554 The Smithsonian Institution 



fessor Orme Masson; and that for 1891 contains an interesting 

 paper by Professor Hallock, on the "Flow of Solids," orig- 

 inally published as a bulletin by the United States Geological 

 Survey. Under the same general class is the memoir by 

 Professor Edward W. Morley on " The Densities of Oxygen 

 and Hydrogen and the Ratio of their Atomic Weights," which 

 appeared as one of the " Smithsonian Contributions" in 1895. 

 In this elaborate research Professor Morley was assisted by 

 grants from the Smithsonian Institution, and he was thus en- 

 abled to make by far the most exhaustive study of the subject 

 that has yet appeared, and his results are everywhere acknow- 

 ledged to possess a degree of accuracy hitherto unapproached. 

 Reference must not be omitted to a few papers of no great 

 length, but of extreme interest and value, more fully related 

 to dynamical problems, and especially to the theory and 

 measurement of the force of gravitation. Among them is 

 one on the " Nature and Origin of Force," by Doctor William 

 B. Taylor, printed in the Smithsonian Report for 1870, and 

 another by the same author, on " Kinetic Theories of Gravi- 

 tation," published in 1876. The last is a particularly valuable 

 critical history of the most important theories regarding 

 gravitation from Newton to Clerk Maxwell. In the Report 

 for 1888 there is a somewhat condensed account of Wilsing's 

 determination of the density of the earth by his ingenious 

 "pendulum balance" method. It is worth while remarking, 

 in reference to this, that the Smithsonian Institution has for 

 many years rendered cooperative assistance to scientific men 

 engaged in the determination of the value of the force of 

 gravity. A special room in the basement of the building, 

 particularly adapted to this work, was long ago set aside for 

 use as a pendulum room, and it was for many years regarded 

 as the "base station" for the extensive gravity work of the 

 United States Coast and Geodetic Survey. 



