80 KEY. A. IRVING, B.A., B.SC, ON EVOLUTIONARY LAW 



within the liorizon of our mental vision : although here, as 

 with vital evolution, we may he thrown back upon the 

 hypothesis of a dirccfinfj injliicace which eludes our powers of 

 analysis.* 



I A shallow criticism coukl, a few years ago, ridicule the notion 

 (of light appearing in this glohe before the sun and the stars 

 fare taken into account ; 1)uL that criticism, like much other 

 criticism of the same fibre, is now seen to have been a little 

 " too previous." The earth was passing through the " solar 

 phase " of its existence, and was a sun to itself. 



As condensation proceeded about the original barysphere, the 

 luminous gaseous matter of our planet, with that of the other 

 planets and of the central orl) of the system, became more and 

 more separated, with an intervening dark expanse of space; the 

 liuid matter (" the waters of the earth was marked oft* from 

 that of the other members of our system by terrestrial, 

 planetary, and solar gravitation. Kendered poetically, " God 

 mid, Let there he an ejepanse in the niidd of the VKUers."1[ 



Loss of heat by radiation into space allowed the gradual 

 liquefaction of the mineral matter of the globe, with a gradual 

 formation of a thin " crust " in the " pre-oceanic stage," the two 

 together making u]j the "lithosphere " of the globe ; and with 

 further fall of temperature of the whole mass by radiation of 

 heat, the watery and other vapours l)egan to condense upon the 

 still hot crust, giving rise to such widespread vulcanicity as 

 that of which we can read the evidence in the moon's surface ; 

 the globe became in time covered with a mantle of hot water, 

 above which, as a physical necessity, there must have floated a 

 dense " atmosphere," impervious except even to the most 

 diffused light from the sun, even if that central orb had, at that 



(period of the history of our solar system, entered upon its 

 sola?^ phase of condensation (see Loi'd Kelvin's address to the 

 Victoria Institute, 1897). 



At the stage in the history of our planet following upon the 

 formation of its " hydrosphere," we may fairly place tlu^ 

 Cambrian and Silurian fauna of the universal ocean, the 

 t(Mnpei ature of which was not less than 80° F., over the whole 



* Mr. Jeans' plirase ^ravitatioiinl instability" is a useful one in this 

 connection. (See A'nlu/y, Oct. Ii^tli, 1!)()5, ]). 591.) The heaviest and 

 most ref)-actory metals, such as i>latinum, would be tlie tirst ])rol)ably to 

 form the luicleus of the bai}sphere, but a gravitational centre once 

 formed, gravitation would be rapidly augmented. 



t For an al)le discussion of the term " tlie waters," see Hugh Capron's 

 7'//^' Covfiict of Truth, (cliap. xiii.) 



