172 



MICROSCOPIC OBJECTS. 



It may be remarked that the various kinds of composi- 

 tion candles which consume their own snuff are very bad 

 for microscopic purposes except the bat's-wing kind. In 

 the other sorts the two wicks revolve, and thus present 

 an unequal quantity of hght in a given direction ; some- 

 times the two wicks being presented edgewise to the 

 object, at other times standing in a hhe. 



It is sometimes advisable to shade the Hght from the 

 surrounding objects. In this case a copper tube with a 

 small aperture in its side may be made to fit over the 

 flame. We must now use the flame of a lamp, as a 

 candle would melt in such a situation. If a candle be 

 preferred, then a shade attached to an arm may be 

 employed. 



