82 



PROCEEDINGS OF THE CHICAGO MEETING 



very inucli more coinniou phe- 



coarse grains, although not invariable, is a 

 nomenon than in the spring.^ 



lu cut number 4 there is shown a section of till from the drumlin called 

 Winthrop Head, in Boston Harbor. The magnification in this case is about 40 

 diameters. On tlie left is a pebble ; then comes a crack separating this pebble 

 from the matrix on the right. The finest material is a da's'. A microscopical 



Figure 4. — Section of Till from the Drumlin, called Winthrop Head, Boston Harbor 



examination of this till matrix gives the following minerals in the order of 

 their importance : sericite, quartz, orthoclase, microcline, microperthite, oligo- 

 clase, andesine, biotite (?), hornblende, and olivine. Some of the feldspar is 

 much altered, showing liaolin. The olivine also shows much alteration. The 

 structure of the till needs no explanation. 



With this method of hardening soft materials for grinding, it should be pos- 

 sible to examine annual deposits now forming, and thus to obtain some idea 

 of the difference between our present seasons and the seasons of Pleistocene 

 and earlier times. 



jSIETAMORPHWM in METE01UTE8 

 BY GEORGE P. MERRILL 



{Abstract) 



The paper gives the results of studies tending to show that the crystalline 

 chondrites as well as stones of the white gray and intermediate groups origi- 



^ R. W. Sayles : Seasonal deposition in aqueoglacial sediments, 

 seam of Comparative Zoology, vol. slvii, no. 1, 1019, p. 49. 



Memoirs of tlie Mu- 



