12'8 



Microscopical Essays, 



Of the necessary Preparation of the Microscqpe 

 for Observation. 



We have in the laft chapter explained thofe particulars that 

 conflitute the difference of one microfcope from another, and 

 fhewn how each inftrument is to be ufed, and how the feveral 

 parts are to be applied to it. We mall now proceed to give feme 

 general directions applicable to every microfcope. The obferver 

 is therefore fuppofed to have made himfelf mailer of his inftru- 

 ment, and to know how to adapt the different parts of the appa- 

 ratus to their proper places. 



The firft circumftance neceflary to be examined into is, 

 whether the different glades belonging to the microfcope are per- 

 fectly clean or not ; if they are not clean, they muff be taken out 

 and wiped with a piece of wafh leather, taking care at the fame 

 time not to foil the furface of the glafs with the fingers : in re- 

 placing the glafles, you muff alfo be careful not to lay them in 

 an oblique fituation. i 



The object fhould be brought as near the center of the field of 

 view as poffible, for there only will it be exhibited in the greater! 

 perfection. 



The eye fhould be moved up and down from the eye-glafs of 

 a compound microfcope, till you find that fituation where the 

 largeft. field and mod diftinct view of the objecT: is obtained. 

 Every perfon ought to adjuft the microfcope to his own eye, and 

 not depend upon the fituation it was placed in by another.' 



Care 



