes on a note drawn up on the climatic and other conditions of Northern and Central India and the Deccan, in which the eclipse will be observed, comes to the conclusion that light northeast winds, fine weather, and smooth seas are to be expected. Eliot, Meteorological Reporter to the Government of India, says positively: "The weather is throughout the month of January almost uniformly fine, with clear or lightly clouded skies over the whole of the peninsula. Light northLight northeasterly to easterly winds obtain in the Deccan or interior of the peninsula. The West Coast districts are protected by the West Ghats from these winds, and light land and sea breezes prevail."

The Asiatic Society of Bengal has done a good deal in the way of collecting and disseminating information for the guidance of those visiting India on the occasion; "and be it not forgotten," says Sir Norman, almost with the air of a

tour-conductor, "that India in the cool season is reached over tranquil seas, and presents one of the finest climates in the world, to say nothing of what Nature provides in the way of tropical scenery, and successive dynasties have left behind them in the way of monuments, which are among the wonders and delights of the world." The Joint Committee of the Royal and Astronomical Societies have since the publication of this book revised certain of the arrangements they originally made, and it is to be hoped that neither pestilence nor "scare" will upset them. Sir Norman Lockyer recalls the success of the observations conducted in 1871 in India, and anticipates greater success in January 1898 because, among other reasons, eye observations have now been almost entirely superseded by permanent photographic records. Sir Norman concludes a most interesting and valuable book with a chapter for scientific experts on "The Work to be Done."

I have been interested in the " correspondent's question," on page 285 of your December number, concerning the action of a cannon ball dropped from the surface of the earth, the latter being supposed to be permeable. While your answer is correct if the ball were dropped from either pole of the earth, it would hardly be so if it were dropped from any other point. If, for instance, it were dropped from any point upon the equator, it would have an easterly velocity of over 1,000 miles per hour before it started to fall, due to the earth's rotation. At the surface of the earth it would make one revolution per day; but as its linear velocity due to its original motion would be constant, the number of revolutions which it would make per day would be inversely proportional to its distance from the earth's centre, i.e., when it was 2,000 miles from the earth's centre it would make two revolutions per day, and when it was 1,000 miles from the earth's centre it would make four revolutions per day. This does not consider its velocity due to gravity.

The linear velocity of the ball would increase as it neared the centre, due to the action of gravity. The centrifugal force of the ball, tending to throw it away from the centre of its rotation at any instant, would increase as the square of its velocity divided by its distance from the instantaneous centre of its curved path. As the centripetal force of gravity would decrease as the ball neared the earth's centre, it is plain that a point would be eventually reached at which the two forces balance, and the ball would cease to move towards the earth's centre.

Tracing the path of the ball, we find that as it starts to fall the velocity due to gravity will

be zero and its easterly velocity will be 1,000 + miles per hour. It will, therefore, for a very small time, travel nearly parallel to the earth's surface (though it would appear to fall straight down, because the earth's surface is also travelling); its velocity due to gravity will gradually increase, while the force due to gravity will decrease, the centrifugal force of the ball itself increasing, until, as explained above, the two latter forces balance each other and the ball ceases to move towards the centre. The velocity due to gravity will now decrease; its original velocity will change its direction in space, though its easterly direction, relative to the earth, will not change, and the ball will be moving away from the earth's centre.

It will reach the surface of the earth nearly opposite its starting-point, the time of its travel being the same as if it had fallen straight through. I say "nearly," because while it was travelling from one point on the surface to the other, the surface of the earth itself would have moved 700 miles to the east, and the ball would therefore be 700 miles west of an opposite point. The ball would then start in a curved path towards a point 1,400 miles west of its original starting-place and would pass on the opposite side of the earth's centre from its first path.

The sum of these rather complex motions is that the ball would describe a set of elliptical spirals, on a plane cut through the earth at the equator, the axis of which would make one revolution every twenty-four hours. If the path were not relative to the earth, but were an absolute path in space, it would be but a single ellipse which would be closed, and the earth would make its ordinary daily revolution, relative to this ellipse, as it is also relative to absolute space.

With this latter modification, and one due to the fact that gravity varies inversely as the square of the distance between the centres of the two bodies concerned, instead of directly as that distance, as in the case just considered, the phenomenon, barring air resistance, would be exactly the same as is exhibited when a comet, with an original velocity not directly towards the sun, comes into the solar system.

As we have seen, it would approach the sun until the centrifugal force equalled the centripetal force, when it would commence to move away from it, in a path either elliptical or parabolic. It is this same balancing of forces that keeps the earth in its elliptical path, and prevents it from falling into the sun. The law is the one expounded by Newton in proof of his hypothesis of universal gravitation.

I will say, in closing, that I look forward with pleasure to every number of SELF CULTURE, and consider every number a part of my education. By educated people, on all sides, I hear it spoken of in the highest terms. Personally, I simply could not get along without it.

Incidentally, mention was made of the effect of striking a swinging pendulum, when at the end of its swing, in a direction perpendicular to the plane of its oscillation, namely, the giving of it an elliptical movement. Let our imaginary cannon ball, instead of dropping from a state of rest, have at the start an eastward movement of five miles a second, and it will go round the earth, instead of through it, moving in a circle. Let its initial velocity toward the east be 1,000 miles an hour-five-eighteenths of a mile a second- and it will move in an ellipse, the longer axis of which will be the earth's diameter, or 8,000 miles; the shorter, one-eighteenth of this distance, or 444 miles, about. This would be the case in Mr. Taylor's problem of a "per

As Mr. Taylor has

BROOKLYN, N. Y., Dec. 18.

The writer of the above letter is right as to what would happen to a cannon ball dropped from the surface of the earth "the latter being supposed to be permeable" to offer no resistance to the movement of the ball. But this was not the supposition made in the question which SELF CULTURE answered. Clearly a ball could not move in the manner described by Mr. Taylor, were it confined within the limits of a "hole passing through the earth's centre." Actually a ball dropped into a very deep perpendicular hole in the earth would strike the eastern side at no very great depth, would glance to the western side, then to the eastern, and so on, as it descended more and more rapidly, and the consequent friction would be one source of the resistance it would encounter in its fall, another source being the atmosphere. If the hole passed clean through the earth, the result would be as SELF CULTURE stated; the ball-or its fragments—would finally, after repeated oscillations to and fro past the earth's centre, come to rest at that point.

In answering the question an imaginary case was considered, in which there was no resistance, the body being supposed to start from a state of rest and to be acted upon only by gravity, the effect of gravity being, obviously, the matter about which the questioner was in doubt. The answer given that the ball would under these circumstances move essentially as a swinging pendulum, was correct.

said, the axis of the ellipse would have a fixed direction in space, while the earth would rotate with reference to it. Mr. Taylor is in error upon one point, however. The movement of the ball would not be analogous to that of a comet or of any other celestial body. In celestial mechanics the attracting force varies inversely as the square of the distance from its centre varies, and this centre is always found at one focus of the orbit of the moving body. In the case above supposed, the attracting force varies directly as the distance of the moving body from the point of attraction, and this point becomes the centre — not one focus of the ellipse which the body describes.

GEO. SENECA JONES.

The discovery of a large bed of strontium at Put-in-Bay Island, reported from Toledo, has awakened a considerable amount of interest among the manufacturers of fireworks, as it is thought likely that it will result in a considerable reduction in the price of all fireworks in which strontium nitrate or strontium carbonate

is used. One large manufacturer of fireworks in New York, who makes use of about one hundred and fifty tons of strontium nitrate in a year and imports the whole of it from Europe, states that it costs his firm now about seven and a quarter cents a pound. If the strontium should be found in large quantities, it would have the effect of lowering the cost of certain classes of fireworks, that is, all those that use a red or crimson light. At present the supply comes chiefly from Germany, and the American manufacturer has to pay a high price for it.

QUESTION DEPARTMENT

Feb. 1. Give a list of the British Colonies and foreign possessions throughout the world, describing the situation of each.

Feb. 2. Indicate the chief trade routes between Great Britain and her colonies, naming the principal ports of these colonies.

Feb. 3. Name ten of the more important fortified naval depots of Britain in foreign waters, and indicate their situations.

Feb. 4. State how England came to acquire her possessions in the Mediterranean and the Levant.

Feb. 5. Name the principal British Islands in the West Indies, and state when and under what circumstances they were acquired.

Feb. 6. Trace the progress of British conquest in India from Clive's day to the close of the eighteenth century.

Feb. 7. Name the causes which led to the British conquest of Canada, and those which led to the separation of the American Colonies.

Feb. 8. What were the grievances of the people of Canada which led to the Rebellion of 1837?

Feb. 9. Name the seven provinces that constitute, with the partially organized territories, the Dominion of Canada, and give their capitals.

Feb. 10. Give the total population of the provinces and native states of British India, and indicate, approximately, the religious persuasion (Hindus, Mohammedans, Buddhists, etc.) of the people of the Indian Empire.

Feb. II. When did China cede to England her Crown Colony of Hong Kong, and how are its affairs administered by England?

Feb. 12. How and when did Ceylon fall under British rule, and when did England proclaim a protectorate over North Borneo?

Feb. 13. Give the dates of British settlement in the various Australian Colonies, and state which is the oldest colony.

Feb. 14. When did Britain obtain, by native treaty, possession of New Zealand, and when was self-government granted to the colony?

Feb. 15. What commercial advantages has Britain gained from her recent acquisition of Upper Burma ?

Feb. 16. England owns or exercises a protectorate in equatorial and Southern Africa over an area of two and a half million square miles. Name the colonies, possessions and territories within this area; state, approximately, its extent of seaboard.

Feb. 17. Of what colonies or possessions of England are the following towns the capitals: Victoria, Fredericton, Brisbane, Hobart, Wellington, Kingston, Georgetown?

Feb. 18. What are the chief provisions of the British North America Act, and when was it enacted?

Feb. 19. Name and give the position of the chief seaports of the British Isles, and locate on a map the following towns: Canterbury, Portland, Sunderland, Roscommon, Dumbarton, Drogheda, Inverness, Brighton.

Feb. 20. What possessions did England gain by the treaty of Vienna? Give the date of the treaty.

Feb. 21. Give the date of the abolition of the slave trade in the British dominions, and name the sum granted the owners as compensation for their slaves.

Feb. 22. When was the government of India transferred to the British Crown?

Feb. 23. When was telegraphic communication between this country and England finally established?

Feb. 24. Give the dates and the assigned causes of the Abyssinian and the Ashantee wars. When did the Maori war in New Zealand close?

Feb. 25. In what year was a Roman Catholic hierarchy re-established in England? Give the date of Catholic Emancipation.

Feb. 26. When was the Oregon boundary dispute settled between this country and England?

Feb. 27. When, and for what territorial compensation, did England cede Heligoland to Germany?

Feb. 28. What did Jay's Treaty accomplish in the adjustment of differences between the United States and England?