38 Cincinnati Society of Natural Firstory. 
One great cause of failure among amateurs I think comes from a 
lack of knowledge when to cease development, and that too when 
exposure is pretty nearly correct. In this matter, as in the matter 
of exposures, no hard and fast rule can be laid down, by whica 
success will be assured. Different makes of plates present differ- 
ent appearances at the same stage of development, so I would 
recommend that one brand of plates be used as exclusively as 
possible. I know of no better way of learning when a plate has 
been sufficiently developed, than to make an exposure on a row of 
buildings all alike, let them cover the ground glass from one side 
to the other. After inserting your holder, draw the slide out, say 
one-quarter of its length, uncap your lens, and give, say, two 
seconds exposure; recap the lens and draw your slide again, this 
time half way out, uncap and expose for another two seconds ; 
repeat this operation again, draw the slide out three-fourths of its 
length, exposing it as before, and again draw it entirely out, giving 
the same exposure. The first quarter of the plate will then have 
eight seconds exposure, the second quarter six seconds exposure, 
the third quarter four seconds exposure, and the last two seconds 
exposure. Develop this plate with your normal developer until in 
the center of the plate you find you have plenty of detail in the 
shadows, with sufficient density; wash thoroughly, fix and dry; 
you will now have a plate which in all probability is in one 
part under-exposed, and in another part about correctly exposed, 
and in another part over-exposed, and consequently you have an 
illustration of under-development, correct development, and over- 
development. Makea print from this, then sit down and study 
both print and negative. The under-exposed part will present 
a lack of detail in the shadows and a thin, transparent neg- 
ative. Over-exposure will be shown by an abundance of detail, 
but a plate thin with a general foggy appearance. The over-devel- 
oped portion will show detail all out, but too dense and strong, 
while the under-developed will show a clear but weak negative, 
with considerable detail, which would have been improved by 
longer development. 
It is oftentimes a difficult matter to tell whether a plate has been 
over-exposed or under-developed, but as a rule I think amateurs 
are more apt to err on the side of over-exposure, rather than under- 
development. Now if you will make three or four exposures at 
the same time and under the same conditions as this one was made, 

