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DIRECTIONS FOR TIIE MICROSCOPE, 
METHOD OF TJSING THE MICROSCOPE. 
Iii using the microscope there are three things necessary to be con' 
sidered; 1st, The preparation and adjustment of the instrument it- 
self. 2dly, The proper quantity of light, and the best method of di- 
recting it, to the object. Sdly, The method of preparing the objects, 
so that their texture may be properly understood. 
Preparation of the instrument. — 1st, With regard to the microscope 
itself, the first thing necessary to be examined is, whether the glasses 
are clean or not; if they arc not so, they must he wiped with a piece 
of soft leather, taking care not to soil them afterwards with the fingers ; 
and, in replacing them, care must be taken not to place them in an 
oblique situation. We must likewise be careful not to let the breath 
tall upon the glasses, nor to hold that part of the body of the instru- 
ment where the glasses are placed with a warm hand ; because, thus, 
the moisture, expelled by the heat from the metal, will condense upon 
the glass, and prevent the object from being distinctly seen. The ob- 
ject should he brought as near the centre ol the field of view as pos- 
sible, for there only it will be exhibited in the greatest perfection. The 
eye should be moved up and down from the eye-glass of a compound 
microscope, till the situation is found where the largest field and most 
distinct view of the object are to be had ; hut every person ought to 
adjust the microscope to his own eye, and not depend upon the situa- 
tion it was placed in by another. A small magnifying power should 
always be begun with ; by which means the observer will best obtain 
an exact idea of the-situation and connection of the whole, as well as 
the connection and use of the parts. A living animal ought to be as 
little hurt or discomposed as possible. 
Great caution is to be used in forming a judgement on what is seen 
by the microscope, if the objects are extended or contracted by force 
or dryness. 
Nothing can he determined about them without making the proper 
allowances ; and different lights and positions will often show the 
same object as very different from itself. There is no advantage in 
any greater magnifier than such as is capable of showing the obje ct 
in view distinctly; and the less the glass magnifies, the more plea- 
santly the object is always seen. 
The colours of objects are very little to be depended on, as seen by 
the microscope ; for their several component particles being by this 
means removed to great distances from one another, may give rede 0 ' 
tions very different from what they would if seen by the naked eye. 
Some consideration is likewise necessary in forming a judgement of 
the motions of living creatures, or even of fluids, when seen through 
the microscope ; for as the moving body, and the space wherein h 
moves, are magnified, the motion will also be increased. 
