IIo THE NORTHERN MICROSCOPIST. 
there are yet many new species to discover. Here then, is a wide 
field for activity and enterprise ; and we can promise that it is as 
full of delight and interest as it is wide. But, the morphology, 
chemical nature, and the relation of Lichens to the atmospheric 
medium, are yet to investigate. Researches in these departments 
have been begun, but that is all. These deeper subjects of study 
though, can only present themselves properly to the mind of the 
student, when he has mastered the primary elements, and learned 
readily to distinguish one plant from another. 
LANTERN TRANSPARENCIES OF MICROSCOPIC 
OBJECTS. 
N the preparation of transparencies for the lantern it is necessary 
first of all to secure a good sharp negative ; this is placed above 
another gelatine plate (preferably Wratten & Wainwright's ordinary 
—not instantaneous) and exposed for a moment to the light ; the 
latent image is then to be developed and fixed in the usual manner, 
after which it may be toned with platinum to improve the color of 
the deposit. 
Transparencies for the lantern may also be prepared by means 
of the autotype process upon carbon tissue. They have to be 
manipulated with much care, and the operator should follow the 
instructions which have been laid down by the Autotype Co. in 
their shilling manual. Thus :— 
“In order to secure the necessary vigour and clearness to 
produce a brilliant picture when thrown upon the screen, a paper 
is required having a quantity of very fine opaque pigment—this is 
provided by the Company’s special transparency tissue, which is 
made with Indian Ink dissolved and filtered with extreme care. 
It is sensitized by floating upon a solution of neutral or normal 
bichromate of potash and dried in the dark. 
The negative should be masked by means of black paper, with 
an aperture of the desired shape, to include as much of the picture 
as may be wished for. 
The picture should be printed strongly, and will require con- 
siderably more exposure than if to be developed for transfer to 
paper: the glasses being cut the proper size for the lantern holder, 
should be carefully cleaned and coated with a solution made as 
follows: Gelatine one ounce, water nineteen ounces, chrome alum 
twenty grains ; with this, coat the plate by pouring on as if collodion, 
and allow to run off at one corner. The glasses may be prepared - 
any time before-hand, and when dry are fit for use. 
When the latent picture is taken from the pressure frame, turn 
