1870] WRITINGS OF JOSEPH HENRY. 461 



S-UGGESTIONS AS TO THE ESTABLISHMENT OP A PHYSICAL 

 OBSERVATORY.* 



(From the Smithsonian Annual Report for 1870, pp. 141-144.) 



Decembe?' 29, 1870. 



My Dear Sir: Yours of the 2Sth of November was duly 

 received, but I delayed answering it until the pressure of 

 business which accumulated during my absence should have 

 somewhat subsided, and also that I might receive the plans 

 which you mention. I am now gratified in being able to 

 inform you that my visit to Europe was both pleasant and 

 profitable, and that T have returned much inproved in health, 

 and with enlarged views as to the present state of science in 

 the Old AVorld. 



While abroad I gave special attention to physical obser- 

 vatories, of which there are several in England and on the 

 continent, although no one of them fully realizes my idea 

 of what such an establishment ought to be. 



A physical observatory is one the primary object of which 

 is to investigate the physical phenomena of the earth and the 

 heavenly bodies in contradistinction to an ordinary astronom- 

 ical observatory, which is principally devoted to the observa- 

 tion anddiscussionof the motions of the planets, and the deter- 

 mination of the relative positions of the fixed stars. Of the 

 latter kind but one or two are needed in any country, and as 

 these require a numerous corps of observers and computers 

 they can only be supported by appropriations annually from 

 a national government. The United States Observator}'- at 

 Washington is of this character, and including all expenses 

 requires an annual appropriation of at least $50,000. The 

 labors of such an observatory are indispensibleto the advance- 

 ment of the science of theoretical astronomy, and its appli- 

 cation to geodesy and geography. 



The establishment I would advise you to found is of the 

 character of the one first mentioned, namely a physical ob- 

 servatory, the principal object of which would be, as I have 



*[A letter addressed to Mr. Leander McCormick, dated Washington, 

 December 29, 1870.] 



