2G6 HENRY C. MCCOOK. 



between the growth of the hills as compared with each other, and in 

 the growth of the same hill at different periods. It seemed possible 

 however to make a rough estimate of the rate of progress. Adjoin- 

 ing the wood in which the ant city is located is a field owned by a 

 Mr. Prough, a farmer long resident in the neighborhood. Several 

 hills had sprung up in this field, since the last crop had been taken 

 from it. This seemed to promise the data for calculation. The field 

 had been plowed in September, 1875. The following measurements 

 were made by Mr. Prcugh and Mr. John McGinnis, February, 1877, 

 viz. : Hill No. 1, 8 ft. 9 in. around the base, 10 in. high, 2 ft. 11 in. 

 in diameter. Hill No. 2, 11 ft. 4 in. around the base, 14 in. high, 

 4 ft. in diameter. Also, in a corn field plowed July, 1876, two hills 

 were measured, each of which had the following dimensions: Nos. 3, 

 41 ft. around the base, 8 in. high, 1 ft. 6 in. in diameter. Nos. 1 and 

 2 are the result of but a little more than one year's work, viz. : from 

 September, 1875, to November, 1870, at or before which time the frost 

 stops all work, Nos. 3 exhibit the result of about two months active 

 labor, one-third of the working season. The amount of work done 

 may be thus calculated (roundly); in No. 1, 1] cu. ft. per year; No. 

 2, 3 cu. ft. per year; Nos. 3, each 1 cu. ft. per year. 



Hill No. 2 exhibits the most remarkable increase, having attained 

 more than half the average size of the matui-e hills (if I may use 

 that expression), in little more than a year. It may be that this was 

 simply the re-erection of a hill that had beeil ploughed over, and of 

 course went on more rapidly as a large community at once centered 

 all efforts upon the work. Nos. 3 seem to be examples of growth on 

 the part of new communities. Making allowance for the varying 

 progress occasioned by varying communal exigencies, we may estimate 

 the time required to complete a mature hill to be from five to seven 

 years. After that the activity of the workers finds employment in 

 the construction of new mounds. 



I had hoped with the above data of annual growths, and the dimen- 

 sions of a number of hills, to obtain by a simple calculation and with 

 reasonable accuracy, the age of any hill. But I am compelled to 

 abandon this hope by the fact that the largest mound reported at 

 Pine Hill, the largest of which I have knowledge, having a cubic 

 contents of about 300 cu. ft., is built upon an old charcoal hearth. 

 It is therefore of quite recent date. The upbuilding of such a cone 

 within so limited a period indicates an immense capacity ior accom- 

 plishing work under certain favorable conditions. While the above 



