May 24, 1895.] 



SCIENCE. 



563 



earth did not cliaiigo to any /orf/c extent; 

 that most of the apparent changes in hiti- 

 tude were due to errors of observation and 

 defects in theory, but he thouglit it probable 

 that muiU changes did occur in the position 

 of the pole : he thought the changes were 

 periodic, and did not amount to more than 

 two minutes of arc equal to about 12.0(IU 

 feet. '' Thus, instead of several degrees 

 which were conceded by the astronomers of 

 of previous centuries, but a paltry two min- 

 utes was now allowed ; but with improved 

 instruments, •with the discovery of aberra- 

 tion and nutation and the perfection of the 

 theorj- of refraction, even this modest al- 

 lowance was gradually reduced to a vanish- 

 ing quantity.' 



The geologists, in their investigations, 

 have found fossil remains in the cold regions 

 of the north, belonging to the Miocene. 

 Upper and lower Cretaceous, Jurassic and 

 other geological periods, which seem to in- 

 dicate a former temperature much higher 

 than the present. In 1870 Dr. John 

 Evans, then President of the British Geo- 

 logical Societj-, discussed the problem, and 

 concluded that the amount of polar light 

 and heat in the past must have been much 

 greater than it is now. He invited the at- 

 tention of the mathematicians to this prob- 

 lem, and asked : Would a considerable ele- 

 vation and depression of the sea bottoms and 

 continents produce a ' change of 1.5 degrees 

 to 20 degrees in the position of the pole ? ' 



Sir "William Thomson discussed this 

 problem and gave his conclusions in 1870 

 to the British Association for Advancement 

 of Science. He said: " Consider the great 

 facts of the Himalayas and Andes and 

 Africa, and the deptiis of the Atlantic, and 

 America and the depths of the Pacific, and 

 Australia; and consider further the ellip- 

 ticity of the equatorial section of the sea 

 level, estimated by Colonel Clarke at about 

 one-tenth of the mean ellipticity of tiie 

 meridianal sections of the sea level. 



" "We need no brush from a comet's tail to 

 account for a change in the earth's axis ; 

 we need no violent convulsions producing 

 a sudden distortion on a great scale, with 

 change of axis of maximum moment of 

 inertia, followed by gigantic deluges; and 

 we may not merely admit, but assert as 

 highly probable, that the axis of maximum 

 inertia and the axis of rotation, always 

 near one another, may have been in ancient 

 times very far from their present geograi)h- 

 ical position, and maj- have gradually- shifted 

 through ten, twenty, thirty or forty or more 

 degrees without at any time any perceptible 

 sudden disturbance of either land or water." 



Sir William Thomson gave no account of 

 the calculations made by him as the basis 

 of these conclusions. 



In 1877 Mr. G. H. Darwin made a care- 

 ful and elaborate mathematical discussion 

 of the problem. He showed that, in a per- 

 fectly rigid globe, the pole could not have 

 wandered more than 3 degrees from its 

 original position, as the result of the con- 

 tinents and oceans changing places. "If, 

 however, the earth is sufficientlj' plastic to 

 admit of readjustment to new forms of 

 equilibrium, by earthquakes and otherwise, 

 l)ossible changes of ten or fifteen degrees 

 may have occurred. This would require, 

 however, such a complete changing about 

 of the continents and oceans, with maximum 

 elevations and depressions in precisely the 

 most favorable places, as has certainly never 

 occurred in geologic times." 



The evidence indicates, in fact, that the 

 continental areas have alwaj's occupied 

 about the same positions as now. 



Thus it would seem that the geologists . 

 must abandon the hypothesis of great 

 changes in latitude as a factor in the earth's 

 development, unless a new cause can be 

 found that will move the pole to the extent 

 rccjuired by the geologists. 



In an addre.'^s made l)efore Section A, of 

 tlie British Association in 18i»2, Profe-ssor 



