SKETCH OF PROFESSOR S. P. LANGLEY. 403 



raatically by electricity) the beats of its standard clock over the tele- 

 graph lines from New York and Philadelphia west as far as Cincinnati 

 and Chicago, north to Lake Erie, and south to Washington. This 

 system is still in full operation, and has always maintained a high 

 character for accuracy. 



The United States Coast Survey organized several parties to ob- 

 serve the total eclipses of 1869 and 1870, and Professor Langley went 

 to Oakland, Kentucky, in 1869, as a member of the party of his friend 

 Professor Winlock, Director of Harvard College Observatory. In 

 1869 his station was upon the very edge of the shadow, and the 

 object of his observation was to determine the limit of total eclipse. 

 In 1870 the station assigned to Professor Langley was at Xeres, in 

 Spain, where he determined the polarization of the solar corona to 

 be radial. 



During the year 1870 the affairs of the observatory began to as- 

 sume such a shape that some time for original work in astronomy was 

 available. The success of the time-service had created a small fund 

 out of which the more pressing needs of instrumental equipment were 

 provided ; and Professor Langley now began a period of the most 

 incessant work on the minute study of the features of the sun's disk. 

 The situation of his observatory at Pittsburg, where dense clouds of 

 smoke and dust and dirt obscure the heavens, and the meager state 

 of his instrumental equipment, almost forced him to take up the 

 study of the sun, which has light enough to penetrate even a Pitts- 

 burg fog. Fortunately, this study demanded very few auxiliary pieces 

 of apparatus : the telescope has to be directed upon the sun, its motor- 

 clock keeps it constantly pointed upon the same spot, and the observer 

 has to follow, with infinite diligence and patience, the elusive details 

 which the moments of best vision may allow him to glimpse. Two 

 very important and rare qualifications are also necessary. The observer 

 must be entirely unprejudiced and impartial ; recording that which 

 he sees, whether it is expected or not, and recording nothing which he 

 does not see, no matter how firmly he may be convinced that it ought 

 to be visible. This is the first qualification one of unusual mental 

 constitution ; and the second is one of unusual manual skill. The 

 observer must be able to delineate the most extraordinary and complex 

 details justly and correctly. Both of these unusual qualifications Pro- 

 fessor Langley possesses in a marked degree. His well-known and 

 most beautiful drawing of a " Typical Sun-spot " illustrates this. This 

 has since been copied in very many places, and it has received the 

 very highest praises from all competent judges. 



Professor Langley's earliest published paper on the sun (February, 

 1874) may be taken as a type of his best work. It possesses that 

 hardly-definable quality by which we become aware that it was written 

 from a full mind. It is only fifteen pages long, yet we are not con- 

 scious of undue brevity. One has a sense, in reading, that every state- 



