Polytechnic Association Proceedings. gl3 



cent greater surface than the other, and after eleven houi-s of simi- 

 lar contact the rod was ground aw.iy one-quaii;er of an inch — tho 

 value of the stones being as one to thirty-three. From an examina- 

 tion of specimens of this stone on exhibition in New York, we are 

 forced to believe this report is greatly exaggerated. 



THE POTATO. 



Mr. George May, of Benthall, England, in his prize essay on the 

 potato, gives the results of experiments on 129 trial plots, which 

 may be summed up as follows: 



1. Every increase in the size of the set, from one ounce to eight 

 ounces in Aveight, produces an increase in the crop much gi'eater 

 than the additional weight of the set planted. The net profit, over 

 and above the extra weight of sets, in planting four ounce sets in 

 lieu of one ounce sets, amounted, on the whole series of experi- 

 ments, to between three and four tons per acre; and the fmther 

 profit, on the increase of the size of the set from four ounces to 

 eight ounces, averaged about five tons per acre, all the intermediate 

 steps partaking proportionately of the increase. 



2. The advantage of large sets is more marked in the late than 

 in the eai'ly varieties. 



3. In the use of small sets, of from one to three ounces in weight, 

 a large balance over and above the weight of the sets was obtained 

 by planting from six to nine inches apart in the rows than at wider 

 intervals. 



4. Increasing the intervals at which the sets are planted, even of 

 the largest size, in the rows, to more than twelve inches, diminishes 

 the crop, and the wider intervals induce no iuerease in the weight 

 of the produce of the individual sets. 



5. It may be broadly stated that the weight of the crop is pro- 

 portionate to the weight per acre of the sets, and that small sets 

 will produce the same crop as an equal weight per acre of large 

 sets. The fact is, however, of limited application, tw a weight of 

 very small sets, equal to a weight of full sized potatoes, could not 

 be got into the ground, except by planting them so close as to be 

 prejudicial to the crop. The advantage, therefore, of large sets 

 remains practically unimpaired. 



6. "Weight for weight cut sets produce as nearly as possible the 

 same weight per acre as whole potatoes, but, for the reasons given 

 above, the weight of the sets should not be reduced by subdivision. 



