CORRESP ONDENCE. 



841 



CORRESPONDENCE. 



CLOSE OF THE GLACIAL PERIOD. 

 Editor Popular Science Monthly ; 



GKOLOGISTS who are only slightly versed 

 in astronomy are apt to make a serious mis- 

 take on this subject. The latest which has 

 fallen under my notice is by Prestwich. in 

 the article entitled The Position of Geology, 

 in the February number of this periodical, page 

 541. He says: "The last of these astro- 

 nomical periods was calculated to have com- 

 menced two hundred and fifty thousand years 

 and to have ended eighty thousand years ago. 

 These numbers have become stereotyped as 

 those of the beginning and the end of the 

 Glacial period." 



A slight acquaintance with this subject 

 ought to prevent mistakes such as the above. 

 They are stereotyped only to those who give 

 little or no heed to the actual dates and as 

 little to a universal law of Nature touching 

 the cumulative effects of constantly acting 

 forces. These effects were clearly set forth 

 by Prof. Le Conte some years ago in treat- 

 ing of this general subject. The day of the 

 summer solstice is not the day of greatest 

 heat or the middle of the hot season ; nor is 

 the day of the winter solstice in the middle 

 of the cold season. The maximum in the 

 two cases occurs about six weeks after those 

 dates respectively, an amount about equal 

 to one fourth of the whole time from one ex- 

 treme to the other. These are elementary 

 truths, and whoever omits them in this dis- 

 cussion repeats the old story of "playing 

 Hamlet with Hamlet left out." 



The following is a brief statement of the 

 essential points in the case: Two hundred 

 and fifty thousand years ago * the eccentrici- 

 ty of the earth's orbit was very nearly what 

 it is now, and consequently the climate of 

 these two distant periods, so far as it may 

 depend on the eccentricity, was not very 

 different. The eccentricity had been less, 

 but was then increasing, and had so been for 

 ten thousand years. It continued to increase 

 for about fifty thousand years longer, becom- 

 ing then nearly three times its present value. 

 Then for another like period it diminished 

 till it became about once and a half its pres- 

 ent value. Then again for a second time it 

 increased for about fifty thousand years, be- 

 coming about two and a half times the origi- 

 nal value. This was one hundred thousand 

 years ago. The decline again commenced, 

 and eighty thousand years ago the eccentricity 

 was more than double its present value. It is 

 therefore evident is plain as an axiom 

 that the Glacial period did not end then and 



* J3ee American Journal of Science, August, 1880. 



there. The eccentricity continued to be 

 greater than it is now for twenty thousand 

 years more. And for this long period of one 

 hundred and ninety thousand years the eccen- 

 tricity, on the average, was more than twice 

 what it is now. Those who disregard these 

 facts have not fully grasped the question. 

 It would better accord with truth to say that 

 sixty thousand years ago the Glacial period 

 was making ready " to go out of business." 



If we allow only thirty thousand years for 

 the undoing of the effects of the one hundred 

 and ninety thousand and the allowance is 

 certainly moderate the close of the Glacial 

 period was only thirty thousand years ago, 

 and that date is comparatively recent when 

 counting geological time. It appears, then, 

 that there is no irreconcilable difference be- 

 tween those geologists who reject Croll's 

 theory by reason of the alleged remoteness 

 of the Glacial period and those who think 

 there " may be something " in that theory. 

 And the more especially is this the case 

 since the recent discovery of the old outlet 

 of the upper lakes through Lake Nipissing 

 and the Ottawa River and the relatively late 

 period when the waters of all the upper lakes 

 began to flow to the sea by way of the 

 Niagara. R. W. McFARLAND. 



COLUMBUS, OHIO, February, 1894. 



DOG PSYCHOLOGY. 



Editor Papular Science Monthly ; 



DEAR SIR : I was greatly interested hi Mr. 

 Monteith's article on " The Psychology of the 

 Dog," in the February number, and desire to 

 supplement his paper with some observations 

 of a dog of my own. The animal was a pug 

 not full-blooded, but with a cross of some 

 other kind ; yet he had all the characteristic 

 markings of that breed, and his general ap- 

 pearance was the same, except that his nose 

 was a trifle longer and not so stubby. 



"Gyp" was intelligent to a remarkable 

 degree, and from some of his actions I firmly 

 believe that he not only understood what was 

 said to him, but he was capable also of con- 

 tinuous thought, and could reach conclusions. 

 That he understood many words, and could 

 distinguish between them, I am satisfied. 



His mistress taught him that when some 

 candy was placed before him, of which he 

 was very fond, if she said, "That's Demo- 

 crat," he must not touch it, but when the 

 word " Republican " was uttered he at once 

 ate it. 



When "Gyp" was thirsty he would go 

 into the kitchen and sit patiently at the sink 

 waiting for a drink ; but if, after waiting for 



