326 DIBECTIOVS FOR THE MICROSCOPE. 



METHOD OF USING THE MICROSCOPE. 



In using the microscope there are three things necessary to be con- 

 sidered; 1st, Tiie preparation and adjustment ot" the instrument it- 

 solf. 2dly, 'J'he proper quantity of hght, and the best method of di- 

 recting it to the object. 3dly, The method of preparing the objects, 

 so that their texture may be properly understood. 



Preparation off/ic instrument. — 1st, With regard to the microscoj^e 

 itself, the first thing necessary to be examined is, whether the glasses 

 are clean or not; if they are not so, they must be wiped with a piece 

 of soft leather, taking care not to soil them afterwards with the lingers; 

 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 

 fall 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 be brought as near the centre of 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; but 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 be determined about them without making the proper 

 allowances; and different lights and positions will often show the 

 same object as very difterent from itself. There is no advantage in 

 any greater magnifier than such as is capable of showing the object 

 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 une another, may give reflec- 

 tions very difierent from what they would if seen by the naked eye. 

 Some consideration is likewise necessary in forming a judgement of 

 the motions of Jiving creatures, or even of fluids, when seen through 

 the microscope ; for as the moving body, and the space wherein it 

 moves, arc magnified, the motion will also be increasetl. 



