I 4 MODERN SCIENCE: 



brief step brief indeed compared with the real problems of Astronomy, 

 for which latter it is probably quite inadequate. 



Tycho Brahe, excellent astronomer as he was, kept as we saw tcTthe 

 epicycle theory. He imagined that the moon's path round the earth was 

 a fixed combination of cycle and epicycle. Kepler introduced the con- 

 ception of the ellipse. Later on the motion of the perigee and other 

 deviations compelled the abandonment of the ellipse and the supposition 

 of an endless curve, similar to an ellipse at any one point, and main- 

 taining a fixed mean distance from the earth, but never returning on itself 

 or making a definite closed figure of any kind. Finally the researches of 

 Mr. George Darwin have destroyed the conception of the fixed mean 

 distance, and introduced that of a continually enlarging spiral. Cer- 

 tainly no four theories could well be more distinct from each other than 

 these ; yet if an eclipse had to be calculated for next year it would 

 scarcely matter which theory was used. The truth is that the actual 

 problem is so vast that a prediction of a few years in advance only touches 

 the fringe of it so to speak ; yet if the fulfilment of the prediction were 

 taken as a proof of the theory in each of these different cases, it would 

 lead us in the end to the most hopelessly contradictory results. 



The success of a prediction therefore only shows that the theory on 

 which it is founded has had practical value so far as a working hypothesis. 

 As working hypotheses, as long as they are kept down to brief steps which 

 can be verified, the scientific theories are very valuable indeed we could 

 not do without them ; but when they are treated as objective facts 

 when, for instance, the "law of gravitation " derived as it is from a brief 

 study of the heavenly bodies has a universal truth ascribed to it, and is 

 made to apply to phenomena extending over millions of years, and to 

 warrant unverifiable prophecies about the planetary orbits, or statements 

 about the age of the earth and the duration of the solar system all one 

 can say is that those who argue so are flying off at a tangent from actual 

 facts. For as the tangent represents the direction of a curve over a small 

 arc, so these theories represent the bearing of facts well enough over a 

 small region of observation ; but as following the tangent we soon lose 

 the curve, so following these theories for any distance beyond the region 

 of actual observation we speedily part company with facts. l 



To proceed with a few more words about the general method of 

 Science. Science passes from phenomena to laws, from individual details 



i All our thoughts, theories, "laws," &c., may perhaps be said to touch Nature as 

 the tangent touches the curve at a point. They give a direction and are true at that 

 point. But make the slightest move, and they all have to be reconstructed. The tan- 

 gents are infinite in number, but the curve is one. This may not only illustrate the 

 relation of Nature to Science, but also of Art to the materials it uses. The poet radiates 

 thoughts; but he sets no store by them. He knows his thoughts are not true in them- 

 selves, but they touch the Truth. His lines are the envelope of the curve which is his 

 poem. 



