THE MICROSCOPE. 27 



d, adjusts the lens to the focus of the object, either on g or h. 

 But the chief merit in its construction consists in a concave 

 speculum or mirror of silver, &, highly polished, to the centre 

 of which, at Z, the magnifying glass is adapted. This is screwed 

 into the ring i, and so held that a bright light, as from a can- 

 dle or white cloud, is received upon the speculum (called a 

 Lieberkuhn, from the name of its inventor). The light so 

 received is concentrated upon the object, which is brightly 

 illuminated; and is adjusted to the focus of the lens by turning 

 the nut d. 



For minute dissection of animal or other tissues, which is 

 generally performed under water, as hereafter described, the 



Fig. 5. 



microscope of Mr. Slack, with the improvements of Dr. H. 

 Goadby, F.L.S., is the most efficient. The following is a de- 

 scription of the instrument employed by the latter gentleman 

 in his microscopic researches ; and with which he has made a 



