158 NATURAL HISTORY MISCELLANY. 
tions of the ear ate and verte the moraines which they have 
left as evidence of their former extension are often large and conspic- 
uous, they are Aarni i: comparison with the detrital masses 
formed by aqueous erosion. There is nothing anywhere in California 
which indicates a general glacial epoch during which ice covered the 
whole country and moved bodies of detritus over the surface, inde~ 
pendently of its aegis configuration, as is seen throughout the 
North-eastern Sta 
he same aan of things prevails in Nevada and through Ore- 
on, as far as explored by the members of the Survey. The detritus 
seems always to be accumulated at the base of the mountains — gravel, 
boulders, and sand lying below and not far distant from the bed of rock 
of which these materials once formed a part, and from which they ap- 
pear to have been detached by weathering and aqueous erosion. 
From the observations of Messrs. Ashburner and Dall, it would ap- 
pear that no evidences of Northern Drift have yet been detected on 
this coast, even as far north as British Columbia or Russian America, 
ee of ep gentlemen have observed any indication of a transport- 
o the north towards the south, or of any 
ns tall of ctor similar to that which must eee existed in the 
Eastern States during the diluvial epoch. oe of the Califor- 
nia Academy of Natural Sciences. 1866. Vol 3, part iii 
a ooo 
MICROSCOPY. 
TEST OBJECTS FOR THE Microscorpr.—To such wonderful perfec- 
tion has this process been rents that M. Nobert, of Griefswald, in 
Prussia, has engraved lines upon glass so close together, that upwards 
of eighty thousand would go in the space of an English inch. Several 
series of these lines were engraved upon one slip of glass. By these 
the defining power of any object-glass could be ascertained. As test 
objects, they are equal to, and even rival, many natural objects which 
1-50,000th of an inch, while the finest lines engraved by M. Nobert are 
not more than the 1-100,000th of an inch apart. 
Podura : j most excellent “test object.” According to 
subtillissima and Hya- 
