ACADEMY OF SCIENCES] BIOGRAPHY 13 



largo refractor, employing a secondary magnifying lens. It will be understood that the direct 

 images of the planets are so small, even in an instrument of long focus, that the grain of the 

 plates makes it impossible to secure a satisfactory photographic enlargement. This work 

 required great skill and patience, because, as Professor Barnard said: 2 



Better conditions are required for successful work in this direction than for visual observations. One can 

 do much visually under conditions where the best definition is only momentary, but for these enlarged photo- 

 graphs any break in the definition for even a single second during the exposure means injury or total ruin to the 

 image. In all the exposures, though of only a few seconds' duration, it was necessary to guide the telescope 

 to keep the image stationary. This was done by bisecting the polar cap by cross-wires (spider threads) in the 

 focus of the long guiding finder (61 J/o feet focus) of the 40-inch telescope. 



It was intended that a full description of this photographic work on planets should be pub- 

 lished in the Astrophysical Journal, but Professor Barnard never found time to do this. He 

 obtained also pictures of Jupiter and of Saturn, but instants of the finest seeing when such work 

 was in progress were too rare to yield entirely satisfactory pictures. When visiting Mount 

 Wilson in 1911, Mr. Barnard obtained fine photographs of Saturn with the 60-inch reflector. 



We have mentioned before that Mr. Barnard's early interest in the photography of comets 

 and their tails did not abate after the Bruce telescope was put into operation at the Yerkes 

 Observatory. He secured fine series of photographs of all that appeared in our sky, of which 

 may be particularly named: Giacobini's of 1905-6, Daniel's of 1907, Morehouse's of 1908, 

 Halley's of 1909-10, Brooks's of 1911, Delavan'sof 1914. Of these, Comet Morehouse of 1908 

 and Brooks of 1911 exhibited the most remarkable activity in their caudal demonstrations, 

 and their eccentricities kept Mr. Barnard almost constantly at the telescope while it was possi- 

 ble to photograph them. 



The return of Halley's comet was awaited with the keenest anticipation by Mr. Barnard. 

 He took many photographs of the region where it might be expected in 1909, and followed it 

 persistently after it was revealed on Prof. Max Wolf's plate of September 1 1 of that year. The 

 records of previous appearances of Halley's comet had been most carefully studied by Mr. 

 Barnard, but there were many points on which the history was silent or incomplete. He 

 determined to provide against this deficiency at the return of 1910. He kept very full notes on 

 all his observations during the 20 months through which he was able to follow the comet, and 

 embodied these in a long paper appearing in the Astrophysical Journal for June, 1914, entitled 

 " Visual observations of Halley's comet in 1910" (39:373-404). In this paper he says: 



Halley's comet at its return in 1910, though a brilliant and interesting object to the naked eye — especially 

 in the month of May — was, nevertheless, a disappointment when considered from a photographic standpoint. 

 It is safe to say that it did not give us any new information concerning these strange bodies. 



The expected passage of the tail of the comet so close to the earth as to envelop it on May 

 18-19, 1910, kept Mr. Barnard on the qui vive, and the sky was watched throughout the day 

 as well as the night with the greatest care. Mr. Barnard felt amply rewarded for his pains by 

 the spectacle of the tail in the early morning of the 19th, when he could map it visually for a 

 length of 120° ; even on the preceding morning he had been able to record its length as 107°. 

 He last saw the comet a year later, on May 23, 1911, when he secured a position of it with the 

 40-inch telescope, with some difficulty on account of its faintness. 



In order to have observations of this comet made in longitudes otherwise unoccupied, the 

 Committee on Comets of the American Astronomical Society, of which Professor Barnard was 

 an active member, secured a grant from the Bache fund of the National Academy of Sciences, 

 which made it possible to send Mr. Ferdinand Ellerman, of the Mount Wilson Observatory, 

 to photograph it at Diamond Head, Hawaii. Mr. Barnard spent considerable time in pre- 

 paring his part of the report of the committee, which was printed in the Publications of the 

 Society in 1915. 



It will be understood that in addition to his photographic observations of comets, Professor 

 Barnard was always obtaining then- positions with the filar micrometer of the 40-inch telescope, 

 whenever such positions were necessary, upon the first appearance of a comet or after it became 



» Monthly Notices of the Royal Astronomical Society, 71: 471, 1911. 



