POWELL AND LKALAND S MICROSCOPE. 



179 



will be observed there are two notches in the plate, capable of admitting 



the two springs on the condenser ; put it in, and turn 



it till the milled head is in the best position for use ; 



bring your object into focus, and adjust the condenser 



till you see distinctly the image of the lamp, or the 



frame of the window, if by daylight ; and then you 



may be assured the most intense light is obtained, which 



is not always desirable. The light is lessened or 



diminished by turning back the condensing lens, by 



means of the milled head. 



Fig. 2. 



FIG. 3. Micrometer for measuring objects. The upper part of the 

 stage is taken out of the plate, put into the micro- 

 meter, and the whole put again on to the stage. To 

 measure an object, observe that the micrometer 

 stands at nought ; then adjust one edge of the 9b- 

 ject till it comes in contact with the web in the eye- 

 piece, by the milled head C ; then adjust it across 

 by the head of the micrometer D, when the number 

 of revolutions and points may be taken. 



FIG. 4. Plate on which 

 Frogs or Fish are tied to 

 examine the circulation of 

 blood in the vessels. 



FIG. 5, Large Stage, used 

 when the Frog Plate is used. 

 To examine the circula- 

 tion of the blood in the web of 

 the foot of the frog, or the tail of 

 a fish, it must first be enclosed in 

 the bag ; then fastened on the plate 

 by the holes in either side of it ; 

 then tie some thread to about four 

 of its toes, and spread the web out 

 by fastening the ends through the holes in the plate. 



Fig. 6. 



FIG. 6. Phial holder for viewing Chara, %c. while in a living state. 

 It is adapted to go in the plate of the stage, and is put in after taking 

 the upper part of the stage oft*. 



N 2 



