284 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1926 
ordinary methods of rock microscopy had to be replaced by special 
tests. By these means it was possible definitely to identify quartz, 
biotite, orthoclase and plagioclase feldspar, hornblende, carbonate, 
kaolinite, and apatite in approximately that order of abundance, 
together with some grains of one or two other minerals which, in 
the absence of means for making further more delicate tests, could 
not be determined with certainty. If allowance is made for the 
fineness of grain of clay, of which a relatively large percentage 
would fall below the minimum size determinable, the kaolinite might 
perhaps stand a little 
higher on the list in an 
analysis of the total mate- 
rial. To the naked eye this 
sample has a somewhat un- 
usually high biotite con- 
tent. 
In connection witha 
more extended piece of re- 
search from a _ different 
point of view, Prof. W. C. 
Lowdermilk has analyzed 
loess-soil material from 
Shensi in the department 
of forestry, University of 
Nanking. Professor Low- 
ic. 2.—Grains of loess from Honan (magnified 104 dermilk has nee ener 
times). The graduations on the cross wire indi- ously placed his prelimi- 
cate one-tenth millimeter nary results in my hands. 
The mechanical analyses were carried out using two samples from an 
uncrushed block of loess from Liu-lin on the Red Cross Road near the 
Yellow River. 
Sample 1: Per cent 
(a) Percentage of sand and silt by settling__-___ SPR PRREeE MD, ALOE coe 80. 01 
PET CONEREE OL CU ea ye ie a ape ae 19. 46 
VV ar a0) ea aie Aad eof uel lesa ah, EP NES ab SE SL yoni te aE os 2 2 ag ln 5D 
100. 00 
(b) Sieve study: 
Grains over 0.1 millimeter diameter______________________- 2,15 
Grains under 0.1 millimeter diameter____________________- 97. 85 
100. 00 
(c) Micrometer study: 
Class Average diameter of particle 
mes Sar GE Peers cee Ree ane g i kee NE 0.13 millimeter 1.59 
VERY t fine (Same edt eels es ee ae Pe ee .065 millimeter 27.44 
SH PE RN EGA so, ESA A TESS ae .033 millimeter 50.97 
CES a pe a le ene us Rid Re Bal aaa EA YE ie .0035 millimeter 20. 00 
WORPOT ooo eS ced ee es ed .10 
