158 



THE AMERICAN NATURALIST 



[Vol. XL 



is a detailed study of southern Wisconsin and northern IlKnois. The 

 report is fully illustrated by maps, representing the successive stages 

 in the deglaciation of the district. 



PubUration 101 of the Field Columbian Museum, entitled "The 

 Ilodeo Meteorite" by O. C. Farrington, is a description of a medium 

 octahedrite with high phosphorus content, weighing about one hun- 

 dred pounds. The mass was found in 1852, in the State of Durango, 

 Mexico. 



A series of experiments which aim to give some quantitative values 

 for the pressures exerted by growing crystals, has been performed 

 by G. F. Becker and A. L. Day. In these experiments, it has been 

 proved that crystals increase most rapidly on their under surfaces, 

 and thus lift the earlier formed portions. So energetic is this action 

 that a kilogram weight was raised several millimeters by an alum 

 crystal whose bearing surface was only a small fraction of a square 

 centimeter. The force, therefore, is believed to be of the same order 

 of magnitude as the resistance that crystals offer to crushing. The 

 published account of these experiments appears in the Proceedings 

 of the Washington Academy of Sciences, vol. 7, pp. 283-288. 



(No. 469 was issued January 20, 1906) 



