ACADEMY OP SCIENCES] BIOGRAPHY 9 



13, comparing the positions of the latter with measures obtained by Scheiner at Potsdam on 

 photographs taken in 1891. The views of astronomers as to the size of the clusters were quite 

 different then from those entertained at present, and Mr. Barnard had hoped that precise 

 measures with the large telescope would reveal internal motions within a few years. He 

 extended his triangulations to many other globular clusters until he had finally included in his 

 program 20 clusters. In spite of his ardor and his experience as a photographer, Mr. Barnard 

 stdl found it difficult to recognize the superior advantages of the measurement of star clusters 

 on photographs with the use of rectangular coordinates. He put his trust in the filar microm- 

 eter more than in the measuring machine, particularly because he could recognize certain of 

 the cluster stars as triple, which were confused in a single image on the photograph then at hand, 

 taken with an instrument of one-fifth the focal length of the great refractor. A very few years 

 later, when remarkably fine photographs had been secured by G. W. Ritchey with the 40-inch 

 telescope, through a yellow filter and with the double-slide plate holder, Mr. Barnard measured 

 some photographs of the clusters, and in subsequent years took some equally good ones himself. 

 The excellent accordance between his measures on the negatives and those he made visually 

 with the micrometer was to him an evidence that astrometric investigations could be satis- 

 factorily made by photography; to his colleagues this accordance was a demonstration of Bar- 

 nard's extraordinary skill at the telescope with the micrometer. Similarly, when his visual 

 determination of the parallax of Krueger 60 was very closely confirmed by Schlesinger's meas- 

 ures on plates taken with the 40-inch telescope, it convinced Barnard that good parallaxes could 

 be obtained by the new photographic method; while for us it was again a demonstration of 

 Barnard's great skill as an observer. 



It was probably no small disappointment to Mr. Barnard that his measures in the clusters, 

 continued for nearly 25 years, yielded so little in the way of proper motions — in fact, it could 

 hardly be asserted that a single one of the cluster stars showed an appreciable motion with 

 respect to its fellows. From what we know now, it would have been better to omit much of this 

 labor by visual methods, and to trust to photographic records made from time to time for the 

 establishment of the motions which certainly must exist, but which will evidently require a long 

 lapse of time for accurate determination. Progress is being made in the considerable task of 

 evaluating these micrometric measures which were expressed in position angles and distances, 

 and referred to selected stars in the clusters. In Messier 5, 239 stars were included; in Messier 

 13, 247; and in several other clusters the numbers run over 100. The measures certainly repre- 

 sent accurately the positions of the selected stars during the score of years that they were under 

 Barnard's observation. Plans were begun some 15 years ago for the publication of these meas- 

 ures; but they were delayed in the natural hope that with a longer time some evidences of 

 motion would be established. Considerable attention was given during this work to following 

 changes in brightness of some of the variables, and a few new variables were discovered by 

 Professor Barnard in the clusters. He observed, in particular, Badey's No. 33 in Messier 5, 

 and determined its period with great precision, contributing half a dozen papers to the discus- 

 sion of this star alone during the score of years that he observed it. At first he thought that the 

 period was constant, but later the continued observations showed that it first lengthened, then 

 shortened. 



Although Mr. Barnard would naturally not be regarded as a regular observer of variable 

 stars, he nevertheless discovered some 10 of these objects, most of them visually, and he 

 followed particular ones for many years; thus, he published three papers on the period and 

 variation of RS Aquarii, which he discovered visually in 1898. He also followed rather closely 

 several especially interesting stars of this sort, discovered by others, which required large 

 optical power when they were near minimum. 



The novae were of especial interest to him. He determined their positions micrometrically 

 with great precision with respect to neighboring stars; he estimated carefully their fluctuations 

 in light, and noted the change in focus which resulted from their change in spectrum when the 

 stars were too faint to be observed spectroscopically; he examined them minutely with the 

 great telescope to detect the presence about them of nebulous shells or phenomena of that 



