204 



THE AMERICAN MONTHLY 



[November, 



single lens of that focal length to 

 magnify lo diameters. Of course the 

 value of such an arrangement depends 

 on its authority. The table was made 

 for my personal convenience, and I 

 send it solely for the purpose of 

 giving a better idea of what I have in 

 mind. 



A tube of standard length (ten 

 inches) and a 2-inch eye-piece are to 

 be used in all cases where this table is 

 referred to. 



-o— 



W.M. 



Kotary Object Carrier. 



BY J. M. FLINT, SURG. U. S. N. 



The following described device for 

 exhibiting a series of mounted mi- 

 croscopic objects, without the incon- 

 venience of a change of slides, 

 though probably not entirely new 

 (few things are so) , is yet original 

 so far as the writer is concerned, and 

 has been found efficient in practice. 

 As described it is arranged for show- 

 ing foraminifera. which are viewed 



as opaque objects, with a low power. 

 The selected foraminifera arc 

 mounted on small brass disks fur- 

 nished with a stem, by means of 

 which they may be carried in a 

 *■ Beck's disk holder ' when it is 

 desired to make a thorough study of 

 the specimens. 



Ordinarily these disks are inserted 

 in thin wooden slides of regulation 

 size and kept in the usual boxes made 

 for the purpose, until the series is 

 complete or ready for transfer. In 

 order to protect the specimens from 

 dust or injury, and at the same time 

 maintain their accessibility, movable 

 covers are constructed ancl secured as 

 follows : — A score or more of curtain 

 rings, not flattened, are slipped upon 

 a squared rod of wood, and brushed 

 over freely with thick shellac. On the 

 following day, before the shellac has 

 become hard, the rings are slightl)' 

 separated in pairs. When the pairs 

 are firmly united, a thin glass cover 

 is secured to the upper surface of 

 each pair, and thus a little box cover 

 is formed, deep enough to enclose 

 disk and specimen. Now, by driv- 

 ing two small gimp tacks into the 

 wooden slide, at the proper distance 

 apart, and deep enough so that the 

 heads of the tacks will just enter the 

 groove between the rings, a simple 

 catch is formed, by means of which 

 the cover may be secured, and also 

 be removable at pleasure. 



For exhibition — and for co\ enience 

 of reference as well — these disks, 

 bearing the specimens and the cov- 

 ers, are transferred to a thin circular 

 plate six inches in diameter, in this 

 case made of three or four sheets of 

 card-board glued one upon the other. 

 This makes a firm plate, not liable 

 to warp, and in which holes may be 

 readil}' bored for the insertion of the 

 disks, and the tacks driven to secure 

 the covers. By inserting the disks 

 as near the edge of the plate as pos- 

 sible, a line fifteen or more inches in 

 length is obtained on which to disjola}- 

 the objects. The circular plate bear- 

 ing the specimens as abovx, is made 



