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York County connections not confined to Earth

Kirkwood Crater on the moon. (NASA photo)
Kirkwood Crater on the moon. (NASA photo)

I have shared stories of some of the well-known persons who attended or taught at the York County Academy. They include Thaddeus Stevens, abolitionist and congressman and Samuel Bacon, charged by President Monroe with the founding of Liberia.

Fellow blogger Jim McClure has shared information on other noted YCA alumni, such as acclaimed chemist Edgar Fahs Smith.

My recent York Sunday News column below tells of still another, eminent astronomer Daniel Kirkwood.

Daniel Kirkwood (York County Heritage Trust photo)
Daniel Kirkwood (York County Heritage Trust photo)

Daniel Kirkwood reached for the stars (and planets)

He has an asteroid named for him, as well as an impact crater on the far side of the moon and an outcrop on Mars. An observatory at a major American university bears his name. During his lifetime, he was hailed at the American Kepler. Does this scholar, still recognized as an outstanding mathematician and astronomer, have York County connections?

As you might guess, he does. Daniel Kirkwood’s Scots-Irish Presbyterian grandfather Robert Kirkwood (1729-1810) crossed the Atlantic in the early 1730s at the age of three. When his widowed mother remarried, Robert and his sister Isabel went to live with their uncle Robert in the Madonna area of Harford County, Maryland, just a few miles south of the Pennsylvania line. Robert Kirkwood’s son John (1763-1822) was the father of astronomer Daniel Kirkwood (1814-1895).

Many Kirkwood relatives lived in southeastern York County. At least one Kirkwood served in the York County Militia during the Revolutionary War, three Kirkwoods are named on the 1783 tax lists and Daniel’s aunt Sarah Kirkwood Anderson resided in the Cross Roads area. His main York County ties have to do, however, with the education and teaching experience he obtained here, leading to the path he followed through life.

His biographers state that he left the family farm in 1833 at age 19, moving north of Mason and Dixon’s line to teach at a country school in Hopewell Township. The story goes that one of his students wanted to learn algebra. Kirkwood also wanted to know more, so they borrowed a copy of Bonnycastle’s 1782 Introduction to Algebra and learned together. Wanting more education for himself, Kirkwood enrolled at the York County Academy in 1834 where he studied mathematics. Upon finishing his studies in 1838, he was appointed instructor in mathematics and natural philosophy (what we call science).

In an original 1838 letter, now in the York County Heritage Trust archives, Daniel wrote to his cousin Nathaniel Kirkwood: “I expect to continue in York for some time—perhaps several years…,The trustees have had a meeting and their committee, Doct. McIlvaine and Hon. Chas. A. Barnitz have been down to inform me that they have appointed me teacher…They give me three hundred dollars a year…and say they expect to continue. This is much better than teaching a country school, and besides I have the advantage of pursuing my study of Latin. (Three hundred 1838 dollars would be about $7,500 today.)

He did stay at the York County Academy for five years, leaving in 1843 to become principal of Lancaster High School. He married his wife, Sarah McNair, while serving in Lancaster, and then moved to Pottsville in 1848 to be principal at Pottsville Academy. Kirkwood continued in higher education as Professor of Mathematics at Delaware College (now the University of Delaware) in 1852. In 1856 he accepted an offer to become Professor of Mathematics at Indiana University. The Kirkwoods spent most of the next 30 years at Bloomington, until his retirement in 1886, by which time he was widely celebrated for his astronomical work.

What did Kirkwood accomplish in his studies to be so universally esteemed? Much of the respect he received is the result of his pioneering studies of asteroids, minor planets, comets and meteors. Kirkwood’s first two books, Meteoric Astronomy (1867) and Comets and Meteors (1873), quickly became well known. He was the first to theorize and produce convincing evidence that periodic meteor showers are the debris of long disintegrated comets.

His most important work is said to be the discovery of gaps clear of usual debris, now known as Kirkwood Gaps, in the orbits of asteroids or minor planets. The asteroid belt orbits the sun between Mars and Jupiter. Kirkwood theorized that the gravitational pull of Jupiter caused the gaps. That initial work was done in the late 1850s and 1860s, making the discovery even more remarkable, since there were only about 50 asteroids known then. With advances in astronomy and telescopes, tens of thousands of asteroids have been documented since, ranging in size from pebbles to the largest known asteroid, Ceres, which is about 600 miles in diameter. Subsequent discoveries in the asteroid belt have verified Kirkwood’s theory.

Besides his research and writing, Kirkwood spent time teaching and was held in high regard by his students. One of his students is said to have stated that when he died he wanted to go wherever Dr. Kirkwood went. While some seemed to see science as a threat to religious beliefs, Presbyterian Kirkwood was quick to attest that his study of the stars strengthened his faith.

Retirement from Indiana was not the end of Kirkwood’s academic career. The Kirkwoods’ only child Agnes was an invalid who died at 28 in 1874. Upon retirement Daniel and Sarah went to southern California to live with a nephew on his orange ranch. Because of his esteem, in 1891, at age 77, he became a Lecturer of Astronomy at Stanford University, founded only a few years before. A prolific writer in his field, Kirkwood published around 125 papers and three books during his lifetime, his last book, The Asteroids or Minor Planets between Mars and Jupiter, after retirement. He is buried in Bloomington, Indiana with his wife and daughter. Obituaries in astronomy journals described Kirkwood as having a “kindly, upright, beautiful character, a true and good man.”

He was so esteemed in Bloomington that all businesses closed in the city on the day of his funeral. Bloomington boasts a Kirkwood Avenue, and Kirkwood Observatory and Kirkwood Hall on the Indiana University campus are both named for him. Kirkwood has been highly honored by the astronomical community, with Asteroid 1578 Kirkwood carrying his name, along with the Kirkwood impact crater on the far side of the moon and an outcrop called Kirkwood on Mars.

Since my astronomical expertise consists of picking out the big dipper on a starry night, I have focused more on Kirkwood’s area connections instead of his stellar accomplishments. Much more on Kirkwood’s work can be found in books and online.

Another view of the Kirkwood moon crater. (NASA photo)
Another view of the Kirkwood moon crater. (NASA photo)