170 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 3 5 



part in many phases of human activity. To it we owe the first sub- 

 division of the year into months and weeks, even though in our 

 present calendar the lunar cycle is disregarded. The words moon 

 and month are derived from the same Sanskrit root, mas, meaning to 

 measure. To our primitive ancestors the moon was an object of 

 worship; they observed and tried to explain its changes in aspect 

 and in position among the stars from day to day. Together with the 

 sun it is responsible for the tides, so important to navigation. Its 

 light illuminates the sky at night during a part of each month and 

 its moonbeams are said to be an important factor in certain human 

 decisions. To the formulation of the law of gravitation and to the 

 development of dynamical astronomy it contributed much, but to 

 modern astrophysics it has added little and it cannot compete with 

 other heavenly bodies as an object of study. The astronomer of to- 

 day does not appreciate the moon as did Milton when he wrote in 

 Paradise Lost: 



* * * The moon 

 Rising in clouded majesty, at lengtli 

 Apparent queen, unveiled her peerless light 

 And over the dark her silver mantle threw. 



In 1609 Galileo first observed through his telescope the surface 

 features of the moon, its craters, mountains, and great plains or seas, 

 as he called them. liealizing that the moon is a companion of the 

 earth and, as he thought, a world not unlike our own, he was 

 impressed by the features which he saw, and sought to interpret 

 them in terms of terrestrial features. To him and to his contempo- 

 raries his telescope seemed to disclose a new world. Following his 

 lead, astronomers undertook serious study of the moon's surface. 

 During the next 3 centuries a vast amount of observational data on 

 lunar surface features was accumulated and many lunar maps were 

 published. As a result, the geography or rather selenography of the 

 moon is well known ; no part of the moon's surface visible to us has 

 been left unexplored. Furthei-more, selenologists have sought to 

 explain the mode of formation of the different features on the moon's 

 surface and have suggested all manner of hypotheses to account for 

 them. In spite of all this labor we do not yet know definitely the 

 exact nature of the lunar surface materials, nor how any single 

 lunar feature was formed. No critical study and classification of 

 lunar surface features have been made and no lunar maps free from 

 the personal factor have been prepared. 



COOPERATIVE APPROACH 



At the time the committee on study of the surface features of 

 the moon was appointed. Dr. John C Merriam felt that attack by 

 a cooperative Carnegie Institution group might be fruitful of 



