WHEN we trace back the chain of causes which led to the construction of the great Washington telescope, we find it to commence with so small a matter as the accidental breaking of a dinner bell in the year 1843 at the Phillips Academy, Andover, Massachusetts. One of the scholars of the Academy, George B. Clark by name, gathered up the fragments of the bell, took them to his home in Cambridgeport, put them into a crucible with some tin, and proceeded to melt them in the kitchen fire. His mother very naturally inquired the cause of such an interference with the culinary arrangements, to which he replied that he was going to make a telescope. Having melted his metals, he cast them into a disc, and commenced grinding them into a slightly concave mirror. His father learning what he was doing, lent a helping hand, and the combined skill of father and son was soon rewarded by the completion of a five-inch reflecting telescope which would show the satellites of Jupiter, the rings of Saturn, and other telescopic objects.

Such was the origin of the now wellknown firm of Alvan Clark & Sons. The father was then a portrait painter in Cambridgeport, and within the limited circle of his acquaintance the accuracy of his portraits and the patience which he devoted to their finish, brought his work into high esteem. He was entirely self-made, having received no higher education than that afforded by the district school of his native place, or by his own reading; but this defect was more than compensated by his natural genius, which was of a much higher order than that of the so-called practical man. It is interesting to notice the early development of those qualities he has since exhibited in the construction of telescopes. At the time of which we speak he was much more widely known as a champion shooter with rifles of his own make than he was as a portrait painter. His success in this apparently unartistic and unscientific pursuit was due to the extreme accuracy with which he cut the bores of his weapons, and figured his balls, and to the precision of his eye-sight.

He now entered with ardor upon the path so curiously opened up by the experiment of his son. He made reflectors of larger size, and began to employ them in scanning the heavens. Among other objects he examined was the great Nebula

of Orion, that celestial mystery which nearly every great telescope of the world has sought to unravel. He confined himself to making a little map of all the small stars he could see in the nebula, and when it was done he exhibited it to Professor Bond, the director of the newly-founded observatory at Cambridge. Surprise was expressed at the number of minute stars Mr. Clark could see with so small an instrument, and the astronomer remarked one in particular which Herschel had not seen with his twenty-foot reflector.

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Mr. Clark now began to consider the feasibility of grinding the glasses of a refracting telescope, and suggested the project to his son. 'Ah, father, we cannot do it," replied the learned boy. "All the writers say that figuring a lens is an operation of extreme difficulty." But the father was not a man to be stopped by any dictum of so vague a body as that of " writers," and he resolved to make the attempt. A pair of four-inch discs of optical glass were procured, and, after considerable labor, he produced an object glass which seemed. to him perfect. He now went to Professor Bond and told him that he had a four-inch glass which he proposed to try alongside of a Munich glass, which Bond considered one of the finest he had ever seen. proposal was accepted, and the new glass was brought to the observatory, mounted in a wooden tube. Pointing it at a bright star the practiced eye of the astronomer soon detected what seemed to be a very serious defect. The glass did not show the star in its proper shape as a simple lucid point, but added a little tail like that of a minute comet, which seemed to extend upwards from the star. Mr. Clark looked. There was the tail sure enough. Yet he was quite sure the glass had never before shown such an appendage, and that it was not due to any defect in the instrument itself. But he was quite unable to explain it, and the glass was in consequence pronounced a failure.

After considerable thought and experiment the cause of the difficulty was divined. The wooden tube under the cold sky radiated heat from its upper surface, and was warmed by the heat from the ground on its under surface. The result was that inside of the tube was a very thin layer of warm air at the bottom, and an equally thin layer of cold air on top. The tube

was scarcely larger on the inside than the aperture of the object glass. The consequence was that much of the light which traversed the extreme edge of the glass was refracted upwards by these layers of air through which it had to pass, and formed the tail to the star. Mr. Clark found that he could avoid the difficulty by making the tube at least half an inch larger than the glass, and wrapping tin-foil around it when he used it under the open sky. The small radiating power of the tin-foil prevents its cooling so rapidly by radiation to the sky, while it reflects most of the heat which comes from the ground, and thus preserves more equable temperature than the naked wood.

During several years Mr. Clark devoted his leisure to the making of glasses of gradually increasing size, which he mounted in the simplest manner, and generally sold to private individuals. Some of these are still to be found in the hands of exhibitors on Boston Common. To many of our readers it may seem strange that a maker of telescopes equal to any in Europe, should have worked for ten years without receiving the slightest recognition or encouragement from any official, scientific, or educational quarter, although the time was most favorable for such recognition. The year in which he made his first telescope was marked by the projection or foundation of the Cambridge, Washington, and Cincinnati observatories, and the ten years during which he worked in entire obscurity were those of the revival, or, we might say, the foundation of practical astronomy in the United States. The case strongly illustrates the cause which more than any other now retards the progress of science in America; namely, our total indifference to genius which does not force itself into notice. Even at the present time the highest scientific ability in this country stands hardly a chance of recognition away from the great center of activity. As these lines are written, one of the first mathematicians of the century-fairly the peer of Hansen or Leverrier-has for ten years studied and worked in obscurity in a county district without receiving a fourth of the recognition, reward, or encouragement he would have received in any country of Europe.

We trust that every true lover of the intellectual progress of America will feel mortified to learn that the first scientific recognition of Mr. Clark's genius in the diffi

cult art he has pursued with such success, came from Europe. The Rev. W. R. Dawes of England, was, at the time referred to, one of the leading amateur astronomers in England, and was celebrated for his performances in the measurement of double stars. He was among the finest and most critical judges of telescopes living, while his personal character and virtues corresponded to his intellect. To him Mr. Clark ventured to write without any introduction, describing his efforts in the construction of telescopes, and stating what he had been able to do in resolving the very difficult triple star of Andromeda. This letter opened a correspondence which lasted as long as Mr. Dawes lived. The latter began by sending Mr. Clark a list of certain difficult celestial objects which he wished him to examine and describe. This was done in a manner so satisfactory to Mr. Dawes, that he made a proposal to purchase Mr. Clark's glass, which the latter accepted, and the glass was sent over to England in the Autumn of 1853. Its performance was so satisfactory that Mr. Dawes soon ordered a second. The reason for sending these orders to America was that there was not, at that time, an establishment in England which could grind a large object glass into accurate shape, so that English astronomers were in this respect entirely dependent upon the two or three German houses who possessed the art. When a thirteen-inch telescope was constructed for the Royal Observatory, Greenwich, it was found necessary to send to Munich for the object glass.

Although England had lost the art of shaping object glasses, the yet more difficult art of casting rough glass of the necessary purity and uniformity was brought to the highest perfection by an English firm, of which we shall have further occasion to speak. Mr. Clark was therefore obliged to import his rough discs to fill the orders of Mr. Dawes. Here he met with a serious obstacle from a piece of machinery operated by the Government for the nominal purpose of "protecting domestic industry," but the real effect of which is to obstruct the higher forms of industry by increasing the cost of all the appliances necessary to their successful prosecution. The Custom-House no sooner found Mr. Clark importing unheard-of lumps of glass of great value than it set upon him as if he were a public enemy. Optical glass not being then recognized in

the tariff, the discs were classified as cut glass, owing to one or two square inches on the edge having been polished to test them; and the enormous duty of 30 per cent. was levied upon them. What was still worse, the duty was based not on the actual value of the discs as optical glass, but upon the guarantee value, which included the large additional sum paid to the founder in consideration of guaranteeing that if the glass did not prove good, new discs would be furnished. Applying to the Collector to know whether he could not secure a drawback upon the duties in consideration of the article being designed for re-exportation, he was humorously informed that if he would pay for the services of a watchman to keep control of the glass during the whole period of the manufacture, so that the watchman could swear that the glass exported was the identical one on which the duty had been paid, a drawback would be allowed. These illegal exactions of the Custom-House became so oppressive that Mr. Clark was obliged to appeal to the courts for relief. He brought suit against the Collector for duties illegally levied, and gained his case, but the costs absorbed the whole amount recovered.

The second glass ordered by Mr. Dawes was almost completed when, one day, as Mr. Clark was carrying it out to test it, it slipped from his hands and was broken to pieces. The product of many months of labor, and of no small pecuniary outlay, lay before his eyes a pile of worthless fragments. He could not even begin his work over again until he had again purchased his glass in England, and again paid the demands of the Custom-House. As soon as he could recover from the shock, he sent another order for the glass, but it was so long in being executed that he made inquiries in New York, to learn whether a pair of discs could not be procured there. In this inquiry he was successful, so that when the discs first ordered at length arrived, he had two pairs on hand. He worked the best objective he could from each pair, and sent them both to Mr. Dawes, who found so much difficulty in making a choice that he kept them both.

more or less wedded to their particular forms of machinery for working the instrument, and deviated from them with great reluctance. But Mr. Clark, not being a trained engineer, Mr. Dawes found in him one who was ready to adopt and incorporate in an instrument any feature he might desire, and who would follow his multiplicity of minute directions with the most scrupulous accuracy. When he wished to introduce improvements, his general course was not to alter the instrument he already had, but to order a new one with the improvements, and then sell the old one. With his high reputation, both as a man of character and a judge of telescopes, he never had any difficulty in disposing of such an instrument. It thus happened that up to the time of his death, in 1867, he had ordered some half dozen object glasses and several complete telescopes from Mr. Clark, which are now scattered in various hands throughout England.

During the period of these transactions with Mr. Dawes, Mr. Clark's reputation was widely extended in his own country, and he was able to turn his entire energies to his new profession with a good prospect of success. About 1859 he procured glass for the construction of the largest refracting telescope yet made. The great pair of refractors made by Merz and Mähler for the observatories at Pulkowa and Cambridge had reigned without rivals for about twenty years. The clear aperture of the object glass of each was about fifteen inches. The discs which Mr. Clark now commenced to work were large enough for a clear aperture of 181⁄2 inches, and would therefore admit about fifty per cent. more light than the instruments of Cambridge and Pulkowa, This glass was completed in 1862, and was scarcely pointed at the heavens in its temporary tube when a remarkable discovery was made with it. To comprehend the interest of this discovery, we must mention a circumstance in the recent history of astronomy.

It is perhaps half a century since Bessel found, by a comparison of Bradley's observations of Sirius, made between 1750 and 1756, with his own, that the motion of that star exhibited a remarkable peculiarity. It did not move in the heavens in a straight

stars, but varied its motion in such a way as to indicate that it was revolving around some center very near it. Bessel could not doubt that this force was due to the