12 REPORT OF THE SECRETARY. 



surface of tlie moon is of special and growing interest to geologists, 

 wlio have rarely access to the largest class of telescopes, and what we 

 know of it is derived very largely from maps made from eye-studies by 

 astronomers. 



Within a few years photography has beeu used with such increasing 

 advantage in this interesting field, that it is believed by those compe- 

 tent to express an opinion, that i^hotographs can shortly be produced 

 which will exliibit in a i)ermanent form everything that a trained eye 

 can recognize at the most i^owerful telescope. If this surprising result 

 be not actually obtained, I am of opinion that it is attainable; and I 

 have proposed to procure, through the association of the Smithsonian 

 Institution with some of tlie leading observatories of the world, a series 

 of photographic representations of hitherto unequaled size and defini- 

 tion, which shall represent the moon's snrfiice as ftir as possible on a 

 definite scale, and entirely without the intervention of the draftsman. 

 Photographs of the moon made at the Harvard, Lick, and Paris observ- 

 atories have been placed at the disposition of the Smithsonian Institu- 

 tion for publication, and it is intended to issue a series of them accom- 

 panied by explanatory text. Whether this considerable work shall 

 appear as one of the regular series of "Contributions to Knowledge,"' 

 or as a special publication in a more limited edition, has not yet been 

 decided. 



Smithsonian Tables. — The meteorological and i)hysical tables, originally 

 prepared by Dr. Guyot and first published in 1851, have been in such 

 demand that they have already passed through four editions. The last 

 edition was exhausted several years ago, and in considering the advisa- 

 bility of issuing a fifth edition, it was determined in 1887 to rev^ise the 

 tables to conform to the present state of our knowledge. The work has 

 been divided into three parts, meteorological, geographical, and i)hysi- 

 cal, each one being independent of the others, but the three capable of 

 forming a homogeneous volume. 



In carrying out this plan I was able to secure the assistance of Prof. 

 William Libbey, jr., of Princeton, under w hose editorship the last edi- 

 tion was issued in 1884, and Prof. Libbey, devoting gratuitously such 

 time to the work as he could command from his engrossing college duties, 

 prepared the first volume of the series, the "Meteorological Tables." 

 The plan of the work was then somewhat modified and a farther re- 

 vision was made by Mr. G. E. Curtis, who was at the time emj^loyed upon 

 other work at the Smithsonian Institution, and by the end of December, 

 1891, the manuscript was essentially ready i'ov the printer. Since that 

 timeit has been passing through thejiress, and it is hoped thait the volume 

 will be entirely finished by the close of the present calendar year. 



SMITHSONIAN INTERNATIONAL EXCHANGE SERVICE. 



The international exchange service, through which the Smithsonian 

 Institution is known to most of the large libraries and to a vast num- 



