September 30, 1901.] 



SCIENCE. 



423 



less perfect in their theories. Primarily, 

 also, it should be observed, geophysics is 

 not simply a part of, but is the very 

 foundation of, astronomy; for the earth 

 furnishes the orientation, the base-line, and 

 the timepiece by means of which the as- 

 tronomer explores the heavens. Geology, 

 likewise, in the broader sense of the term, 

 as Ave are now coming to see, is a funda- 

 mental science not only by reason of its 

 interpretations of terrestrial phenomena, 

 but also by reason of its parallel interpreta- 

 tions of celestial phenomena; for there is 

 little doubt that in the evolution of the 

 earth we may read a history which is in 

 large degree typical of the history of 

 celestial bodies. In any revised estimate, 

 therefore, of the relative rank of the phys- 

 ical sciences, while it would be impossible 

 to lower the science of the heavens, it would 

 appear essential to raise the sciences of the 

 earth to a miich higher plane of importance 

 than was thought appropriate by our pre- 

 decessors of a hundred yeare ago. 



As with physics, chemistry and astron- 

 omy, the wonderful progress of the nine- 

 teenth century in geophysical science has 

 been along lines converging towards the 

 more recondite properties of matter. All 

 parts of the earth, through observation, 

 experiment, induction and deduction, have 

 yielded increasing evidence of limited 

 unities amid endless diversities. Adopting 

 the convenient terminology of geologists 

 for the different shells of the earth, let us 

 glance rapidly in turn at the sciences of 

 the atmosphere, the hydrosphere or oceans, 

 the lithosphere or crust, and the eentro- 

 sphere or nucleus. 



The atmosphere is the special province 

 of meteorologists, and although they are 

 not yet able to issue long-range predictions, 

 like those guaranteed by our theories of 

 tides and terrestrial magnetism, it must be 

 admitted that they have made great prog- 

 ress towards a rational description of the 



apparently erratic phenomena of the 

 weather. One of. the peculiar anomalies 

 of this science illustrates in a striking way 

 the general need of additional knowledge 

 of the properties of matter; in this case, 

 especially, the properties of gases. It is 

 the fact that in meteorology greater prog- 

 ress has been made, up to date, in the inter- 

 pretation of the kinetic than in the inter- 

 pretation of the static phenomena of the 

 atmosphere. Considering that static prop- 

 erties are usually much simpler than 

 kinetic properties, it seems strange that 

 we should know much more about cy- 

 clones, for example, than we do about 

 the mass and the mass distribution of the 

 atmosphere. In respect to this apparently 

 simple question meteorology seems to have 

 made no advance beyond the work of La- 

 place. There are indications, however, 

 that this, along with many other questions, 

 must await the advent of ' a new Principia. ' 



The geodesists, who are the closest allies 

 of the astronomers, may be said to preside 

 over the hydrosphere, since most of their 

 theories as well as most of their observa- 

 tions are referred to the sea level. They 

 have determined the shape and the size of 

 the earth to a surprising degTee of cer- 

 tainty; but they are now confronted by 

 problems which depend chiefly on the mass 

 and mass distribution of the earth. The 

 exquisite refinement of their observational 

 methods has brought to light a minute 

 wandering in the earth of its axis of rota- 

 tion, which makes the latitude of any place 

 a variable quantity ; but the interpretation 

 of this phenomenon is again a physical 

 and not a mensurational problem. They 

 have worked improvements also in all kinds 

 of apparatus for refined measurements, as 

 of base-lines, angles and differences of 

 level; but here, likewise, they appear to 

 approach limits set by the properties of 

 matter. 



The lithosphere was once thought to be 



