NE 17, 1922] 



NATURE 



775 



Letters to the Editor. 



The Editor dees riot hold himself responsible for 

 opinions expressed by his correspondents. Neither 

 can he undertake to return^ or to correspond with 

 the writers of rejected manuscripts intended for 

 this or any other part of Nature. No notice is 

 taken of anonymous commumcations.'\ 



Geology and the Nebular Theory. 



The literature of geology has grown so immense 

 that no man can be familiar with all of it, particularly 

 jwhen it refers to another continent than one's own, 

 jt it comes as a surprise to a Canadian to find 

 linent Old World geologists still referring to the 

 jbular hypothesis as an established fact of geological 

 story. A few weeks ago Prof. J. W. Gregory 

 iggested that life began on mountains, since these 

 ;re the first parts of the earth's crust to cool to a 

 itable temperature, and more recently Prof. Joly, 

 discussing the age of the earth, assumes the truth 

 the nebular hypothesis, though he admits that 

 there was indeed some scanty sedimentation in 

 rchaean times." 



Probably no country includes a larger area of 

 rchaean rocks than Canada, and several parts of the 

 2a have been studied as carefully as possible because 

 their importance as mining regions, yet no evidence 

 of a hot earth has been found. The Huronian rocks 

 of cobalt include a glacial deposit which is known to 

 have covered many thousands of square miles. The 

 Sudbury or Timiskaming Series, next in age, consists 

 almost entirely of sediments, such as boulder con- 

 glomerates which may be glacial, arkosi with un- 

 weathered feldspars, and graywacke with seasonal 

 leanding. Near Sudbury the series has a thickness 

 of more than 20,000 feet. 



The oldest rocks of all are the Keewatin and the 

 Grenville Series, the former consisting mainly of 

 \olcanics but including thousands of feet of sedi- 

 mentary gneisses and of " iron formation " ; the latter 

 is made up wholly of sediments, reaching a thickness 

 of more than 50,000 feet in places and containing 

 immense deposits of limestone, as well as much 

 carbon in the form of graphite. 



It might be thought that the Keewatin lavas imply 

 a hot condition of the earth, but as a fact most of 

 tliem exhibit pillow structure, showing that they were 

 poured out into water. Liquid water existed over 

 many thousands of square miles, and probably the 

 temperature was low enough for the life of algae and 

 perhaps of primitive animals, as suggested by the 

 carbon and limestone. The rocks of this most 

 ancient known geological period do not indicate a 

 higher temperature than that of later times. 



It is probable, however, that those geologists who 

 think of the earth as hot in Archaean times have in 

 mind the granites and gneisses which underhe the 

 most ancient sediments, the Laurentian rocks of 

 Canada and similar plutonic rocks of other countries, 

 which undoubtedly are of eruptive origin, and have 

 been described as part of the original crust of the 

 molten earth. In reality the Laurentian batholiths 

 are far younger than the sediments and volcanics of 

 the Keewatin and Grenville which they have invaded, 

 and a similar welling-up of plutonic batholiths has 

 occurred at numerous times in the later history of 

 the world, and is perhaps still taking place beneath 

 great ranges of youthful mountains like the Andes 

 and Himalayas. 



The coast range of British Columbia, iioo mUes 

 long and 100 broad, consists of just as characteristic 

 batholithic rocks as the Laurentian, but is of Jurassic 



NO. 2746, VOL. 109] 



age, and the Andes, which are still younger, appear 

 to be largely of the same character. Granite and 

 gneiss may be of any age, and do not imply a cooling 

 earth as some have supposed. We find greater areas 

 of such plutonic rocks in the most ancient geological 

 periods simply because they have been exposed to 

 denudation for a longer time, and so have been more 

 widely uncovered. 



The conditions found in the Archaean of Canada 

 are repeated in Brazil, India, and Scotland, and prob- 

 ably other countries of which the present writer has 

 no personal knowledge. The oldest rocks in the 

 world are sedimentary and indicate temperatures like 

 those of later times. If the earth was ever a molten 

 sphere, there is no evidence of this condition in the 

 geological record, and geologists should not cling to 

 an outworn theory which the astronomers themselves 

 have largely given up. In the planetesimal theory a 

 method of world building has been provided which 

 permits of a cold surface from the beginning, and fits 

 far better with the known geological facts than the 

 nebular theory. A. P. Coleman. 



University of Toronto, Toronto, Canada, May 16. 



Species and Adaptations. 



Mr. Bateson's address to the American Association 

 at Toronto last December, which was published in 

 Nature of April 29, exhibits features of the same 

 kind as those which were evident in his address to 

 the British Association in Australia in 1914. In the 

 Australian address he maintained that the efifect of 

 the discoveries and investigations in recent years in 

 the phenomena of heredity and variation was greatly 

 to increase the difficulty of understanding the origin 

 of any characters which were new in the proper sense 

 of the word. He went so far as to suggest that all 

 characters which have appeared in the course of 

 evolution may have been present in the protoplasm 

 or nuclear structure of the original unicellular forms 

 from which later forms, including man, have descended, 

 all apparently new characters having been due to loss 

 of inhibiting factors and segregation of various 

 simpler combinations from the original complex. 

 Now Mr. Bateson again declares himself an agnostic 

 with" regard to the evolution of species, and in spite 

 of aU modern discoveries, or because of them, states 

 that we are farther than ever from any satisfactory 

 explanation of the evolution of a new species, or of 

 two or more species, from a single ancestral species. 



Mr. Bateson admits that plenty of Mendelian 

 combinations would in nature be given specific rank, 

 and then proceeds to state that the topic of evolution 

 is now dropped in genetical circles. He then illus- 

 trates the rule of silence on this favourite subject of 

 a former generation by devoting the rest of his dis- 

 course to it, only to lead up to the conclusion that 

 specific difference probably " attaches " to a base of 

 which we know absolutely nothing at all. Our faith 

 in evolution, Mr. Bateson declares, is unshaken ; our 

 doubts are merely as to the origin of species. 



Now I have no intention of stating in opposition to 

 Mr. Bateson that our present knowledge fully explains 

 the origin of new species ; I wish merely to offer 

 some criticisms of the difficulties which he describes. 

 In the first place, I dishke the expression "faith in 

 evolution." I do not share the distrust in facts and 

 reasoning which is now in vogue as a reaction against 

 the excessive confidence of the nineteenth century. 

 Evolution is a question of science, of verifiable facts 

 and sound reasoning, and has nothing to do with 

 faith. Mr. Bateson himself in another paragraph 



