506 Scientific News. [ June, 
MICROSCOPY. 
Test Osjects. AMPLIFIER.—Why I think little of the Podura 
as a test, is, that it requires a skilled microscopist to appreciate it 
for that purpose, anda skilled microscopist can judge of the value 
of a lens by its performance on any object. Test-objects are of 
most use to a beginner, and if he does not know exactly what he 
ought to see, a skilled showman can make them both a delusion 
and a snare. 
World of Science. 
10: 
SCIENTIFIC NEWS. 
— Dr. James Lewis, the well-known conchologist, died of apo- 
Massachusetts, from 1849 to 1851 that he became interested in 
his favorite science and formed the nucleus of what was to via 5 
one of the most valuable private collections of American lan 
and fresh-water shells extant. From that time untila year or tW° 
previous to his death, he was a most devoted student and untiring 
enthusiastic collector. He is widely known to the authorities 
the science he cultivated by a very extensive correspondence, ° 
which art Dr. Lewis was certainly a master. Within the mer” 
of his acquaintance are embraced all the living names familiar 
to the younger naturalists, and many others who have ‘ 
away. His published works, when the magnitude of his labor: 
