Presidential Address. By A. ID. Michael. 99 
ments nor makers’ names, but possibly some of my bearers will not be 
slow to guess what it is. The others have all ceased to hold the focus 
after a time, and although the tightening of the screws intended to 
remedy this will cure matters temporarily, it soon ceases to do so. 
Then the instrument goes back to the makers, and returns better, but 
not as good as it was at first, and the period for which it will retain 
its improvement gets shorter and shorter. Why is this ? It will be 
said, “ from the natural tendency of all things to wear out.” This is 
quite true ; but the oldest instrument does not wear out, or, at all 
events, only very little ; therefore I may repeat the question, Why is 
this ? Ami entirely wide of the mark in suggesting that possibly 
better workmanship and harder metal may have something to do with 
it ? It appears to me that in the struggle to reduce cost we forget 
the great importance of having the working parts made of the most 
enduring, and consequently, as a rule, the hardest, metal possible. 
The balance wheel of a watch has a pivot of the hardest steel pro- 
curable, and it rests upon something equally hard ; but have we 
followed this excellent example ? I fear not ; cost has come in the 
way, and although the pinion of our coarse-adjustment is usually, I 
imagine, made of steel, yet the rack is made of something, not only 
softer, but often very considerably softer. The harder metal naturally 
wears away the softer to some extent, and after a period of use the 
teeth or screw of the pinion which fell sweetly into the rack at first 
do not quite do so any longer ; then comes increased wear, and the 
evil goes on even faster than before ; moreover, it seems to me that 
diagonal racks wear as fast as straight ones. It is true that the rack 
may usually be replaced at some considerable expense and trouble, but 
it is desirable to avoid this if possible, and a good deal of incon- 
venience is usually put up with before deciding to change the rack. 
It is not the rack alone that wears ; the shaft that carries it wears 
away also, and the softer it is the faster it wears. Fine instruments 
are made commonly with the parts near the angles slightly project- 
ing, the central part being planed away. This is doubtless the best 
construction, but it does not wholly cure the evil unless the metal be 
very hard and highly finished ; the projecting part wears, and what 
is worse, it wears unequally. At least nine-tenths of each man’s work 
is usually upon a small part of the rack, according to the objectives he 
most frequently uses, and the parts which receive the pressure when the 
Microscope is in this position wear most. There must always be a portion 
of the shaft and rack which is above the collar of the stand when the 
instrument is in use, and therefore does not wear at all ; thus the 
projecting angles, although they project equally all the way along at 
first, gradually cease to do so ; this is a much worse evil than the 
rack, for it produces an uneven motion and a difficulty in holding the 
focus ; and these angles are usually of the same piece of metal as the 
shaft itself, and cannot be replaced. It seems to me that where these 
projecting angles exist, as it is desirable that they should do, they might 
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