Nov. 4, 1880] 



NATURE 



fauna as elsewhere, each species varying within its definite 

 range as each species appears to have varied at all times 

 past and present" (p. 50). 



Exactly so ; the abyssal species are like species else- 

 where. The difficulties in the way of the application of 

 the evolution of species by variation and selection there- 

 fore in this case cannot be greater than elewhere. In 

 fact, from the sentences which end the " Introduction " it 

 seems doubtful whether they are not less than in many 

 other cases. 



"Transition forms linking species so closely as to cause 

 a doubt as to their limit are rarely met with. There is 

 usually no difficulty in telling what a thing is " (p. 50). 



Hence it appears that the study of the abyssal fauna 

 has satisfied Sir Wyville Thomson that transitional 

 forms are sometimes met with ; and that, sometimes, he 

 has found a difficulty in " telling what a thing is." And 

 this admission is all that the most ardent disciple of Mr. 

 Darwin could desire. 



However, the value of the great work whicli is now 

 being brought before the public does not lie in the specu- 

 lations which may be based upon it, but in the mass and 

 the solidity of the permanent additions which it makes to 

 our knowledge of natural fact. Sir Wyville Thomson 

 and his colleagues must be congratulated on having made 

 an excellent beginning ; the looker-on may properly content 

 himself with wishing them a speedy and a good ending. 



T. H. Huxley 



THE LAVA-FIELDS OF NORTH-WESTERN 

 EUROPE 



FROM the earliest times of human tradition the basin 

 of the Mediterranean has been the region from which 

 our ideas of volcanoes and volcanic action have been 

 derived. When the old classical mythology passed away 

 and men began to form a more intelligent conception of 

 a nether region of fire, it was from the burning moun- 

 tains of that basin that the facts were derived which 

 infant philosophy sought to explain. Pindar sang of the 

 crimson floods of fire that rolled down from the summit 

 of Etna to the sea as the buried Typhoeus struggled 

 under his mountain load. Strabo, with matter-of-fact 

 precision and praiseworthy accuracy, described the erup- 

 tions of Sicily and the Aeolian Islands, and pointed out 

 that Vesuvius, though it had never been known as an 

 active volcano, yet bore unequivocal marks of having 

 once been corroded by fires that had eventually died out 

 from want of fuel. In later centuries, as the circle of 

 human knowledge and experience has widened, it has 

 still been by the Mediterranean type that the volcanic 

 phenomena of other countries have been judged. When a 

 geologist thinks or writes of volcanoes and volcanic action, 

 it is the structure and products of such mountains as Etna 

 and Vesuvius that are present to his mind. Nowhere 

 over the whole surface of the globe have eruptions been 

 ■witnessed different in kind though varying in degree from 

 those of the Mediterranean vents. And hence even among 

 those who have specially devoted themselves to the study 

 of volcanoes there has been a tacit assumption that from 

 the earliest times and in all countries of the world where 

 volcanic outbreaks have occurred, it has been from local 

 vents like those of Etna, the Aeolian Islands, the Phleg- 

 raean Fields, or the Greek Archipelago. 



If one were to assert that this assumption is probably 

 erroneous, that the type of volcanic " cones and craters " 

 has not been in every geological age and all over the 

 earth's surface the prevalent one, that, on the contrary, it 

 is the less portentous, though possibly always the most 

 frequent type of volcanic action, and belongs perhaps to 

 a feebler or waning degree of volcanic excitement — these 

 statements would be received by most European geologists 

 with incredulity, if not with some more pronounced form 

 of dissent. Yet I am convinced that they are well 

 founded, and that a striking illustration of their truth is 

 supplied by the greatest of all the episodes in the volcanic 

 history of Europe — that of the basalt-plateaux of the 

 north-west. 



It is now some twelve years since Richthofen pointed 

 out that on the Pacific slope of North America there is 

 evidence of the emission of vast floods of lava without 

 the formation of cones and craters. Geologists interested 

 in these matters may remember with what destructive 

 energy Scrope reviewed his " Natural System of Volcanic 

 Rocks"; how he likened it to the old crude ideas that 

 had been in vogue in his younger days, and which a 

 study of the classical district of Auvergne had done so 

 much to dispel ; and how he ridiculed what he regarded 

 as "fanciful ideas" and "untenable distinctions," which 

 it was " a miserable thing ' ' to find still taught in mining- 

 schools abroad. My own reverence for the teaching of 

 so eminent a master and so warm-hearted a friend led me 

 to acquiesce without question in the dictum of the author 

 of " Considerations on Volcanoes." Having rambled over 

 Auvergne with his admirable sections and descriptions 

 in my hand, 1 knew his contention as to the removal of 

 cones and craters by denudation and the survival of more 

 or less fragmentary plateaux once connected with true 

 cones to be undoubtedly correct with respect at least to 

 that region. Nevertheless there were features of former 

 volcanic action on which the phenomena of modern volca- 

 noes seemed to me to throw very little light. In particu- 

 lar the vast number of fissures which in Britain had been 

 filled with basalt and now formed the well-known and 

 abundant " dykes " appeared hardly to connect them- 

 selves with any known phase of volcanism. The area 

 over which these dykes can be traced is probably not less 

 than 100,000 square miles, for they occur from Yorkshire 

 to Orkney, and from Donegal to the mouth of the Tay. 

 As they pierce formations of every age, including the 

 Chalk, as they traverse even the largest faults and cross 

 from one group of rocks into another without interrup- 

 tion or deflection, as they become more numerous towards 

 the great basaltic plateaux of Antrim and the Inner 

 Hebrides, and as they penetrate the older portions of 

 these plateaux, I inferred that the dykes probably be- 

 longed to the great volcanic period which witnessed the 

 outburst of these western basalts. Further research has 

 fully confirmed this inference. There can be no doubt that 

 the outpouring of these great floods of lava of which the 

 hills of Antrim, Mull, Morven, Skye, Faroe, and part of 

 Iceland are merely surviving fragments and the extrava- 

 sation of these thousands of dykes are connected mani- 

 festations of volcanic energy during the Miocene period. 



But this association of thin nearly level sheets of basalt 

 piled over each other to a depth of sometimes 3,000 feet, 

 with lava-filled fissures sometimes 200 miles distant from 



