THE AMERICAN MONTHLY 



I January, 



light from the flame is passed through a ground glass or blue glass at 

 pleasure, and before reaching the bull's-eye. Strong or faint light, 

 direct or oblique light, can all be had easily and without changing any 

 adjustment of the microscope. The half-inch wick gives a very good 

 flame, kerosene being used to burn. The arrangements for draft and 

 for cleaning are good. More and better effects can be gotten with this 

 lamp than with any other that has come to our notice. The placing 

 of the lamp on the market will be duly advertised at the proper time. 

 II. — Zentmaykr's Dissecting Microscope. 



(See frniitispiece, figure II.) 



This instrument was made primarily for botanical w^ork. It has a 

 circular base 5 inches in diameter and is made of polished brass. A 

 stout pillar rises about 6 inches on one side, to which are attached a 

 broad stage (4x5 isi.) and a jointed arm for carrying the lenses. A 

 plane mirror is adjusted to the base beneath the stage. The stage car- 

 ries spring clips, which are easily removed to make room for a glass 

 plate which fits the well of the stage. With the instrument come tw^o 

 lenses, i inch and f inch, which may be combined to secure a § 

 inch focus. The plan of this microscope was suggested by Prof. J. T. 

 Rothrock, of the University of Pennsylvania, and it is used in his 

 botanical classes. The cut is one-half the natural size. The whole is 

 packed in a neat walnut case with drawer and handle. The price is 

 eight dollars. 



III. — Koch's and Woi.z' Microscope Lamp. 



This lamp consists of a plain, round- 

 burner, kerosene lamp, mounted on a stand 

 so that it can be raised and lowered ; it is 

 covered with a chimney of japanned sheet- 

 iron with two tubulations on a level with 

 the most luminous part of the flame, each 

 holding a solid glass I'od of peculiar 

 curvature. The' light entering one end of 

 the glass rod is transmitted through its full 

 length, without radiation through the sides 

 of the rod, and it emanates at the other end 

 diftiised and soft with almost undiminished 

 intensity. A double bent rod is intended 

 for illuminating transparent objects from beneath the stage ; the other, 

 with but a single bend, is used for illumination of opaque bodies from 

 above. 



The following are some of the advantages claimed for this lamp : 

 It can be used in a dark room or at night, making the observer inde- 

 pendent of daylight. The light can be brought very near to the object, 

 and it is dift'used and uniform. This is especially the case where the 

 object is imbedded in or forms cavities. Shadows, which cause error 

 where a high magnifying power is used, are entirely avoided. The lamp 

 is covered by the metallic chimney, and as the rod transmits no rays 

 laterally, the eye is not annoyed by any direct light. The lamp is com- 

 plete in itself, and makes other auxiliaries, such as mirrors, condensing 

 lenses, etc., superfluous ; or these may be rendered more efficient by its 

 aid. It therefore forms a useful adjunct to the plainest or the most 

 complicated microscope. It is very simple in construction, and easily 

 adjusted, requiring no particular care or skill. 



