Alvan Clark: Artist, Astronomer – Telescope Maker



The Story of His Useful and Busy Life.

How He Became an Astronomer — How His Telescopes Were Manufactured — His Honors at Home and Abroad.

Alvan Clark, whose death at Cambridge, Mass., at the age of 83, was recently recorded, did more to advance astronomical science than any other person of this century. As a telescope maker his reputation is world wide. when Dom Pedro, of Brazil, visited this country some years ago he said there were three persons in Cambridge whom he wanted much to see. These were Longfellow, Professor Agassiz and Mr. Alvan Clark.

At the age when most persons think they are too old to begin any new business or learn anything, or even go on energetically with what they do know, Mr. Clark began the work which made him famous. He did not so much as know anything about it. Nor did he ever see a lens in process of construction outside of his own shop. He lived on a farm until he was 22 years old. His early education was such as the common schools afforded. In his 23d year he went to Lowell and became a calico engraver. He had a talent for drawing which he developed unaided. For nine years Mr. Clark was a calico engraver. Meanwhile he took up portrait painting. He located in Boston and painted heads for twenty years, earning over $20,000 with his brush, without ever having been taught anything about art. Though he grew famous in quite another field, it was to his days of artist life that he always went back in memory with the most affection. And during his later years he again took up the brush and found pleasure and recreation in the work of his young manhood.

He was more than 40 when he became interested in telescopes. Assisted by his two sons he afterward produced the most accurate and the two largest instruments in the world. His oldest son, George B. Clark, while in college at Andover read a treatise on “Casting and Grinding the Speculum.” Inspired by that he conceived the idea of making a telescope. He consulted his father, who at once became deeply interested in it. They worked together at the experiment, and from this small beginning came the great work which brought them fame and wealth. Both sons were later included in the business, and the firm was known as Clark & Sons, and they worked together nearly forty years.

Grinding lenses is a work which requires the utmost nicety. Often, after months of careful labor, a flaw is found and all the work must be lost. Once when Mr. Clark was giving the final polishing to a lens upon which a year’s time had been expended, it fell to the floor and was broken. Looking woefully at the fragments a few moments in silence, he stood up saying: “Boys, we will make a better one.” The unlimited patience, which enabled him to be cheerful under such a disaster was his chief characteristic. And he was ever cheerful and companionable.

Mr. Clark was the first optician in the United States to make achromatic lenses, each completed lens being composed of two pieces, one of crown and the other of flint glass, and he invented numerous improvements in telescopes and their manufacture, including the double eye piece, an ingenious method of measuring small celestial arcs. He made the 18.5 inch glass now in the Chicago observatory; the one of 24 inches aperture for the Washington observatory, and the 30 inch refractor for the Imperial observatory of St. Petersburg, for which the honorary medal of Russia was awarded — the only one ever conferred upon an American. The last and greatest work of Mr. Clark and his sons was the construction of a 36 inch refractor for the Lick observatory on Mt. Hamilton, in California. This will be finished in a few months, and will be the largest in the world. Mr. Clark was also an astronomer of note, and made some valuable discoveries, for which the Lalande gold medal was awarded him by the French academy. The cheapest telescope Mr. Clark ever made cost $300, while the National he sold for $16,000, and the Lick glass will cost $50,000 without the mounting. The objectives alone to these instruments are worth $25,000 each, and are capable of a magnifying power of 2,000 diameters, and of increasing the surface of the object viewed to 2,500,000 times its natural size. It takes a month’s solid labor to make a good 4 inch objective, and a year for an 8 or 10 inch one.

In recognition of his great contributions to science degrees were conferred on Mr. Clark by the universities of Harvard, Amherst, Princeton and Chicago, but he had worked at telescopes for ten years without receiving the slightest recognition or encouragement from any official, scientific or educational quarter. And yet these ten years were those of the revival or foundation of practical astronomy in the United States. To Mr. Dawes, a scientific divine of Europe, is due the credit of bringing out this telescope maker. At the time Mr. Clark began a correspondence with Mr. Dawes there was not in all England an establishment which could grind a large object glass into accurate shape. England had lost the art of shaping object glasses, but rough glass of the necessary purity and uniformity was cast there as in no other country. Mr. Clark for some time imported his rough disks to fill the orders he received from Mr. Dawes, who was a telescope fancier, always on the lookout for improvements in construction and mounting.

Only the very largest lenses are ground by machinery. The tools for grinding a lens are very simple — merely round plates of cast iron, about three feet in diameter, hollowed out to suit the curves of the lens. They look like huge, shallow saucers. Three of these tools are necessary, one nearly flat for the inner surface of the flint glass, one convex, for its outer surface, and one concave, for the crown glass. The surface of the tool is covered with coarse emery and water, the glass is laid upon it, and the grinding is carried on by sliding the glass back and forth on the tool. While sliding, the glass is slowly turned around, while, at the same time, the operators continually move around in the other direction, so that the strokes are made successively in every direction on the tool. By these combined motions every inequality, either on the glass or the tool, is gradually worn away, and both are reduced to portions of nearly perfect spheres. Then finer emery is used until the surface becomes quite smooth. Then comes the polishing. The whole tool is covered with a thin coating of pitch, which is pressed, while still warm, into the proper shape. It is then covered with a layer of water and the polishing rouge, and the glass is again laid upon it, and kept in motion in the same way as in the fine grinding. Thus each surface of the two glasses is speedily brought to a high polish. Then the glass is tested to find the defects. It is set up on edge, facing a luminous point at a distance equal to ten or fifteen times the focal point. The image of the point formed in the focus of the glass is then examined with an eye piece of high power. The glass is then taken back to the tool and the polishing process is recommenced, only pressing upon those parts of the glass where it has to be ground away. It is tried again, and again goes to the polisher.

So far no extraordinary skill on the part of the workman is required; but as the size of the glass is increased the process becomes more difficult and tedious, and the difficulties of judging what the defects are increase enormously.

The telescope is by no means finished with the glass. It must be tubed properly. It must admit of being moved by clock work in such a way that as the earth revolves from west to east the telescope shall revolve from east to west with exactly the same velocity, and thus point steadily at the same star. The details of the machinery for attaining these and other results have required a large amount of thought and care.

Bismarck Daily Tribune (Bismarck, North Dakota) Sep 8, 1887

Specification forming part of Letters Patent No. 8,509, dated November 11, 1851.

To all whom it may concern:
Be it known that I, ALVAN CLARK, of Cambridge, in the county of Middlesex and State of Massachusetts, have invented a new and useful Improvement in Telescopes…

Specification of Letters Patent No. 1,565, dated April 24, 1840.

To all whom it may concern:
Be it known that I, the undersigned, ALVAN CLARK, of Cambridge, in the county of Middlesex and State of Massachusetts, artist, have invented a new and useful Improvement in Rifles, which I call a “Loading-Muzzle,” …


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