NOBERT’S TEST PLATE, ETC. 93 
carcasses of some huge whales brought in to land since his 
departure. 
The moon rose full and round, but waned rapidly as she 
neared the zenith. A fine’eclipse took place which was 
almost total. Crowds gathered on the shore to watch the 
moon’s* fading light. The Americano ought to be able to 
explain it. He is applied to. Whereupon, by the light of an 
antique oil-lamp in a store near by, with a big earthen water- 
jar to personate thé earth, and a smaller one the moon, a 
lecture on the theory of eclipses was delivered to an appre- 
ciative audience, with heaven’s blue dome for a chart. 
Next day a few hundred weight of whales’ bones were 
added to our freight, and we moved up stream. The tiled 
roofs and white walls and cocoa palms of Caravellas came in 
view, Jaco blew his horn, and, in a few moments, with the 
rattle of the chain from the bow, the Cruise of the “Abrol- 
hos” had ended. 

NOBERT’S TEST PLATE AND MODERN MICROSCOPES. 
BY CHARLES STODDER. 
Every possessor of a first-class microscope wishes to 
know what his instrument is capable of doing. To the prac- 
tical worker it is a matter of much importance, for when the 
utmost power of his instrument is exhausted, he will know — 
that it is a waste of time to endeavor to see more. One 0 
the desirable and important properties of a microscope is the 
power to show or “resolve” very fine lines grouped together, 
e. g. the striation of the frustules* of the diatomacee. For 
the purpose of testing the resolving power of the micro- 
scope, the lines ruled on glass by F. A. Nobert, of Barth, 

*A frustule (Z. frustrum, a fragment) is one of the fragments into which diatoms 
Separate. 

