326 uiRECTJOxs roll the microscope-. 



METHOD or USING THE MICROSCOPE. 



In using the microscope there are three things necessary to l)e con- 

 sidered; 1st, The preparation and adjustment of the instrument it- 

 self. 2dly, 1'he proper quantity of Hght, and tlie best method of di- 

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

 so that their texture may be properly understood. 



Prcpcu-ation 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 are not so, they must be wiped with a piece 

 of soft leather, taking care not to soil them afterwards witli 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 

 fall upon the glasses, nor to hold that ])art of the body of the instru- 

 ment where the glasses are jilaced with a warm hand ; because, thus, 

 the moisture, expelled by the heat from the metal, will condense upon 

 the glass, and j)revent the object from being distinctly seen. The olj- 

 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 fmuid where the largest field and most 

 distinct view of the object are to be had ; but every person ought to 

 adjust the microsco}>e 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 anin'.al ought to be as 

 little hurt or discomposed as possible. 



GrcKt caution is to be used in fojming 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 different 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 one another, may give reffcc- 

 tions very different from w hat 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 it 

 moves, are magnified, the motion will also be inc-reasctl. 



