52 



ASTRONOMICAL PROGRESS IN 1896. 



T. Yerkes, a wealthy citizen of Chicago. In further- 

 ance of his scheme, A Ivan G. Clark secured from 

 France 3 perfect disks of optical glass, crown and 

 flint, 40 inches in diameter, which after great labor 

 he has converted into the giant lenses. The finished 

 objective has been tested recently by an expert, Prof. 

 James E. Keeler, Director of the Allegheny Observa- 

 tory, Pennsylvania, and Prof. George E. Hale, of the 

 Yerkes Observatory. They found the definition to 

 equal that of the telescope at the Lick Observatory, 

 Mount Hamilton, California, which also is the work 

 of Mr. Clark. The light-gathering power of the two 

 objectives is as 5 to 4. The number of square 

 inches in the Lick glass is, approximately, 1,018, and 

 in the Yerkes 1,357. 



The form of the observatory is that of a Roman 

 cross, with three domes and a meridian room at the 

 end of each. The principal axis of the building 

 is 330 feet long, lying east and west. The great 

 dome, 90 feet in diameter, is at the west end. 

 This, the largest ever constructed, was designed 

 and built by Messrs. Warner and Swasey, of Cleve- 

 land, Ohio. The sole plate and ribs are of steel. 

 It is revolved by an electric motor. As the tele- 

 scope is but 75 feet in length, the dome affords 

 ample room for the spectroscope attachment and 

 for manipulation of the chair. A high chair is 

 not needed, as the floor is elevated and depressed 

 through a range of 23 feet by a special electric 

 motor. Similar motors are made to do service in 

 many ways. Of the 2 smaller ones, constructed 

 by the same firm, that to the northwest will house 

 Prof. Hale's telescope, which for several years has 

 done duty in Kenwood Observatory, Chicago, while 

 the other will contain a 24-inch reflector. Between 

 these two domes is the heliostat room, 100 feet long 

 and 12 feet wide. The heliostat, with plain mirror 

 24 inches in diameter, stands on a pier at the north 

 end of this room under an iron roof, which is rolled 

 off to the south. The main building has a hall 

 through its center, on each side of which lie the 

 necessary anterooms These rooms and those in 

 the basement are as follow : Computing room, li- 

 brary, museum, lecture room, two spectroscopic 

 laboratories, chemical laboratory, galvanometer 

 room, instrument room, photographic dark room, 

 developing room, enlarging room, emulsion room, 

 constant-temperature room, physical laboratory, 

 optician's room, and workshop. The building con- 

 taining the engines, dynamos, and boilers for the 

 generation of power and heat is several hundred 

 feet from the observatory, for avoidance of danger 

 from fire and possible boiler explosions. A novel 

 feature of this institution will be its instrument 

 shop, where, in due time, it is hoped, it will be 

 possible to construct such instruments and labora- 

 tory apparatus as shall be needed for advanced in- 

 vestigation under the immediate supervision of 

 those who are to use them. 



The site of the observatory, consisting of 50 

 acres of wooded land fronting on 'Lake Geneva, 

 is one mile from the village of William's Bay, Lake 

 Geneva. Wis., about T-") miles from Chicago, in ah 

 ideal rural region free from the dust and smoke of 

 the city, and, what is still more advantageous, away 

 from its electric street lights, which are ruinous to 

 astronomical observatories. In extent and conven- 

 ience, no observatory in the world can equal the 

 equipment of the Yerkes. Its principal instru- 

 ments will include three telescopes, the main one 

 being the greatest refractor the world has ever 

 produced, sidereal and mean-time clocks, a position 

 micrometer, a solar spectrograph, a stellar spectro- 

 graph, a photoheliograph, a transit instrument, and 

 a meridian circle. 



Its publications will consist of irregularly is- 

 sued bulletins with announcements of discoveries 



and results, contributions, annals of the observa- 

 tory in quarto-volume form, and the ''Astrophys- 

 ical Journal." Its director is Prof. George E. Hale ; 

 the astronomers, Dr. E. E. Barnard and Prof. S. W. 

 Burnharn, eminent specialists ; the astrophysicist, 

 Prof. I. L. O. Wadsworth ; while Dr. T. J. J. See 

 has the chair of Astronomy in the University of 

 Chicago, of which the Yerkes Observatory is a 

 branch. 



The construction of the objective in the mam- 

 moth telescope is similar to that of the Lick tele- 

 scope, the crown and the flint lenses being in this 

 instance separated 7 inches. Their weight, includ- 

 ing the cast-iron cell in which they are mounted, is 

 1,000 pounds. At the test of the instrument on 

 different objects in October, at Mr. Clark's optical 

 works, Cambridgeport, Mass., on four nights, good 

 images at the focus were obtained of stars at wide- 

 ly different altitudes, the definition being equal to 

 that of the Lick telescope, while the brightness of 

 the images was considerably greater. With a low 

 power the Orion nebula was a wonderful object. 

 But Prof. Keeler thinks he has evidence that we 

 are approaching the limit of size in the construc- 

 tion of great objectives. The conclusions arrived 

 at regarding this most excellent glass were shared 

 by both the astronomers testing it. Profs. Keeler 

 and Hale, the former gentleman having been a user 

 of the Lick telescope, and therefore called as an 

 expert to this trial of merit, which, by the terms of 

 the contract, was necessary to insure its acceptance 

 by the observatory. 



Comets. Since last year's report nine comets 

 have been discovered, though two were expected re- 

 turns to perihelion, and can therefore hardly be 

 called discoveries. 



Comet b 1896 (Faye's) was first detected at the 

 Nice Observatory, France, on Sept. 26. It was ex- 

 ceedingly faint and was seen at but few observa- 

 tories. Its period is nearly 7'5 years. It is never 

 visible to the naked eye, as is also the case with 

 nearly all the periodics, that belong to the Jupiter 

 family of comets. It arrived at perigee (nearest 

 the Earth) in October, 1895. but was not in peri- 

 helion (nearest the Sun) until March 19, 1896. It 

 has appeared with unfailing regularity since its 

 discovery by Faye. on Nov. 32, 1843. 



Comet a 1895 (Swift) was discovered by Dr. Lewis 

 Swift at Lowe Observatory, Echo Mountain, Califor- 

 nia, Aug. 21. 1895. It was noticed in the last volume 

 of this publication, but the elements of its orbit, 

 for lack of accurate observations and computations, 

 were given erroneously. It proves to have a short 

 period, and is with good reason thought to be iden- 

 tical with the long-lost comet of Lexcll discovered 

 by Messier, June 14, 1770, with a computed period 

 of 5 - 5 years. It must therefore have made about 

 twenty unobserved returns to perihelion. The ele- 

 ments of its orbit are often changed by near ap- 

 proaches to Jupiter, another of which will occur in 

 1922, but not to the extent of those of 1886. Based 

 on observations extending over two months, M. 

 Schulhof has computed the following elliptic ele- 

 ments : Perihelion passage, 1895, Aug. 20 - 8272, Paris 

 mean time longitude of perihelion = 338 4' 16" ; 

 longitude of node = 170 18' 8"; inclination = 3 

 15" ; eccentricity = G'65155 ; mean daily motion = 

 493'743 ' '; period = seven years one hundred and 

 eighty-six days. The computer thinks it will not 

 again be visible until its fifth return in 1931. 



Comet 1895 c (Perrine) was discovered on the 

 morning of Nov. 17 in Virgo, right ascension 13 h 

 44 : declination north 1 40'. It was visible with 

 an opera glass when discovered, and soon became 

 conspicuously visible to the naked eye. On Nov. 

 26 its tail was 5 long. The following parabolic 

 elements have been computed for it by Prof. Camp- 



