2 68 



THE POPULAR SCIENCE MONTHLY. 



on page 111 : "His Western explorations 

 were begun in 1870, when he visited the 

 cretaceous region of Western Kansas." Is 

 not this date a mistake ? Professor Marsh, 

 of Yale College, in November, 1870, fitted 

 out an expedition at Fort Wallace, and ex- 

 plored the cretaceous deposits of Western 

 Kansas during November and December of 

 that year. In June, 1871, he again started 

 with an expedition from the same fort, and 

 spent about two months in exploring the 

 same region. 



I am quite sure that Professor Cope did 

 not visit Western Kansas until after Pro- 

 fessor Marsh's second season's work was 

 completed. 



There are some other similar errors in 

 this sketch which should perhaps be noticed, 

 but the one mentioned I can correct of my 



own knowledge. 



M. D. 



Manhattan, Kansas, October 25, 18S1. 



INFLUENCE OF TEMPERATURE ON THE 

 CHIRP OF THE CRICKET. 



Messrs. Editors. 



Some years ago my attention was called 

 to the crickets which chirp so incessantly 

 every summer evening, and it was thought 

 by a friend that they varied in the number 

 of their chirps per minute at a 



higher 



temperature vibrating much faster. At that 

 time a single observation was made, but for 

 some reason was not repeated. 



Recently, a writer in the " Salem Ga- 

 zette," signing himself W. G. B., gives the fol- 

 lowing rule for estimating the temperature of 

 the air by the number of chirps made by the 

 crickets per minute : " Take seventy-two as 

 the number of strokes per minute at 60 

 temperature, and for every four strokes 

 more add 1, and for every four strokes 

 less deduct the same." After seeing this 

 I determined to make a number of observa- 



tions, to find out if this were an invariable 

 rule. I tried it, with one or two exceptions, 

 every night that the crickets chirped, from 

 September 30th to October 17th. During 

 this period a heavy frost occurred, when 

 the crickets were not heard, but as soon as 

 the weather grew warmer they began again. 

 The lowest temperature at which they were 

 heard was 50. By the observations given, 

 it will be seen that the temperature as es- 

 timated from the number of the crickets' 

 chirps varies a degree or more from that re- 

 corded by the thermometer, but it must be 

 remembered that no standard thermometer 

 was used, and that the crickets were chirp- 

 ing in the trees, in many cases sheltered 

 from the wind, while the thermometer hung 

 near a window in a more exposed position ; 

 also, that on cool evenings it was very diffi- 

 cult to count the strokes, as they were fee- 



ble and interrupted. Below are 

 observations for twelve evenings : 



the 



It will be seen, by the above, that there 

 is a remarkable accordance between the 

 number of vibrations and the temperature 

 of the air. With more accurate observa- 

 tions doubtless a closer agreement would be 

 proved. Margarette W. Brooks. 



Salem, Massachusetts, October 22, 1881. 



EDITOR'S TABLE. 



FURTHER LESSONS OF THE YOBKTOWN 

 CENTENNIAL. 



THE recent centennial proceedings 

 at Yorktown, and the event they 

 commemorated, have been so fully dis- 

 cussed in all quarters and in all as- 

 Bpects, that the topic is now pretty 

 well exhausted. We certainly can not 

 add anything to it in the way of nov- 

 elty, but among the lessons that have 

 been drawn from it there are some 

 which deserve greater emphasis than 



they seem to have received. The ora- 

 tors of this occasion have expatiated 

 much on the Yorktown surrender as a 

 great step in the progress of human 

 liberty : it is worth while to inquire to 

 what extent and in what sense this is 

 true. 



The capture of Cornwallis ended a 

 protracted war, and by the success of 

 the insurgents turned the infamy of a re- 

 bellion into the glory of a revolution. 

 It secured political independence, and 



