Microscopical Essays. $£ 



Fig, 3. Plate VI. reprefents that which was ufed by M. Lyon- 

 net for differing the coffus. 



Fig. 1. Plate VII. B. The aquatic microfcope ufed by Mr, 

 Ellis for investigating the nature of coralline, and recommended 

 by Mr. Curtis to botanifts, in his Flora Londinenfis. 



Fig. 1. Plate VI. A botanical microfcope, contrived by Dr., 

 Withering. 



Fig. 2. Plate VI. A botanical microfcope, by Mr. B. Martin. 



Fig. 5. Plate VI. The tooth and pinion microfcope, which i$ 

 now generally fubftituted in the room of Wilfon's. 



Fig. 8. Plate VIII. A botanical magnifier. 



Fig. 7. Plate VIII. A different kind of botanical magnifier. 



A compound microscope, as it confifts of two, three, or 

 more glafles, is more eafily varied, and is fufceptible of greater 

 changes in it's conftruelion, than the fingle microfcope. The 

 number of the lenfes, of which it is formed, may be increafed or 

 diminiihed, their refpeclive pofitions may be varied, and the 

 form in which they are mounted be altered almoft ad infinitum, 

 But among thefe varieties, fome will be found more deferving of 

 attention than others ; it is of thefe only we fhall fpeak in this 

 place 



The 



