250 C. G. DUNNING ON A NEW FORM OF LIVE BOX. 



The lower plate, or trough proper, is made of metal, or 

 some other suitable material, 3 inches long, 1| inches wide, and 

 about t ! q- inch thick, with an oval or oblong perforation in the 

 centre, and the under-side is recessed as indicated by the dotted 

 lines. In this recess is fixed by means of Canada balsam, or 

 shellac, a piece of stout covering glass, forming the bottom 

 of the cell ; the recess being sufficiently deep to prevent the 

 thin glass bottom from coming into actual contact with the 

 stage of the microscope, or with the table when it is not in use. 

 Two pins are provided near the bottom edge of the cell. 



The cover (Fig. 14) is formed of a piece of thin brass 

 rather shorter than the trough, but about the same width ; 

 it has an opening formed in it to correspond with that in the 

 trough, and under this opening is cemented a piece of cover 

 glass. The cover plate is notched out at the two bottom 

 corners, and at the two top corners are formed a couple of pro- 

 jecting ears. 



In order to use this apparatus it must be laid flat upon the 

 table, and filled quite full of water. The object to be examined 

 is then placed in the cell, and maybe properly arranged therein ; 

 the cover is then lowered gently down, the two notches at the 

 bottom edges being first placed against the pins ; in this way 

 the superfluous water will be driven out, and the whole 

 apparatus may be wiped dry. The capillary attraction, 

 assisted by the weight of the cover, will be found sufficient to 

 prevent any leakage ; and the pins at the bottom prevent the 

 cover from sliding down when the microscope is inclined. 



Although there is, of course, no supply of air, I have had 

 Vorticella, zoophytes, &c, under observation for more than two 

 hours at a time, without any change or renewal of the water ; 

 but even if it should be deemed necessary to introduce a fresh 

 supply, it can easily be done by carefully lifting the cover by 

 the two ears at the top, and making the addition by the aid of 

 a pipette. 



The apparatus is intended more especially for use as a 

 shallow cell, with moderately high powers, but its depth may 

 be readily increased by means of an intermediate trough, either 

 of metal or ebonite, which may be inserted between the trough 

 and the cover, and will be found to be quite free from leakage. 



The area of the cell as above described is rather large, as 



