Centennial for A Spectrometer
ONE hundred years ago, in February 1866, Charles Augustus Young, 1853, returned to Dartmouth as Appleton Professor of Natural Philosophy and Professor of Astronomy. In this position he was to establish himself as a renowned physicist-astronomer.
Soon after his arrival in Hanover, and after corresponding with Professor Cooke of Harvard, he ordered a high-dispersion spectrometer, similar to one used by Sir Norman Lockyer, from Alvan Clark and Son, the famous telescope makers, at a cost of $350. This instrument, with its train of six 45° prisms, had been designed specifically for studying the detailed structure of the solar spectrum; but with many modifications and added parts, in succeeding years it served in other ways for both research and teaching. Finally, in 1963, after nearly 100 years this venerable instrument was retired from active service and placed in a display case in Wilder Hall.
This month, at the 50th anniversary meetings of the Optical Society of America being held in Washington, D. C., March 15-18, Professor Young's spectrometer will be part of an exhibition devoted to highlights in the field of optics during the past century.
Reassembling the original Young multiprism spectrometer in 1963 was like tackling a three-dimensional jig-saw puzzle. Parts had been removed and had become scattered. Fortunately, Young had described the telescope and collimator in an early paper, and a few years later the complete instrument had been photographed among the collection of philosophical apparatus at the College. Under the direction of Prof. Allen L. King of the Physics Department, the reassembly was successfully managed, but a few parts are still missing.
The Young spectrometer figured importantly in achievements of the 1869 solar eclipse expedition to Burlington, lowa. In preparation for the observations there Professor Young constructed a "telespectroscope" from the telescope and collimator of the spectroscope, a train of five 45° prisms, and a 4-inch "cometseeker" made by Merz and Son, all mounted on a wooden frame. With the assistance of Prof. Charles F. Emerson he observed the spectrum of the corona and identified the bright green line as belonging to the chromosphere of the sun.
Upon his return from the eclipse expedition Young commissioned the building of a new form of spectroscope with double the dispersion of the multiprism spectrometer. With this instrument Young in 1870 observed the structure of solar prominences, sunspots, and flares, and he measured the speeds of moving plasma clouds and escaping gases. Then it was shipped to Jerez, Spain, for observing the December 1870 solar eclipse. It was at Jerez that Young saw the flash spectrum for the first time and discovered the reversing layer of the sun. The optical system was so well aligned and the telescope so carefully set on the limb of the sun that "as the crescent grew narrower ... the dark lines of the spectrum, and the spectrum itself, gradually faded away, until all at once, as suddenly as a bursting rocket shoots out stars, the whole field of view was filled with bright lines more numerous than one could count."
Young's "new spectroscope," a spectrohelioscope, was found dirty and dusty but intact in a small storage closet in Dartmouth's Shattuck Observatory.
Prof. Allen L. King with the spectrometer, now displayed in Wilder Hall, 100 yearsafter it was built for Dartmouth's famed physicist-astronomer, Charles A. Young.
Headliners at the football banquet last month included (l to r) All-American centerDon McKinnon '63, President Dickey, Captain Nate Parker "26 of the 1925 undefeated team, and Tom Clarke '66, captain of last fall's undefeated team, Ivy Leaguechampion and Lambert Trophy winner. The Cornell game ball in the foregroundwent to guard Tony Yezer '66, who received the Manners Makyth Man Award andan NCAA graduate scholarship as an outstanding scholar-athlete.
