Page:Popular Science Monthly Volume 20.djvu/280

268 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 explored 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 Professor 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.

October 25, 1881.

Messrs. Editors.

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 Gazette," signing himself W. G. B., gives the following 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 observations, 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 estimated from the number of the crickets' chirps varies a degree or more from that recorded by the thermometer, but it must be remembered that no standard thermometer was used, and that the crickets were chirping 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 difficult to count the strokes, as they were feeble and interrupted. Below are observations for twelve evenings:

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 observations doubtless a closer agreement would be proved.

October 22, 1881.



HE recent centennial proceedings at Yorktown, and the event they commemorated, have been so fully discussed in all quarters and in all aspects, that the topic is now pretty well exhausted. We certainly can not add anything to it in the way of novelty, but among the lessons that have been drawn from it there are some which deserve greater emphasis than they seem to have received. The orators 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 rebellion into the glory of a revolution. It secured political independence, and 