4 SCIENCE PROGRESS. 



strengthening, the country requires opening up, railways 

 and telegraphs require to be organised. 



Of the three great branches of science — cosmology, 

 chemistry, and biology — the first has benefited most by 

 physical science. One of its most advanced branches, 

 astronomy, is almost a dependency on physical science. 

 Since Sir Isaac Newton's time the motions of the stars, 

 the motion of the earth, the tides, have been almost entirely 

 reduced to be branches of pure dynamics. Still there are 

 outlying branches even here. The motions of meteors, 

 the constitution of the sun, the tides themselves have not 

 been fully explained by known physical causes. In the 

 other branches of cosmology, geology, and geography, the 

 connections with physical science are great, but do not 

 at all equal in extent the connections with astronomy. 

 Many, many outlying branches are still unsupplied with 

 connections. To enumerate even a few of the directions 

 in which these connecting links may be strengthened, it 

 may be worth while suggesting investigation of the velo- 

 cities of meteors by photography. All that is required is 

 a periodic eclipsing of the plate at known short intervals 

 of time. Any meteoric path photographed would then 

 be interrupted at regular known intervals, and a simple 

 calculation founded on the observed length of path photo- 

 graphed between the interruptions, would tell us with 

 considerable accuracy the angular velocity of the meteor ; 

 a velocity only known now in the very vaguest way. 

 The study of the deformation of the crust of the earth 

 by solar and lunar gravitation is a connecting link be- 

 tween physics and cosmology, that requires considerable 

 strengthening. We are told on one hand, on the highest 

 authority, that the earth is solid to the core ; and, on the 

 other hand, that the investigations upon which this result 

 is based have been gone over very carefully, and do not 

 lead to that conclusion at all. Is the earth rig-id ? How 

 do mountains stand ? What are the causes of the earth 

 breathings, of the motion of the pole, of earthquakes ? Can 

 glaciers erode the bottoms of rock hollows ? Do we see 

 in the periodic variations of terrestrial magnetism any 



