304 PROF. WILLIAMSON’S ADDRESS TO THE 
necessary, whilst our time for original inquiry is more 
limited by the necessity of reading and searching out 
what has already been done by other men. 
Microscopic inquiry involves two processes which are 
essentially distinct, namely, the observation of facts, and 
their interpretation, I would earnestly recommend you 
to begin by disciplining yourselves in the observation of 
facts, ever honestly recording what you see. This is not 
by any means so easy a task as may at first sight appear ; 
for we frequently find ourselves at a loss to distinguish 
facts from mere appearances. An illustration of my 
meaning presents itself in the case of the Navicule: How 
long were microscopists disagreed as to whether the dotted 
lines sculpturing their siliceous cases were due to eleva- 
tions or depressions? Could the microscope but be made 
stereoscopic, much of this difficulty would be removed. In 
estimating the forms and relative positions of objects in a 
surrounding landscape, man derives his conclusions from 
two sources — from the indications afforded by linear and 
aerial perspective, and from the adjustment of the visual 
angle to objects at various distances. In working with 
the microscope, all the aids derivable from perspective are 
unavailing, from the nearness of the object and the almost 
uniform plane of all that can be brought within the focus of 
the microscope ; and as the instrument is essentially mono- 
cular, we are equally deprived of the aid which the visual 
angle would afford us; hence, being deprived of both our 
ordinary means of measuring distances, we are compelled 
to fall back on more doubtful methods of estimating them. 
This circumstance demands that the microscopist should 
be strictly conscientious ; that he should never assert any- 
thing to be a fact, whilst the slightest doubt remains in 
his mind respecting it. By so doing he would save much 
needless labour to others, who now have to go over the 
same ground, and furnish their confirmation, before the 
SESS 825. dk. 
