ADVERTISEMENT. 



A QUARTER of a ceiituiy has now elapsed since the publication of the 

 last (the third) edition of Dr. Guyot's Meteorological and Physical Tables. 

 This forms the first of an early projected series of "Tables of Constants" 

 to which the Smithsonian Institution is gradually making important 

 contributions. None has been in more general demand than this collec- 

 tion, and to its improvement and extension Prof. Guyot gratuitously 

 devoted a large amount of time and laborious attention. 



The first edition, published in 1852, comprised 212 pages. Five years 

 later (in 1857) a second edition was published, with careful revision by 

 the author; and the various series of Tables were so enlarged as to ex- 

 tend the work to over 600 pages. A third edition was published in 

 1859, with further amendments. 



To this, the author, with untiring industry, has been making constant 

 additions; and the present issue projected by him in 1879 — from various 

 delays occasioned by pressing professional occupations, as well as by 

 illness and death in his family — has been about four years in passing 

 through the press. The result is at last submitted in this fourth edition, 

 which extends to about 750 pages. 



Just before completing the last few tables, the estimable and dis- 

 tinguished author departed this life, February 8, 1884, in the seventy- 

 seventh year of his age. Dr. Guyot had for thirty yeai's been the honored 

 Professor of Geology and Physical Geograjliy in Princeton College. 



The completion of the work has been entruste<l to his able assistant, 

 Prof. William Libbey, Jr., who has conscientiously and judiciously exe- 

 cuted his duties as the final editor. In the Preface to this edition he 

 has indicated the character of the additions and re-arrangements adopted. 



SPEITCER F. BAIRD, 



Secretary S. I. 



Washington, September, 1884. 



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