NO. 8 SAMUEL PIERPONT LANGLEY ABBOT 3 



conversation. He was fond, for instance, of the expressions : " Let 

 sleeping dogs lie " ; " The written word remains " ; " What has pos- 

 terity done for us that we should care so much for the opinion of 

 posterity? " One day when he was going to some function he came 

 hurriedly out of his room and said " William, my hat." The colored 

 man ran and got his derby. " I said a HAT! " shouted Langley, as 

 he threw the derby down the hall. He used always to have a messenger 

 boy accompany him when he walked to outlying offices. As befitted 

 his chief's dignity, the boy always walked two paces behind, perhaps 

 carrying an overcoat or a portfolio. In his youthful exuberance, and 

 especially if some crony was looking on, the boy might cut some 

 slightly disrespectful capers. But if so, he reckoned without his 

 chief's knowledge of optics. For observing the boy indistinctly by 

 reflection from the rear of his glasses, Langley would turn around 

 suddenly at a critical moment, to the boy's great discomfiture. These 

 little idiosyncrasies were a spice to us at the time, and endear the 

 memory of our great chief as we look back over more than a quarter 

 century. 



In the remainder of this memoir I propose to let Langley tell in his 

 own words of some of his leading pioneer investigations. A list of 

 the exact references to these articles will be found at the end of this 

 paper. 



" ON THE MINUTE STRUCTURE OF THE SOLAR PHOTOSPHERE " 



" Before we turn with these aids to the study of the photosphere, 

 it will be well to describe briefly appearances presented by the solar 

 surface in telescopes of moderate size. 



** Here we see a disk of nearly uniform brightness, which is yet 

 sensibly darker near the circumference than at the center. Usually 

 seen relieved against this gray and near the edges, are elongated and 

 irregular white patches (factilae), and at certain epochs trains of spots 

 are scattered across the disk in two principal zones equidistant from 

 the solar equator. On attentive examination it is further seen that 

 the surface of the sun everywhere — even near the center and where 

 commonly neither faculae nor spots are visible — is not absolutely 

 uniform, but is made up of fleecy clouds, whose outlines are all but 

 indistinguishable. The appearance of snow flakes which have fallen 

 sparsely upon a white cloth, partly renders the impression, but no 

 strictly adequate comparison can perhaps be found, as under more 

 painstaking scrutiny, we discern numerous faint dots on the white 

 ground, which seem to aid in producing the impression of a moss- 



