Page:Popular Science Monthly Volume 27.djvu/419

Rh by electricity) the beats of its standard clock over the telegraph 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 observe 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 assume 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 Pittsburg 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 Professor 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 conscious of undue brevity. One has a sense, in reading, that every