December 22. 1892] 



NATURE 



171 



was not entirely assertion. They were very fond of facts, 

 and undoubtedly preferred founding their dogmatism 

 upon them — indeed, nothing could be more distasteful 

 than to suppose each- dogma had not a sound basis. 

 In most cases the worst of which they can even now be 

 accused is that the facts were often above their compre- 

 hension, or were understood in the wrong sense. . But 

 these men would have scorned the grounding of their 

 dogmas upon imagination. They were perfectly aware 

 (only it had not then been so neatly put) that " Imagina- 

 tion is the fire of Discovery : the best of servants though 

 the worst of masters." Now the Assertive school, of which 

 in this country Mr. Dixon, if he was not the joint-invent- 

 or, may be looked upon as a chief leader, rests nearly all 

 on imagination. It matters little whether there is reason 

 behind their assertions or not, and generally, we regret to 

 say, there is none. Conjectures follow upon conjectures 

 and are put forward for the most part as if they were 

 serious deductions from observation. It is not so many 

 weeks since some words, that seem very applicable here 

 were addressed to a scientific audience : — 



" We have had enough of the untrained writer of 

 papers, the jerry-builder of unfounded hypotheses whose 

 ruins cumber our field of work." ' 



Mr. Dixon, with his long string of previous books, may 

 demur to being termed a writer of this kind ; but he 

 certainly needs to be taught the meaning of the word 

 " probable " and its derivatives. When he has learned it 

 perhaps he will use it in its fit sense. With him, at 

 present, it is in many cases to be rendered " possible," 

 while in not a few impossible would be the true equiv- 

 alent. Now according to all etymologists, and the harm- 

 less drudges known as dictionary-makers, "probable" 

 signifies something that can be proved. Any reader of 

 average intellect will be able to calculate how seldom this 

 unhappy word is correctly used by Mr. Dixon. It has 

 long been a custom in certain fevers to affix an ice-cap 

 on the patient's head whereby the burning brow is cooled, 

 ;ind some temporary relief afforded ; but of late years, as 

 pretty well all know, there has sprung up a small group 

 of writers to whom ice on the brain, instead of being a 

 soothing remedy, is a direct incentive to acts and diets 

 bordering upon lunacy. On behalf of the Glacial Epoch, 

 1 he Post-Pliocene Glacial Epoch, to be very particular, 

 we must protest against its being constantly paraded as 

 I he greatest event in the history of the globe, to which 

 in its momentous effects all others must give place. That 

 it produced considerable changes and especially in the 

 ;,^eographical distribution of plants and animals none can 

 doubt, but that it is accountable for all that Mr. Dixon 

 ^ays to its charge is hardly likely, and is most decidedly 

 not " probable," since means of proof are wanting. But 

 Mr. Dixon, with others of the Assertive school, is not con- 

 sistent in his statements, and is apt to forget on one page 

 what he has written on a preceding one. For instance, 

 we are told (p. 33) that " From the commencement of this 

 Glacial Epoch, the Migration of birds, as we see it at the 

 present time, was probably initialed " ; and yet, only a few 

 ines further on, our author declares " that we do not re- 

 quire even the occurrence of one Glacial Epoch to account 

 for the Migration of birds," and (p. 34) that " such a cause 



' British Association for the Advancement of Science. Edinburgh, 1892. 

 Address of the President of Section H (Nature, vol. xlvi. p. 379). 



NO. 1208, VOL. 47] 



amply sufficient in every respect is to be found in the 

 varying places of Earth's \sic'\ orbital eccentricity in com- 

 bination with the precession of the equinoxes" — this 

 statement being immediately followed by a passage, the 

 application, or even the meaning, of which is not easy to 

 understand : — 



" That these majestic phenomena are in any conceiv- 

 able way connected with the migratory movements of 

 birds seems utterly impossible ; but in them the habit 

 has its root ; and the simple season-flight of a Cuckoo or 

 a Nightingale to and fro between the shores of Africa and 

 England is inseparably and directly connected with the 

 erratic movement of a planet in its orbit ; nay, with the 

 constitution of a universe ! " 



This note of admiration is our author's own : far be it 

 from us to impair its influence. 



Though we have confined our remarks to the earlier 

 part of Mr, Dixon's book, we have already devoted a good 

 deal of space to him. There is, however, another point 

 on which we must say a few words. He has tjirown out 

 a direct challenge to Nature, and we should be sorry 

 not to meet it. That he believes in migration the whole 

 volume shows ; but there is yet left in his mind a cranny 

 wherein lurks what we may perhaps call a " pious 

 opinion" in favour of torpidity — as a luxury in which 

 a lazy bird may occasionally indulge, even though that 

 bird may be one possessing powers of flight far beyond 

 the average. He is very severe on an anonymous 

 reviewer in these columns in that the " Theory," we use 

 Mr. Dixon's word, of Torpidity " was subjected by him 

 to the bitterest ridicule and denounced as folly." There- 

 upon he favours us (pp. 12, 13) with another version 

 (substantially, let us say at once, the same as the 

 original, but with fewer details) of the story told by the 

 Duke of Argyll in these pages (Nature, vol. xv. pp. 527, 

 528) to say nothing of some other observations, quite 

 irrelevant, as it seems to us, communicated by his Grace 

 to him. But further than this, he cites as an additional 

 witness in defence of the impeached " Theory," Dr. 

 Elliott Coues, who is said to give it " all the support of his 

 authority as an ornithologist of the highest eminence." 

 Now we have a great respect for that gentleman, but his 

 vast reputation fails to hypnotize us, and such support 

 as he gave has already been the subject of comment in 

 these pages (Nature, vol. xx. p. 2). He will hardly be 

 comforted to learnj that the supposition there made has 

 been amply confirmed of late by Mr. Hartert, who informs 

 us {Cat. B. Brit. Mus. vol. xvi. p. 481) that the British 

 Museum contains five specimens of Chceturapelagica from 

 Central America, beside the one before noticedfrom Mexico 

 — proving that its range is much about what might have 

 been expected. Thus all the argument based on Dr. 

 Coues's statement, that this species was " not known to 

 winter anywhere out of the United States, nor is it found 

 anywhere in them at that season," falls to the ground, as 

 we are sure that gentleman will readily admit. We 

 allow that it has been very naughty of naturalists if they 

 did prepare this pitfall for Mr. Dixon ; but that is not 

 our business, and we cannot imagine they did it inten- 

 tionally. It is not unlikely that the Chimney-Swift flew 

 out of shot, or too fast for them to bring it down, but 

 they have at last succeeded in "grassing" their bird, 

 with a result so disastrous to the " Theory." One chance 



