84 NATURALISTS’ ASSISTANT. 
joints of the apparatus enable a person to raise and depress 
the lens and still keep it horizontal. ‘The end portion con- 
sists of a piece of brass tube with a slot cut in it to receive 
the cover of the lens. Such an instrument can be made for 
two dollars at the most, and to all intents and purposes will 
serve instead of a dissecting microscope, all forms of which are 
more or less inconvenient. When it is desirable to use trans- 
mitted light, the watch glass or other transparent dish may be 
placed in the mouth of a bottle and thus sufficient light for 
all ordinary purposes can be obtained. 
Dissecting microscopes are advertised by all dealers in 
microscopic goods, but they are but little used by professional 
naturalists, a triplet with a stand answering all their purposes 
and that with few of the many objections which they all 
have. , 
The compound microscope is next to be considered. — In 
this instrument an inverted image is formed by the lens 
(or combination of lenses) nearest the object (called the 
object glass) and viewed by the other lens nearer the eye 
(the eye-piece or ocular). These lenses are mounted in a 
tube fitted with appliances for bringing them nearer to or re- 
moving them farther from an object placed on the stage. 
Suitable methods are also employed for illuminating the ob- 
ject, and a stand to support the whole completes the list of 
necessary portions. ‘These will now be taken up in order and 
their various requisites discussed. In this the writer is well 
aware that the views advanced are in direct opposition to 
those held by many mzcroscopists, but he is also aware that 
they are in almost full accord with the opinions of those who 
