■i5° 



NA TURE 



[December 18, 1902 



LETTERS TO THE EDITOR. 



[ The Editor does not hold himself responsible for opinions ex- 

 pressed 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 communications. ,] 



Secular Changes of Climate. 

 For some time past it has been generally believed that the 

 climate of Central Asia was once less arid than at present, but 

 we now know, as Dr. Sven Hedin explained to the Royal Geo- 

 graphical Society on December 8 (p. 134), that important 

 changes have taken place since the Christian era began. He 

 found in the Lob Nor region forests with the trees long dead, 

 traces of a road, ruined villages, coins, manuscripts and other 

 relics which proved the northern shore of the old salt lake (now 

 dry) to have been cultivated and occupied, down to about 

 sixteen centuries ago, by a fairly civilised people. This, I 

 think, implies a rainfall, less inappreciable than the present one, 

 during the earlier centuries of that era, and the change, as he 

 found dead forests, cannot be attributed (as in parts of southern 

 Europe and Syria) to reckless destruction by the hand of man. 

 But, besides this, Sir Norman and Dr. W. J. S. Lockyer have 

 recently proved (in a communication to the Royal Society) a 

 very remarkable correspondence to exist between the distribu- 

 tion of the periodic rains in India, Mauritius and elsewhere and 

 the amount of solar activity, and they have, within the last few 

 days, drawn the attention of the same Society to the fact that 

 zones of abnormally high and low mean barometric pressure 

 exist on opposite sides of the earth and oscillate from the one 

 position to the other in accordance with the periodic small 

 variations of solar activity. Dr. Sven Hedin's discovery ap- 

 parently indicates a change secular rather than periodic, but 

 may not both operate independently, as in the case of changes 

 due to variations of eccentricity in the earth's orbit and to pre- 

 cession of the axis of rotation ? The authors of those papers 

 admit the existence of disturbing causes, some of which may be 

 local, but not necessarily all. Is it, then, possible that these 

 discoveries may afford a clue to the solution of two great geo- 

 logical puzzles — the abnormal temperatures of the Pleistocene 

 and of early Tertiary times ? In regard to the former, many 

 now believe that the climate of North Central Europe when the 

 loess was deposited more nearly resembled that of the Caspian 

 steppes, and all maintain that in the Glacial epoch the 

 mean temperature of the whole continent was much below 

 what it is now. How much this was, at the time of 

 greatest cold, is not easily estimated, but a few years 

 ago I attempted a rough approximation. This will be 

 found in a volume of the Contemporary Science Series 

 called "Ice Work" (part iii. chap, i.), and the results (for 

 Europe) are as follows : — Supposing the British Isles to be at 

 their present level (in order to avoid the controversy as to the 

 origin of Boulder-clays and Glacial gravels), the mean tempera- 

 ture of these islands at the present Ordnance Datum would 

 have to be lowered by about 20° F. The same would probably 

 hold good of Scandinavia — at any rate, that would suffice to 

 make either country much more closely resemble a corresponding 

 part of Greenland. In the more central parts of Europe, the 

 problem is rather easier, for here we are undoubtedly dealing 

 with " land-ice." A fall of 18° in the mean temperature would 

 suffice for the Alps; perhaps rather less, 15 or 16°, for the 

 Pyrenees, the Sierras Guadarrama and Nevada, possibly also 

 for the breccia-producing age on the Rock of Gibraltar. A re- 

 duction of 18 at most, and more probably about 16 or 15 , 

 would bring back small glaciers to Auvergne, the Schwarzwald, 

 Vosges, Apennines, Corsican mountains, the Caucasus and even 

 the Atlas. I may add that a reduction of 15° appears sufficient 

 to form a great ice-sheet in North America, and that in the 

 southern hemisphere and at Mount Kenya in Africa distinctly 

 smaller change suffices. All these estimates assume the present 

 levels maintained ; they may be corrected at the rate of 1 for 

 each 300 feet of elevation or depression. But geologists too 

 often forget that the anomaly of early Tertiary heat is not less 

 difficult to explain than that of Pleistocene cold, for in later 

 Eocene ages the mean temperature of southern England can 

 hardly have been less than 20 above that which it now enjoys. 

 The explanations which have been offered for the Glacial epoch 

 — a different arrangement of sea and land, variations in eccen- 

 tricity, precessional movements (none of which, in my opinion, 

 are more than partially successful) — cannot be applied to the 



NO. I 729, VOL. 6/] 



latter case, so that we seem compelled to seek for some other 

 cause. Variations in solar heat have been already suggested, 

 but hitherto this hypothesis has seemed too much a Deus ex 

 mackind. But as Dr. Sven Hedin's discoveries show that im- 

 portant alterations in climate have been in progress during the 

 last fifteen or sixteen centuries, and Sir Norman Lockyer's re- 

 searches indicate that comparatively small changes in solar 

 activity produce rather important meteorological effects upon 

 the earth, geologists qualified for the investigation may find it 

 not unprofitable to follow up the clue. T. G. BONNEY. 



The Government Grant for Scientific Research. 



Now that the annual advertisement of the Government 

 grant is once more appearing, I should like to call attention 

 to the long interval that elapses between the date appointed 

 for the reception of applications for, and that of making known 

 the distribution of, the grants. The former is fixed for January 

 31, the latter is some time in May, a period of more than three 

 months. This seems to me to detract somewhat from the 

 value of the grants, for, in certain instances at least, the con- 

 ditions may have quite altered in so long a time and the 

 possibility of making a particular research have passed away. 



King's College, December 8. R. T. Hewlett. 



The Unconscious Mind. 



In a recent review ( November 20) of my book on the " Force 

 of Mind," " VV. McD." remarks, "The book is vitiated 

 throughout by the insistence upon the part supposed to be 

 played by the unconscious mind." 



But a closer attention to the argument would have revealed 

 the fact that, while no stickler for a word and still less an 

 advocate for two minds, the author is compelled to give some 

 name for mental processes unaccompanied by consciousness. 



The position of the man who denies any mental processes at 

 all, as distinguished from mechanical, is logical ; but the position 

 of the man who distinguishes mental processes (that is, processes 

 which a machine cannot conduct apart from mind) from mechan- 

 ical, and at the same time will only recognise as mental those 

 accompanied by consciousness, is illogical. The self-same 

 mental process at one time may be conducted in consciousness 

 and at another outside it, and he is therefore on the horns of 

 this painful dilemma. He must either at one time call the 

 process mental and at the other mechanical or " nervous," or he 

 must extend the word "consciousness" so as to include the 

 unconscious. To a psychologist, the consequences of such a 

 theory are deplorable and are described in scathing terms by 

 Prof. James 1 when he depicts the present state of this conserv- 

 ative science ; while with a medical man it compels him logically 

 to regard cases of neuromimesis as malingering or fraud because 

 he sees the disease has mental characteristics, and yet cannot, 

 according to the old psychological shibboleth, recognise as mind 

 the unconscious psychic agent. I may say in conclusion that the 

 need lor this extension of mind has been felt by none more keenly 

 than by the very psychologists who have refused it. The 

 student o( this subject has only to turn to Prof. C. T. Ladd's 

 " Philosophy of Mind," p. 395, and compare it with p. 393 ; or 

 to Prof. Sully's " Illusions," pp. 266 and 335, to see the existence 

 of unconscious mental actions both asserted and denied in the 

 same book. 



These passages and others will all be found in my work '- on 

 the subject. A. T. Schofield. 



6 Harley Street, W. , December 1 5. 



Dr. Schofield objects to my strictures on his extensive 

 application of " the unconscious " as an explanatory principle 

 that solves (for him) all problems of the relations of body and 

 spirit. And he persists in confusing the question of the validity 

 of " the unconscious " with the question of the propriety of so 

 extending the use of the terms " mind "and "mental" as to make 

 them applicable to brain activities that do not involve affections 

 of consciousness. This extended use of the words I myself, 

 following Dr. Bastian, have urged and adopted, but to do this 

 is not to commit oneself to the hypothesis of " the unconscious 

 mind." Dr. Schofield's use of this phrase implies the assump- 

 tion of a factor in mental life that is neither neural process nor 

 conscious process, but an utterly unknown, unknowable and 

 mysterious third agent, more or less intervening between the two 



1 Prof. W. James, " Psychology," p. 468. 



-Dr. Schofield, "The Unconscious Mind," 2nd edition. (Hodder and 

 Stoughton.) 



