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SCIENCE. 



[Vol. XX. No. 512 



as with the white ant and mud-wasp are the results of intelligent 

 observation and experience. 



But it has become automatic ! Brain and manipulating organs 

 fulfil their allotted task without experience and instruction ! 



Here the parallelism with man is certainly no longer perfect; 

 there is a divergence, but a divergence due only to the same laws 

 acting on two sets of modified conditions. Man has developed by 

 ■radiation in ever-widening circles and is still in course of an all- 

 iround development. The insect has developed along a narrow 

 Jine and has reached the limit of his capacity, but that limit sur- 

 passes man's utmort attainments, both in clearness of perception 

 without intellectual effort, and in facility of execution. The 

 knowledge and capacity of execution gained by observation and 

 'experience have become constitutional. Man, in spite of the 

 great breadth of his intellectual range, does occasionally reach 

 •something like the inherited clearness of perception and facility 

 tot execution of the insect, at special points of the circle ; as, for 

 ■example, in the inherited musical powers of a Mozart and other 

 born composers, who have been capable of composing as auto- 

 ■matically as the bee makes its cell ; and I assume for both a 

 ■similar intellectual gratification in the exercise of their powers, 

 liook again at the born arithmeticians and mathematicians; or, 

 again, at the achievements of a Siemens. Does any one suppose 

 that these involve the intellectual labor performed by the average 

 ■tyro struggling to overcome some petty difficulty? Great results 

 -have unquestionably been achieved by enforced attention and 

 ■patient labor, but the greatest achievements arise by unconscious 

 ■reflex action of the brain to the stimulus of inherited memories 

 which evolves the idea before it even rises into consciousness. It 

 as precisely this clearness of perception and facility of execution, 

 lecognized as genius in man, which characterize the special labors 

 ■of insects and other of the lower animals in their special narrow 

 fields. Further, all naturalists who have given close study to the 

 hymenoptera, for instance, will, I think, support me in the con- 

 ■clusion that the automatic facility displayed in their special tasks 

 "lis accompanied with intellectual resources which enable them to 

 •deal intelligently with emergencies which may arise in the course 

 «of their performance. 



We may And a still closer parallelism between man and the 

 "lower animals in the matter both of inherited perceptions and 

 ■capacities of performance on a lower intellectual plane, which 

 being part of every man's experience, the relation of inherited to 

 :acquired ability will be the more readily appreciated. Every 

 •child knows intuitively that an apple is good to eat. On this 

 point his perceptions are clear, his convictions not to be shaken. 

 This is a familiar instance of inherited perception or brain 

 imemory. In fighting we have an illustration of muscle-memory. 

 A fistic encounter calls forth as diversified and complicated a 

 ■series of activities as almost any species of manual labor, but a 

 ten-year-old boy of fighting stock will stand up to his first fight 

 and play his part with a skill and address and promptitude such 

 as he could not acquire in any industrial pursuit without consid- 

 ■erable training. 



These are only particular illustrations of a well-known general 

 •law. Any muscular or mental labor long persisted in is attended 

 •with a facility of execution which in time becomes constitutional 

 ;in the race. Man is immeasurably removed from the lower ani- 

 mals by his wider range of perceptions and capacities, but we 

 -cannot form a better idea of the intellectual status of the lower 

 animals, within their narrow limits, than by speculating on a fu- 

 ■ture ideal stage of human evolution, when every child bom into 

 'the world will, as his intellect unfolds, display, without instruc- 

 tion, the mathematical genius of a Euclid, the musical powers of 

 sa Mozart, the logical powers of a Bacon, and the comprehension 

 of character of a Shakespeare. 



THE DATE OF THE LAST GLACIAL EPOCH. 



BY MAJOK-GENBEAL I. C. COWELL, WINDSOR, ENGLAND. 



Now that the untiring labors and vast research of such men as 

 IProfessors Wright, Prestwich, and Emerson, Dr. Andrews, and 

 Slessrs. Gilbert and D. Mackintosh have resulted in such remarka- 



ble coincidences as to the period of the termination of the last glacial 

 epoch, England, as America, may well be congratulated upon 

 such achievements by their men of science in that intensely inter- 

 esting field of enquiry ; but our satisfaction would be far from 

 complete if we did not find confirmation of these results in those 

 of astronomical discovery, which give evidence of that perfect 

 harmony which has so long been sought for in vain by astronomers 

 and geologists and by all those who have awaited the revelation 

 which unquestioned facts have at last disclosed. These are to be 

 found in the beautiful discovery of Major General Drayson of the 

 Royal Artillery (formerly professor of astronomy at the Royal 

 Military Academy at Woolwich) of the second rotation of the 

 earth, whose works, entitled "30,000 Years of the Earth's Past 

 History" and '-Untrodden Ground in Astronomy and Geology" 

 (published by Chapman & Hall and by Paul, Triibner & Co. of 

 London), afford the most striking testimony to the accuracy of the 

 calculations of the gentlemen referred to. 



In so short a notice as this it is only possible to give a general 

 outline of the discovery, which has occupied nearly thirty years 

 for its full development, resulting in the discovery that the glacial 

 period, or, more properly speaking, periods, occupy about 20,000 

 years, whilst the last terminated about 6,000 years ago. This, 

 however, is but one of the results of the discovery. 



The earth has three principal movements, the first being its 

 daily rotation, the second the annual revolution of the earth round 

 the sun, and the third a slow second rotation of the earth which 

 causes the half axes of daily rotation to trace cones during a period 

 of about 31,600 years. 



The second rotation, more accurately defined, consists in the 

 pole of the heavens describing a circle round a point, which is 

 ascertained to be situated six degrees distant from the pole of the 

 ecliptic, having a right ascension of 370 degrees, and at an angu- 

 lar distance from the pole of the heavens of 39° 25' 47", this angle 

 depending upon the position of the centre of gravity of the earth, 

 the earth being considered as a gyrating sphere, and so following 

 the ordinary laws of gyration. 



The two semi- axes of the earth by this movement describe cones, 

 having their apices at the centre of gravity, which in the case of 

 the earth nearly corresponds to the centre of the sphere. From 

 the knowledge of this law, and from these data, the polar distance 

 of a star can be at once calculated for more than a hundred years 

 from one observation only, and to the decimal of a second of an 

 arc, a result which hitherto could only be attained by constant 

 observation and laborious calculations by the method adopted by 

 astronomers in ignorance of the properties of this rotation. 



The obliquity of the ecliptic can be ascertained for any time 

 during the revolution of the poles, which are calculated to occupy 

 81.683 years in completing the circle. Hitherto the time supposed 

 for the completion of this conical motion was about 25,000 years, 

 during which period scarcely any variation occurred — so it was 

 asserted — in the extent of the Arctic circles and tropics. 



By a knowledge of the second rotation it is proved that a varia- 

 tion of twelve degrees in the extent of the Arctic Circle and 

 tropics occurred not later than 18,500 B.C. The procession of the 

 equinoxes is ascertained to be the result of this second rotation, 

 and due to no other cause ; and the rate of procession can be ascer- 

 tained at any time, this, it may be mentioned, being proportionate 

 to the sine of the obliquity of the ecliptic at the time indicated, 

 in its every- varying amount from the minimum of 23° 25 ' 47" to 

 the maximum of 35° 25' 47''. 



With such a difference, it follows that at the height of the 

 glacial period — that is, when the obliquity attains to 35° 25' 

 47" — the Arctic Circle will have crept down towards the equator 

 in both hemispheres twelve degrees, which will thus cause the 

 tropics to extend to the same amount towards the poles, and so 

 extend the tropical zone from Cape Hatteras to the River Plate. 



Under such conditions the human mind fails to conceive the 

 vast changes which must be brought about during every six 

 months from the mighty floods caused by the intense summer 

 heat and the intense cold of the Arctic winter, alternating with 

 each other. 



It is to such changes of temperature that we find the remains 

 of Arctic and tropical animals imbedded together in the same 



